national center for energy management and building ... · task 8: reduced energy use through...

FINAL REPORT NCEMBT 061101

REDUCED ENERGY USE THROUGH REDUCED INDOOR CONTAMINATION IN RESIDENTIAL BUILDINGS

NOVEMBER 2006

Wenhao Chen, Graduate Research Assistant Zhi Gao, Graduate Research Assistant Jianshun S. Zhang PhD, Principal Investigator Syracuse University Douglas Kosar, Principal Investigator Christine E. Walker, PhD, Senior Research Engineer University of Illinois at Chicago Davor Novosel National Center for Energy Management and Building Technologies

FINAL REPORT NCEMBT-061101

NATIONAL CENTER FOR ENERGY MANAGEMENT AND BUILDING TECHNOLOGIES TASK 8: REDUCED ENERGY USE THROUGH REDUCED INDOOR CONTAMINATION IN RESIDENTIAL BUILDINGS

November 2006

Prepared B : y Wenhao Chen, Graduate Research Assistant Zhi Gao, Graduate Research Assistant Jianshun S. Zhang PhD, Principal Investigator Syracuse University Douglas Kosar, Principal Investigator Christine E. Walker, PhD, Senior Research Engineer University of Illinois at Chicago Davor Novosel National Center for Energy Management and Building Technologies Prepared For: U.S. Department of Energy William Haslebacher Project Officer / Manager This report was prepared for the U.S. Department of Energy Under Cooperative Agreement DE-FC26-03GO13072

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NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof.

NATIONAL CENTER FOR ENERGY MANAGEMENT AND BUILDING TECHNOLOGIES CONTACT Davor Novosel Chief Technology Officer National Center for Energy Management and Building Technologies 601 North Fairfax Street, Suite 250 Alexandria VA 22314 703-299-5633 [email protected] www.ncembt.org

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TABLE OF CONTENTS EXECUTIVE SUMMARY.............................................................................................................................................1 1. PROJECT OBJECTIVE............................................................................................................................................3 2. BACKGROUND....................................................................................................................................................4 3. METHODOLGY.....................................................................................................................................................5

3.1 Overview of Technologies and Air Cleaners Selected for Evaluation.................................................................5 3.2 Experimental Methods for Particulates and VOCs Removal Test......................................................................7

3.2.1 Review of Literature and Existing Test Standards ....................................................................................7 3.2.2 Test Procedures.....................................................................................................................................8 3.2.3 Test Facility ...........................................................................................................................................9 3.2.4 Testing of Particulates and VOCs..........................................................................................................10 3.2.5 Test Specimen.....................................................................................................................................12 3.2.6 Calculation of CADR and Removal Efficiency ........................................................................................12 3.2.7 Sampling Locations.............................................................................................................................15 3.2.8 Instrumentation for Sampling and Analysis..........................................................................................16 3.2.9 Uncertainty Analysis ...........................................................................................................................17

3.3 Measurement Methods for Other Performance Parameters ..........................................................................17 3.3.1 Flow Rate Measurements....................................................................................................................17 3.3.2 Noise Level Measurements for Portable Air Cleaners............................................................................18 3.3.3 Power Consumption Measurements ....................................................................................................19 3.3.4 Pressure Drop Measurements for In-duct Air Cleaners .........................................................................20

4. RESULTS ..........................................................................................................................................................21 4.1 Airflow Rates of Portable Air Cleaners..........................................................................................................21 4.2 Noise Levels of Portable Air Cleaners...........................................................................................................22 4.3 Power Consumptions of Portable Air Cleaners .............................................................................................22 4.4 Results of Particulate and VOC Contaminants Removal Tests .......................................................................24

4.4.1 Product P1 ..........................................................................................................................................24 4.4.2 Product P2 ..........................................................................................................................................28 4.4.3 Product P3 ..........................................................................................................................................31 4.4.4 Product P4 ..........................................................................................................................................35 4.4.5 Product P5 ..........................................................................................................................................38 4.4.6 Product P6 ..........................................................................................................................................41 4.4.7 Product D1..........................................................................................................................................43 4.4.8 Product D2..........................................................................................................................................46

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5. DISCUSSION ....................................................................................................................................................50 5.1 Test Method Development ..........................................................................................................................50

5.1.1 VOCs + Particles Test vs. Particles Only Test.........................................................................................50 5.1.2 Comparisons with AHAM/ASHRAE Ratings ..........................................................................................51 5.1.3 Uncertainties ......................................................................................................................................52

5.2 Technology and Product Evaluation .............................................................................................................52 5.2.1 Quantification Of Ozone Emission From Electronic/Ionizer Air Cleaners ................................................52 5.2.2 Removal of Particulates.......................................................................................................................53 5.2.3 Removal of VOCs.................................................................................................................................56

5.3 Effectiveness of Tested Air Cleaners for IAQ Control .....................................................................................59 5.3.1 The Single-zone Model........................................................................................................................59 5.3.2 Effectiveness in Concentration Reduction............................................................................................60 5.3.3 Energy Savings and Cost Benefit ..........................................................................................................65

6. CONCLUSIONS .................................................................................................................................................69 6.1 Air Cleaner Performance .............................................................................................................................69 6.2. System Design Considerations...................................................................................................................70 6.3 Air Cleaner Installation Considerations........................................................................................................71

6. REFERENCES....................................................................................................................................................73 APPENDIX A: DETAILED SPECIFICATIONS OF SELECTED AIR CLEANERS .................................................................75 APPENDIX B: “PULL-DOWN” TEST PROCEDURE.....................................................................................................77 APPENDIX C: COMPARISON OF TESTED AIR CLEANERS FOR REMOVING HEXANE, ISO-BUTANOL, 2-BUTANONE, DECANE AND TETRACHLOROETHYLENE..................................................................................................................89 APPENDIX D: EXAMPLE ENERGY COST CALCULATION BY STEADY-STATE METHOD ...................................................91

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LIST OF FIGURES Figure 1. Conceptual schematic of “pull-down” test method ....................................................................................9 Figure 2 Test chamber with modified recirculation loop and in-duct testing section...................................................9 Figure 3 Empty chamber characterization .............................................................................................................14 Figure 4 Noise level measurement set-up in acoustic chamber ...............................................................................19 Figure 5 Measured power consumption for product P5...........................................................................................23 Figure 6 Chamber conditions during testing of product P1 (without pre-filter) .........................................................24 Figure 7 Concentration decay of VOCs and SF during testing of product P1 (without pre-filter)6 ...............................25 Figure 8 Concentration decay of particles during testing of product P1 (without pre-filter) .......................................25 Figure 9 Chamber conditions during testing of product P1 (make-up with pre-filter) ................................................26 Figure 10 Concentration decay of VOCs and SF during testing of product P1 (make-up with pre-filter)6 ....................27 Figure 11 Concentration decay of particles during testing of product P1 (make-up with pre-filter) ...........................27 Figure 12 Chamber conditions during testing of product P2 ...................................................................................29 Figure 13 Concentration decay of VOCs and SF during testing of product P26 .........................................................29 Figure 14 Concentration decay of particles during testing of product P2 .................................................................30 Figure 15 Chamber conditions during testing of product P3 ...................................................................................32 Figure 16 Concentration decay of VOCs and SF during testing of product P36 .........................................................32 Figure 17 Concentration decay of particles during testing of product P3 .................................................................33 Figure 18 Ozone generation during testing of product P3 .......................................................................................34 Figure 19 Chamber conditions during testing of product P4 ...................................................................................35 Figure 20 Concentration decay of VOCs and SF6 during testing of product P4.........................................................35 Figure 21 Concentration decay of particles during testing of product P4 .................................................................36 Figure 22 Possible Emissions from Product P4 ......................................................................................................37 Figure 23 Chamber conditions during testing of product P5 ...................................................................................38 Figure 24 Concentration decay of VOCs and SF during testing of product P56 .........................................................38 Figure 25 Concentration decay of particles during testing of product P5 .................................................................39 Figure 26 Ozone generation during testing of product P5 .......................................................................................40 Figure 27 Chamber conditions during testing of product P6 ...................................................................................41 Figure 28 Concentration decay of VOCs and SF during testing of product P66 .........................................................41 Figure 29 Concentration decay of particles during testing of product P6 .................................................................42 Figure 30 Chamber conditions during testing of product D1 ...................................................................................44 Figure 31 Concentration decay of VOCs and SF during testing of product D16 .........................................................44 Figure 32 Concentration decay of particles during testing of product D1.................................................................45 Figure 33 Chamber conditions during testing of product D2 ...................................................................................47

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Figure 34 Concentration decay of VOCs and SF during testing of product D26 .........................................................47 Figure 35 Concentration decay of particles during testing of product D2.................................................................48 Figure 36 VOC + Particle Test vs. Particle Only Test (marked with *) ........................................................................50 Figure 37 Ozone concentration during testing of products P3 and P5: Measurement vs. Calculation........................53 Figure 38 Measured removal efficiency vs. particle size..........................................................................................54 Figure 39 Average CADR and Std/Ave. CADR for portable air cleaners....................................................................55 Figure 40 Measured Removal Efficiency vs. VOC Vapor Pressure............................................................................57 Figure 41 Calculated percentage reductions in concentration for the base-case of 0.5 ACH of total air exchange ....62 Figure 42 Calculated percentage reductions in concentration for base-case of 0.35 ACH total air exchange............63 Figure 43 Calculated percentage reductions in concentration for base-case of 0.1 ACH total air exchange ..............64

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LIST OF TABLES Table 1 Summary of Selected Air Cleaners for Testing ..............................................................................................6 Table 2 Comparisons between ANSI/AHAM AC-1-2002 and ANSI/ASHRAE Standard 52.2-1999 ............................7 Table 3 Components of challenge VOC mixture and their properties........................................................................10 Table 4 Sources, indoor concentration level and exposure limit of challenge VOCs..................................................11 Table 5 Flow Rate Measurement Results for Portable Air Cleaners ..........................................................................21 Table 6 Noise Level Measurement Results for Portable Air Cleaners .......................................................................22 Table 7 Power Consumption Measurement Results for Portable Air Cleaners ..........................................................23 Table 8 Calculated CADR and Single-pass Efficiency for Product P1 (without pre-filter) ...........................................26 Table 9 Calculated CADR and Single-pass Efficiency for Product P1 (make-up with pre-filter)..................................28 Table 10 Calculated CADR and Single-pass Efficiency for Product P2 .....................................................................31 Table 11 Calculated CADR and Single-pass Efficiency for Product P3 .....................................................................34 Table 12 Calculated CADR and Single-pass Efficiency for Product P4 .....................................................................37 Table 13 Calculated CADR and Single-pass Efficiency for Product P5 .....................................................................40 Table 14 Calculated CADR and Single-pass Efficiency for Product P6 .....................................................................43 Table 15 Calculated CADR and Single-pass Efficiency for Product D1.....................................................................46 Table 16 Calculated CADR and Single-pass Efficiency for Product D2.....................................................................49 Table 17 Comparisons with AHAM Certified CADR Numbers for Portable Air Cleaners .............................................51 Table 18 Comparisons with ASHRAE Rated MERV Values for In-duct Air Cleaners ...................................................51 Table 19 Ozone Generation Rate and Maximum Concentration during Test for Product P3 and P5 ...........................53 Table 20 Comparisons of Tested Air Cleaners for Particulate Removal ....................................................................56 Table 21 Comparisons of Tested Air Cleaners for VOCs Removal.............................................................................58 Table 22 Energy Cost Comparison Based on Steady-State Method for Syracuse, NY................................................67 Table 23 Energy Cost Comparison Based on Steady-State Method for Chicago, IL ..................................................67

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EXECUTIVE SUMMARY

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EXECUTIVE SUMMARY According to the Freedonia Group, the consumer market for air cleaners, ranging from portable (room) to duct mounted (whole house) devices, grew 34% over a 5-year period to reach $395 million in 2004, and is estimated to reach $515 million by 2008. Homeowners, however, have only limited information available regarding their performance, especially for the combined removal of volatile organic compounds (VOCs) and particulates. A standard method of test for the removal efficiency of air cleaning devices under such conditions is lacking as well.

In this project, six “off the shelf” portable and two in-duct devices have been evaluated. Results are reported for their initial effectiveness to remove particulates and VOCs concurrently. All the tests were performed in a stainless steel environmental chamber. The devices were tested using a “pull-down” test procedure with simultaneous injection of potassium chloride particles ranging in diameter from 0.10 to 11µm and a mixture of eight representative VOCs. Other important parameters, including ozone emission, power consumption, noise level and pressure drop (across in-duct devices), were also measured.

The tested products utilize different technologies for gas and particulate removal including sorption, media filtration, ultraviolet-photocatalytic oxidation (UV-PCO), electronic precipitation and air ionization. The potential effectiveness and energy benefit of using such devices to clean recirculated air to decrease the outdoor air intake and reduce the ventilation-related energy costs are briefly discussed and compared. Some considerations are also provided for engineering improvements of the air cleaners along with further research needs, including methods for extrapolating the chamber results to real homes.

The major findings from the testing and follow-up analysis are:

Media filtration and electronic precipitation are two effective methods to remove indoor particulate contaminants. The single portable electronic air cleaner tested had better performance (Clean Air Delivery Rate (CADR), removal efficiency and cost) than other portable air cleaners claiming the use of HEPA filters, but generated significant amounts of ozone. None of the four portable air cleaners claiming the use of HEPA filters approached a removal efficiency of ≥ 99.97%. The measured efficiencies ranged from around 50% to 80%. Further investigation revealed that the frames allowed some air to by-pass the HEPA filters. The tested ionizer unit, which features no fan and thus is quiet, only had very modest removal capacity for particulates while generating very significant amounts of ozone.

Sorption and UV-photocatalytic oxidation are two effective methods to remove indoor VOC contaminants, although most of off-the-shelf products are based on sorption technology. Only one UV-PCO in-duct air cleaner was tested and its performance, in terms of initial removal efficiency and cost, could not compete with an in-duct air cleaner with approximately 12 pounds of sorbent media. The tested ionizer unit without fan had no significant removal effect for all the tested VOCs. The removal efficiency for a specific VOC is related to its properties. For sorption technology, a heavier and low-volatility compound is generally expected to have a higher absorbability on activated carbon than a lighter and more volatile compound. For UV-PCO technology, the removal efficiency was found to be more closely related to the functional group of the chemicals.

The proposed test method worked well for portable air cleaners with nominal airflows of typically less than 400 cubic feet per minute (CFM). For in-duct air cleaners tested under rated operating airflow rates from 600 to 2000 CFM, accurate determination of CADR was difficult. A smaller recirculation flow rate (< 400 CFM) might improve the resolution of the test method if a reliable model were available to extrapolate the performance measured at a low airflow rate to high

EXECUTIVE SUMMARY

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airflow rate(s). No significant difference was observed for particulate removal between tests with particle injection only and with simultaneous injection of particles and VOCs.

An analysis was performed to compare the energy cost between ventilation and use of a portable air cleaner using the simple steady-state model. Two cities, Syracuse, NY and Chicago, IL, were selected for analysis. Results indicate that there are significant savings using the best available air cleaner to replace the mechanical ventilation if particulates, toluene (or VOCs with vapor pressure smaller than 150 mmHg) or formaldehyde were the target pollutants. However, even the best portable air cleaner tested costs more than mechanical ventilation to provide the same clean air exchange rate for dichloromethane due to the low removal efficiency. In general, an air cleaner would need to perform better than $1.2/CADR (in Syracuse) or $3.75/CADR (in Chicago) for a target pollutant to obtain the energy cost benefit compared with mechanical ventilation

1. PROJECT OBJECTIVE

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1. PROJECT OBJECTIVE In this project, eight air cleaning devices were tested for their effectiveness in removing VOCs and particulates. Other important parameters, including ozone emission, power consumption, noise level and pressure drop across the in-duct devices, were also measured.

The specific goals of this project were to:

Utilize existing environmental chamber facilities at the Building Energy and Environmental Systems Laboratory (BEESL) at Syracuse University (SU) for an initial round of tests on selected portable (room) and duct mounted (whole house) residential air cleaning devices.

Delineate performance results from this first round of testing.

Provide some considerations for product improvements and installation.

The outcomes of this research contribute to the current knowledge of:

Standard test method development for combined particulate and VOCs removal;

Database of actual performance of air cleaners beyond the general claim of manufacturers;

Influence of product design and installation on the performance of air cleaners.

2. BACKGROUND

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2. BACKGROUND In general, indoor pollutants can be divided into three major groups: particles (mists, dust, pollen, bio-particles etc.), gaseous contaminants (volatile organic compounds, combustion gases, etc.) and radioactive gases (radon, etc.). Particles have been well recognized as a major class of indoor pollutants for a long time. Typical sources include tobacco smoke, use of unvented combustion appliances, cooking, cleaning, use of aerosol sprays, human and animal dander and outdoor air. The sizes of particles from different sources vary widely. For example, many of the particles of microbiologic origin tend to be larger than 1 µm in aerodynamic diameter, with some exceeding 10 µm, while most of the particle mass in tobacco smoke is contained within particles with a diameter between 0.1 – 1.0 µm (Fisk et al., 2002). Particulate pollutants may cause allergic response, irritation of the eyes and/or respiratory tissues and more serious chronic effects such as cancer and decreased lung function. Health effects from exposure to particulate pollutants may vary widely depending on the size, chemical composition and concentrations of particles present, the frequency and duration of exposure and individual sensitivity. Volatile organic compounds (VOCs), which have received more attention in recent years, represent another major class of indoor pollutants. Hundreds of VOCs have been found in indoor environments. Typical sources include new building materials and furnishings, office equipments, consumer products, maintenance materials, tobacco smoke, and outdoor air. VOC pollutants may cause offensive odors, skin and membrane irritations, allergic reactions and chronic effects including cancer. Health effects from exposure to VOC pollutants in the air may vary widely depending on the types and concentrations of chemicals present, the frequency and duration of exposure, and individual sensitivity (Godish, 2001).

Providing fresh outdoor air through controlled ventilation systems is the straightforward approach being applied to homes to accomplish dilution of contaminants indoors. Increasingly though, air cleaning technologies/devices to treat recirculated air are available to homeowners as an additional or alternative means of improving the indoor air quality (IAQ). The homeowner and consumer markets for air cleaners have grown 34% over a 5-year period to reach $395 million in 2004, according to the Freedonia Group, and with continued growth are estimated to reach $515 million by 2008. The air cleaners in these markets range from portable (room) to duct mounted (whole house) devices. Unfortunately, validated performance is limited and test standards are pending (for sorbent media and in-duct filters) or non-existent (for combined particulate and VOCs removal). Air cleaner evaluations are needed to assist the engineering, manufacturing, and contracting fields with their development and application of these technologies for residential buildings.

3. METHODOLGY

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3. METHODOLGY 3.1 OVERVIEW OF TECHNOLOGIES AND AIR CLEANERS SELECTED FOR EVALUATION Different types of air cleaning/purification technologies are often used for different types of indoor pollutants. Technologies used in air cleaning devices for removing indoor VOC contaminants mainly include:

Sorption filtration (physi-sorption and/or chemi-sorption), which removes gaseous contaminants from indoor air by adsorption on solid adsorbent material (activated carbon, zeolite, etc.). This is the most commonly used technology. Most off-the-shelf commercial products are based on this technology although the type of sorbent media may be different.

UV-Photocatalytic Oxidation (PCO), which removes gaseous contaminants via chemical reactions on a catalyst (such as titanium dioxide) surface under UV irradiation.

Air ionization (or plasma decomposition), which creates charged air molecules and forms cluster ions (radicals) to decompose VOCs by a complex series of oxidation reactions.

Ozone oxidation, which removes VOCs by reaction with ozone.

Botanical air cleaning, which refers to the removal of gaseous contaminants from indoor air by plants and their soils through biological processes.

Here, “removing” generally refers to the concentration decrease of target VOC pollutants in indoor air. They can either be physically removed from air by adherence to, and retention on, the solid sorbents (at least temporarily) or be chemically converted to other substances such as CO2 and water as desired final products.

Technologies and devices for removing indoor particulate contaminants mainly include:

Mechanical filtration, which removes particulate contaminants from indoor air by filtration media via several mechanisms (such as interception, impaction, and Brownian motion/diffusion) depending on the size and characteristics of the particles.

Electrostatic precipitator, which first electrically charges the particles as they pass through a strong electric field and then immediately collects them on a series of flat plates.

Mechanical filtration with charged-media and/or methods to pre-charge particles, which first electrically charges the particles and then immediately collects them on charged filter media.

Ion generator (Ionizer), which also uses static charges to remove particle contaminants from indoor air. However, this type of devices typically does not have a fan unit but generates tiny ionic breezes instead. They act by charging the particles in the room so that they can fall out of air and be attracted to indoor surfaces (wall, floor, table tops, etc.). In some cases, these devices may contain a collector to attract the charged particles back to the unit.

Air cleaning devices can also be grouped according to their installation position. For residential houses, two types of devices are readily available: standalone (portable) room air cleaners (including desktop units) and in-duct devices (filters). Portable air cleaners can be easily operated in a room with flexible time schedules but only clean the air in a limited area (e.g. up to several connected rooms without obstructions to air flow). In-duct devices (filters) work for the whole house, but need to be installed in the air handling system and function only when the air handling system is operating.

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In this study, the air cleaners were selected based on the following considerations:

The selected products covered major types of technologies used for indoor VOCs and particulate removal.

The selected products were representative of both portable air cleaners and in-duct devices should be included.

The popularity of products in the marketplace (such as ranking in consumer reports and popular websites used in shopping for air cleaners) was also considered.

Products with published (or available) test data from national research labs (i.e. NIST) were given priority so that test results can be compared later.

For ozone oxidation, our previous research (Chen et al., 2005) showed that an ozone generator was likely to result in unsafe ozone concentration levels and its removal efficiencies for most indoor VOCs could not compete with even moderate ventilation. In addition, EPA strongly advises against the use of ozone generators due to ozone emission concerns (EPA 2000). For botanical air cleaning, only prototype products exist and no commercial devices are readily available in market. Therefore, these two technologies were excluded in the product selection.

(The portable off-the-shelf products based on UV-PCO were very limited. No UV-PCO products with a popular brand name were found. Some products, although advised as UV-PCO device, were not designed properly and therefore not selected.

A total of eight commercial off-the-shelf products were selected, of which six were portable air cleaners and two were in-duct devices. The type and technology category of selected products are summarized in Table 1. More detailed specifications of selected products are shown in Appendix A.

Table 1 Summary of Selected Air Cleaners for Testing

Major Technology for removing VOCs

Major Technology for removing particulates

Product Type

Device No.

Purchase Price Sorption

Filtration UV-PCO Ionization Mechanical

Filtration Electrostatic precipitator

Mechanical filtration with

charged particles

and/or media

Ionizer

P1 $249

P2 $795

P3 $499

P4 $565 P5 $349

Portable

P6 $4701

D1 $510 In-duct D2 $14001

Note: Product P6 and D2 were directly provided by manufacturers. Sales prices for US market are estimated.

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3.2 METHODS OF TEST FOR REMOVAL OF PARTICULATES AND VOCS 3.2.1 Review of Literature and Existing Test Standards

Standards reviewed for testing particulate removal performance of air cleaners include ANSI/AHAM Standard AC-1-2002 for portable room air cleaners and ANSI/ASHRAE Standard 52.2-1999 for in-duct air cleaners. Comparisons of some key experimental parameters are summarized in Table 2. It should be noted that testing methods for other product characteristics besides the particulate removal are also specified in these standards (i.e. resistance to airflow for in-duct devices in ASHRAE Standard 52.2-1999), but not included in Table 2.

Table 2 Comparisons between ANSI/AHAM Standard AC-1-2002 and ANSI/ASHRAE Standard 52.2-1999

ANSI/AHAM Standard AC-1-2002 ANSI/ASHRAE Standard 52.2-1999

Application category

Portable household electric room air cleaners

General ventilation in-duct air-cleaning devices

Test apparatus Sealed test chamber Test duct rig Test aerosol Cigarette smoke (0.10 – 1.0µm

diameter) Fine dust (0.5 – 3.0µm diameter) Pollen ((5 – 11µm diameter)

Polydisperse solid-phase (dry) potassium chloride (KCL) particles over the 0.30 – 10µm diameter size range

Test method Pull-down: Aerosol generator is stopped before turning on the air cleaner and the concentration decay from its initial value is measured

Constant source: Aerosol generator runs continuously during the experiment. Particle concentrations at both upstream and downstream of the air cleaner are measured (sequentially).

Performance parameters reported

CADR (Clean Air Delivery Rate) for cigarette smoke, fine dust and pollen respectively (initial performance only)

PSE (Particle size removal efficiency) curve for 12 size range over 0.30 – 10µm diameter (for the clean device and for the device at each of five dust loading stages) and MERV (Minimum Efficiency Reporting Value)

Note: Cigarette smoke, fine dust and pollen are tested in three separate tests in ANSI/AHAM AC-1-2002.

To our best knowledge, there is no established standard for testing the effectiveness of air cleaners for removal of VOCs by either portable or in-duct devices. The proposed ASHRAE Standard 145.1P, which describes a test procedure for a composite rating (using percent removal efficiency and removal capacity) of a small media sample when it is challenged under steady-state conditions by a number of gaseous contaminants, is the one closest to final approval. However, it only addresses the media performance and therefore cannot be used for rating the overall performance of an air cleaner. The proposed ASHRAE Standard 145.2P, which describes a laboratory test method for assessing the performance of gas-phase in-duct air cleaning devices, is still in the development stage. In addition, the test VOC concentrations proposed in these standards (i.e. 100 ppm) are much higher than typical indoor levels. Therefore, they are not reflecting the real application for indoor environment, but rather serve as a way to compare different media/filters.

Research papers regarding the test method and results of air cleaners were also reviewed (Chen et al. 2005, Daisey et al. 1989, Emmerich et al. 2001, Hanley et al. 1994a, Hanley et al. 1994b, Hodgson et al. 2005, Niu et al. 1998, Offermann et al. 1985, Reed et al. 2002, Reed et al. 2005, VanOsdell 1994). It was found that the “pull-down” test method was more commonly used in evaluating portable air cleaners for both VOC and particulate removal. CADR was often reported. When the flow rate passing through the air cleaner was known and a well-mixed single-zone model could be applied to the test condition, single-

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pass removal efficiency can be further calculated. Cigarette smoke or burning-incense smoke (in the size range of 0.1 – 3.0 µm) has been used as testing particles.

For in-duct devices, the “constant-source” test method was more commonly used. The fractional (single-pass) removal efficiency was often reported. Solid potassium chloride (KCl) was often used as testing aerosol. KCl particles with diameters ranging from 0.01 to 3 µm and from 0.3 to 10 µm have been generated and tested. Toluene or decane have been selected as the representative challenge VOC for both portable and in-duct air cleaners when a single VOC was used. Some VOC mixtures representing different chemical function groups of indoor VOCs have also been tested.

Experimental evaluations of air cleaning devices for control of multiple indoor pollutants (both particulates and VOCs) are limited. A total of 27 commercially available portable air cleaners were tested in Hong Kong Polytechnic University using burning-incense smoke and toluene as testing particles and VOC, respectively (Niu et al. 1998). However, tests were performed on the smoke and toluene separately instead of simultaneously. In addition, the initial concentrations in chamber for toluene ranged from 20 ppm to 50 ppm, which were much higher than typical indoor levels (<100 ppb per compound). To our best knowledge, no paper has reported results of simultaneous removal of particulate and VOCs by different air cleaners under controlled experimental conditions.

Interference between particulate and VOC contaminants may occur in indoor air under certain circumstances. Some air cleaners may produce new types of pollutants when removing the target type of pollutants. For example, some particles (i.e., carbon particles from combustion processes) are efficient adsorbers (and therefore carriers) of many organic compounds. Air cleaners with particulate removal filter may remove such particles from the air and then re-emit VOCs from the collected particles (Offermann et al., 1985). Also, removal of some specific VOCs (i.e. d-Limonene) by the oxidation technology (i.e. via reaction with ozone) may result in other VOC by-products and significant secondary ultra-fine particle (<0.1 µm) formation (Weschler 2000, Wainman et al. 2000). Although it is beyond the scope of this project to investigate this topic in detail, this information helped choose the experimental conditions and facilitated a better understanding of the test results.

3.2.2 Test Procedures

As most of selected products were portable air cleaners, the “pull-down” chamber test method was selected and used for both portable and in-duct air cleaners. Figure 1 shows the conceptual schematic of this method. It consists of three test periods with the chamber operating under the full-recirculation mode: injection period, static period and dynamic period. The injection of known amount of contaminants into the experimental system followed by a quasi-static period, results in stable, initially high concentration levels. The time when the air cleaner is turned on is defined as time zero, at which the dynamic period begins. Using the measured concentration decay rate, the clean air delivery rate (CADR) can then be calculated for each VOC and particles of different sizes. The detailed step-by-step procedure is reported in Appendix B. Only the initial “out of the box” performance of air cleaners was tested using this procedure.

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Figure 1. Conceptual schematic of “pull-down” test method

3.2.3 Test Facility

All of the tests for characterizing the performance of air cleaners for removing particulates and VOC contaminants were carried out in a full-scale stainless steel environmental chamber depicted in Figure 2. The chamber has a dimension of 12 ft long x 7.1 ft wide x 10 ft high (3.66 m long x 2.16 m wide x 3.05 m high) and an interior volume of 852 ft3 (24.1 m3). Detailed description of this chamber facility and its performance evaluation (air mixing, control accuracy, etc.) can be found in Herrmann et al. (2003). The chamber system was modified to include a separate recirculation loop with a variable speed stainless steel fan. This modification avoided contamination of the chamber HVAC system by injected particles during the test. However, it resulted in no temperature or relative humidity control after switching the chamber from HVAC system to the modified recirculating loop at the beginning of injection period, although these values were continuously monitored during the test. For in-duct air cleaners, an in-duct testing section with bypass was constructed and installed. The bypass channel allowed the air to bypass the air cleaner testing section during the injection and static period.

Figure 2 Test chamber with modified recirculation loop and in-duct testing section

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3.2.4 Testing of Particulates and VOCs

Polydisperse solid-phase (dry) potassium chloride (KCl) particles were selected as challenging aerosols and produced by a TSI Model 8108 Large-particle Aerosol Generator. The size range and amount of particles injected into the test chamber can be controlled by setting a suitable KCl solution concentration and injection time. In the current study, a 30% KCl solution and an injection time of approximate 1 min were used, which provided sufficiently high initial concentrations over the diameter size range of approximately 0.10 to 11µm.

A mixture of eight VOCs (Table 3) was used as the challenge VOC. This mixture covered the major chemical categories and a wide range of molecular weights (MW), boiling points (BP) and vapor pressures (VP). Table 4 summarizes the potential sources, example indoor concentration levels and exposure limits of selected VOCs. Since VOC concentrations in indoor environment are typically low (in the order of parts per billion), initial concentrations of 1 mg/m3 were targeted for all VOCs in this project except for formaldehyde that had a target initial concentration of 2 mg/m3. The higher initial concentration for formaldehyde was due to the relatively low detection limit of the formaldehyde monitor (about 40 ppb). Formaldehyde was generated by heating solid paraformaldehyde inside the chamber. Other VOCs were introduced into the chamber by vaporizing a known amount of VOC liquid during the injection period.

The initial contaminant concentrations were not exactly the same for each air cleaner test. However, this did not affect the performance evaluation tests because the effectiveness of an air cleaner was derived from the concentration decay from its initial measured value.

Table 3 Components of the challenge VOC mixture and their properties

Chemical Category

Chemical Name Molecular Formula

Molecular Weight

Boiling Point (oC)

Approximate Vapor Pressure at 25oC (mm Hg)

Compound Included in

ASHRAE Std 145.1P

n-Hexane C6H14 86.2 69 151 yes Alkane n-Decane C10H22 142.3 174 1.25 no

Aromatic Toluene C7H8 92.1 111 28.4 yes Dichloromethane CH2Cl2 84.9 40 435 yes Chlorocarbon Tetrachloroethylene C2Cl4 165.8 121 18.6 yes

Alcohol iso-Butanol C4H10O 74.1 108 9 yes Ketone 2-Butanone C4H8O 72.1 80 78 yes Aldehyde Formaldehyde CH2O 30.0 -19 3840 yes

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Table 4 Sources, typical indoor concentration levels and exposure limits of challenge VOCs

Chemical Name Potential sources Typical indoor concentrations1

Exposure limit2 EPA HAPs3

n-Hexane Floor materials, furnishings, paints and coatings, wood products

0.28 ppb PEL: 50ppm TLV: 50ppm CREL: 7000 µg/m3 (1983 ppb)

X

n-Decane Floor adhesive, wood stain, floor wax, carpet, room freshener

0.97 ppb NE

Toluene Adhesives, caulks and sealants, floor materials, furnishings, office machines, paints and coatings, cigarette smoke


X

Dichloromethane (Methylene chloride)

6.4 ppb PEL: 500ppm TLV: 50ppm CREL: 400 µg/m3

(115 ppb)

X

Tetrachloroethylene Caulks and sealants, miscellaneous materials


X

iso-Butanol PEL: 100ppm TLV: 75ppm CREL: NE

2-Butanone Floor finish, photocopier 6.4 ppb PEL: 200ppm TLV: 200ppm CREL: NE

Formaldehyde Combustion appliances, tobacco smoke, wood products, furnishings, floor materials, insulation products, paints and coatings, indoor air reactions

55 ppb PEL:0.75ppm TLV: 0.3ppm (Ceiling limit) CREL: 33 µg/m3 (27 ppb)

X

Notes:

(1) Mean concentrations in new single-family houses (for 2-butanone) or existing residences (for other VOCs) reported by Hodgson et al. (2003) were adopted as the typical indoor concentrations.

(2) “PEL” is Permissible Exposure Limit set by OSHA ,“ TLV ” is Threshold Limit Value set by HCGIH, CREL is chronic reference exposure level established by California EPA OEHHA for indoor air(http://www.oehha.ca.gov/air/chronic_rels/AllChrels.html), and “ NE” means exposure limit not established;

(3) Compounds included in EPA Hazardous Air Pollutants (HAP) lists were indicated by “X”;

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3.2.5 Test Specimen

All the air cleaners were newly purchased and tested as received without modification, except for product P1 for which tests were conducted with and without the thin activated carbon pre-filter.

For portable air cleaners, each air cleaner was positioned at the same place inside the chamber and operated at its maximum operational setting. For the in-duct devices, each device was installed in the in-duct testing section right before the dynamic test period. The airflow rate through the device was controlled by the recirculating fan and periodically monitored by a velocity meter.

3.2.6 Calculation of CADR and Removal Efficiency

Three parameters have been commonly used to quantify the performance of air cleaning devices: single-pass efficiency (conversion), clean air delivery rate (CADR), and effectiveness of the device (Nazaroff, 2000).

Single-pass efficiency (η) represents the fraction of pollutants removed from the air stream as it passes through the device. It is defined as:

inCoutCinC

inGCoutCinCG −

=−

=)(

η (1)

where,

Cin = contaminant concentration at the inlet of air cleaner, mg/m3 for VOC and number of particles/cm3 for particulates.

Cout = contaminant concentration at the outlet of air cleaner, mg/m3 for VOC and number of particles /cm3 for particulates.

G = airflow rate through the air cleaner, CFM or m3/h.

CADR represents the “effective” clean airflow rate delivered by the air cleaner. It is defined as:

dEGCADR ⋅⋅= η (2)

where,

Ed = short-circuiting factor of the air cleaner, CCE ind = , where C is average concentration

in the test chamber (Ed = 1 under well-mixed condition).

The effectiveness of the device (ε) represents the fractional reduction in pollutant concentration that results from application of an air cleaner. It is defined as:

refCctrlCrefC −

=ε (3)

where,

Cref = indoor contaminant concentration without use of air cleaning device, mg/m3 for VOC and number of particles/cm3 for particulates.

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Cctrl = indoor contaminant concentration when the air cleaning device is used, mg/m3 for VOC and number of particles/cm3 for particulates.

The effectiveness directly indicates the benefit of using an air cleaner. An effectiveness of 1 (Cctrl = 0) represents ideal performance and an effectiveness of 0 (Cctrl = Cref) represents a complete lack of reduction in pollutant concentrations. The value of the effectiveness not only depends on the performance of the air cleaner itself, but also the effectiveness of other pollutant removal mechanisms (i.e. ventilation).

The performance parameter measured directly by the “pull-down” test method is CADR. The analysis is based on the well-mixed single zone model. Assuming that the air is well mixed in chamber and the contaminant removal mechanisms other than air cleaning (e.g. surface deposition effect and chamber leakage effect) are the same with and without air cleaner operating and can be characterized by a first-order rate constant kn, the mass conservation of contaminant in the “pull-down” test can be written as:

CCADRVkdtdCV n ⋅+−= )( , (C = C0 at t = 0) (4a)

or

CekCV

CADRnk

dtdC

⋅−=⋅+−= )( (4b)

where,

V - volume of the testing chamber system, ft3 or m3,

kn – contaminant concentration decay rate without air cleaner operating (chamber effects), min-1 or h-1,

ke – total contaminant concentration decay rate with air cleaner operating, min-1 or h-1,

C0 – Initial contaminant concentration inside the chamber, mg/m3 for VOC and number of particles/cm3 for particulates.

To characterize the chamber effects on the air cleaner test results for VOCs (mainly a possible sink effect), an empty chamber test was conducted first. Figure 3 shows the measured concentrations of each VOC and tracer gas (SF6). Normalized concentrations (i.e. concentration divided by the initial concentration at time t = 0) were used to facilitate the comparison. The decay rate of SF6 was 0.033 ACH (corresponding to 0.5 CFM), indicating that chamber leakage rate was acceptable. The decay rate of each individual VOC only had moderate variations (0.033 – 0.048 ACH) and was close to that of SF6, indicating small sink effect of the chamber under the experimental conditions. Therefore the chamber sink effect was neglected and only the chamber leakage rate (characterized by SF6 decay rate for each test) was considered when calculating kn.

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0.01

0.1

1

10

-3 -2 -1 0 1 2 3 4 5 6

Time (hr)

Nor

mal

ized

C

once

ntra

tion

from

G

C/M

S an

d ga

s m

onito

r

Dichloromethane Hexane 2-Butanoneiso-Butanol Toluene TetrachloroethyleneDecane Formaldehyde SF6

Under full-recirculation mode

Figure 3 Empty chamber characterization

To characterize the chamber effects on the air cleaner test results for particulates (mainly surface deposition), a natural decay period (around 25 minutes) was defined before turning on the air cleaner for each test. The measured concentration decay during this period was used to calculate kn. This allowed for a more accurate characterization of the particle natural decay rate for each test.

If CADR does not change during the test period, an analytical solution can be obtained from Equation (4) as:

tekeCt

VCADR

nkeCC −⋅=

+−⋅= 0

)(0 (5)

CADR can then be determined by linear regression of ln (C/C0) vs. t from the measured concentration decay curve:

CADR = V(ke-kn) (6)

Experimental results indicate that Equation (5) described the particulate concentration decay well for all air cleaners tested. However, for some air cleaners, a change of CADR was observed during the 6 hour (6 h) dynamic period for certain VOCs. This made the direct fitting of all experimental data to Equation (5) inappropriate. An equivalent average CADR number over test period (CADR_6h) was defined for these cases and calculated as:

T

T dtt

VhCADR

nkeC

T

T Cdt ∫⋅+−

⋅=

∫ 0)6_(

00 (7)

Where

T = the length of dynamic test period (T =6 h).

Once the CADR has been calculated and the airflow rate through the air cleaner has been measured, the removal efficiency can then be calculated by dividing the CADR by the airflow rate through the air cleaner. This calculated removal efficiency was the same as the single-pass efficiency defined in Equation

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(1) since the air in the chamber was well-mixed. If Equation (7) was used in calculating the average CADR over 6 hrs, the calculated removal efficiency would be the average removal efficiency over the test period corresponding to the average CADR.

The step-by-step data analysis procedure for particulates is summarized as follows:

1. Sum the measured particulate number concentrations to five diameter ranges: 0.1 – 1µm and 1 - 2µm from LASAIR APC 1003 measurements, 0.523 – 3.162µm, 3.162 – 5.233µm and 5.233 – 11.548µm from TSI APS 3321 measurements. This allows easier comparison with AHAM certified CADR numbers (0.1 - 1µm tobacco smoke, 0.5 – 3µm dust and 5 – 11µm pollen);

2. Calculate kn by linear regression of ln (C/C0) vs. t from concentration decay curve measured during natural decay period (after injection but before turning on the air cleaner);

3. Calculate ke by linear regression of ln (C/C0) vs. t from concentration decay curve measured after turning on the air cleaner (dynamic period);

4. Calculate CADR according to Equation (6);

5. Calculate removal efficiency by dividing the CADR by the measured airflow rate through the air cleaner.

The step-by-step data analysis procedure for VOCs is summarized as follows:

6. Calculate kn based on the measured tracer gas concentration decay;

7. Calculate ke by linear regression of ln (C/C0) vs. t from measured concentration decay curve after turning on the air cleaner (dynamic period);

8. Calculate CADR according to Equation (6);

9. Justify whether the calculated CADR number is significant. A CADR value larger than 1.5 (corresponding to 0.1 ACH) is regarded as significant;

10. If the CADR number is significant and the linear regression of ln (C/C0) vs. t fits the experimental data well, report the CADR value directly;

11. If the CADR number is significant but the linear regression of ln (C/C0) vs. t cannot fit the measured concentration decay curve well (i.e. regression coefficient R2 < 0.85), fit (C/C0) vs. t with another selected curve format (i.e. double exponential decay) and calculate the CADR_6h according to Equation (7).

12. Determine the removal efficiency by dividing the calculated CADR value by the measured airflow rate through the air cleaner.

3.2.7 Sampling Locations

Equation (5) relates the CADR to the decay rate of the average indoor contaminant concentration. The concentration measured at the return duct can be used to represent the average concentration in the chamber if complete mixing is achieved inside the test chamber (ASTM Standard D 6670-01, 2001). The complete mixing condition has been verified during the chamber-commissioning test (Herrmann et al. 2003). In this study, the recirculating airflow rate was provided by the system recirculating fan during the portable air cleaner tests was equivalent to an ACH of 9. During the in-duct air cleaner tests the approximate ACH was 49. In addition, the operation of a portable air cleaner inside the chamber during

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the test period enhanced the air movement and resulted in better mixing. These high recirculating flow rates were sufficient for achieving complete mixing in the chamber.

For ozone and VOCs, the sampling location was in the return duct right out of the outlet of the chamber (approximate 6” from the chamber outlet face) to represent the average concentration inside the chamber. For particles, it was difficult to sample isokinetically within the short duct length of current system, so the sampling location was in the middle of the chamber and 1.6 m above the floor (typical height of breathing zone for a standing person).

3.2.8 Instrumentation for Sampling and Analysis

An INNOVA 1312 Photoacoustic Multi-gas Monitor was used for online measurements of the concentration of total hydrocarbon as toluene equivalent (TVOCtoluene), the concentration of formaldehyde (Cformal), and the concentration of tracer gas (SF6). The monitor is based on the photoacoustic infrared detection method. For TVOCtoluene, the sensitivity and response factor of the instrument for different compounds were different, so the readings from the gas monitor were only used as semi-quantitative measures to monitor the change of TVOC concentrations over time and how they differed for different air cleaning devices.

For quantification of individual VOCs other than formaldehyde, sorbent tubes (two layers: 200 mg Tenax TA + 100 mg Carboxen 569) were used to take air samples. These sampling tubes were then analyzed by an Automated Thermal Desorber (ATD) – Gas Chromatography /Mass Spectrometer (GC/MS) system to determine the concentration of each individual compound. The configurations of the ATD – GC/MS system for VOC analysis were as follows:

Thermal desorption unit: Perkin-Elmer ATD 400

2-Stage desorb with inlet split & outlet split

Primary desorption: 280 °C (10 min)

Secondary desorption: Low 0°C, High 300 °C (Hold 28 min)

GC-MS: Perkin-Elmer Autosystem GC

GC column: Elite 624, N9316201 (30 m × 0.25 mm id × 1.4 µm film thickness)

Oven: 50°C (hold 1.5 min), 5°C /min to 120°C, 10°C /min to 230°C (hold 1.5 min)

Detector: MS

Quantification: Individual response factor for individual VOCs

A TSI Model 3321 Aerodynamic Particle Sizer Spectrometer (APS) and a LASAIR Model 1003 Aerosol Particle Counter (APC) from PMS Inc. were used for measurement of particle concentrations. The TSI APS 3321 has 52 sizing channels ranging from 0.5 to 20 µm in aerodynamic sizing. It determines particle size by measuring the time of flight of the particle. Results were directly reported in terms of aerodynamic diameter for TSI APS 3321 measurements, although they could be converted to physical diameter knowing the density (1.98 g/cm3 for KCl particles) and dynamic shape factor of the testing aerosols. The LASAIR APC 1003 is an optical particle counter and has eight sizing channel with thresholds at 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 1.0 and 2.0 µm. It determines particle size based on the intensity of the particle’s scattered light.

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A chemiluminescene ozone analyzer (API model 265) was used to measure ozone concentration, which has a precision of 0.5% of reading and a detection limit of 0.6 ppb.

The correspondent SOPs (Standard Operation Procedures kept in lab) were followed for the operation of each instrument.

3.2.9 Uncertainty Analysis

There were two types of uncertainties: uncertainty related to concentration measurements of particulates and VOCs during the test and uncertainty related to regression (curve fitting) during the data analysis.

Uncertainty of initial concentration measurement did not affect the calculated CADR values as the CADR was calculated from the dimensionless concentration decay. In addition, assuming that the accuracy of measurement instrument remained the same during the entire test period (i.e. no drift) and any systematic errors of the instrument were within the percentage error, they would be cancelled out when computing concentration decay rates and thus would not affect the CADR. The major source of uncertainty in CADR calculation arises from the number of measurement data points and the degree of fit of the decay curves to the data points. For CADR calculated from direct fitting to exponential concentration decay, the uncertainty was characterized by regression statistical analysis and reported as 95% confidence interval (CI). For a few cases where only CADR_6h can be calculated (mainly for dichloromethane and formaldehyde), the uncertainty was difficult to determine and therefore not reported.

Uncertainty of single-pass efficiency was then computed by adding the uncertainty of calculated CADR and flow rate measurement together in quadrature.

3.3 MEASUREMENT METHODS FOR OTHER PERFORMANCE PARAMETERS

3.3.1 Flow Rate Measurements

Flow rate is a very important factor that influences the “overall” performance of the air cleaner. When two air cleaners have the same single pass removal efficiency, the device with higher flow rate will circulate more air and therefore have a better overall performance.

Flow rate measurements were performed at each operation level setting for all portable room air cleaners except for P5. Product P5 was an ionizer with no fan unit but generated a small ionic breeze. Accurate measurement of the flow rate, although possible, was difficult using the experimental setup and therefore was not conducted. The velocities and cross section area at air intake (or outlet) were measured and the flow rate was then calculated. A velocity meter (Veloci-Calc 8347, TSI Inc.) was used to measure velocities. It has the following specifications:

measurement range: 0-6000 ft/min;

resolution: 1ft/min;

accuracy: 3 % of reading or ± 3 ft/min, whichever is greater (applies to 30-6000 ft/min).

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Measurements were conducted according to the following procedure:

1. Measure the dimensions of air intake (or outlet) and compute the corresponding cross-section area;

2. Turn on the room air cleaner and set its operation level;

3. Take measurement at each transverse points, record reading and then move the velocity probe to the next transverse point. At least nine point measurements should be taken;

4. Calculate the average value of velocity measurement;

5. Calculate the product of cross-section area and the average velocity to get the flow rate value;

6. Change operation level set of the room air cleaner, repeat step (3)-(5) until all operation levels are tested.

The uncertainty of flow rate measurement was estimated to ± 15% due to the irregular shape of air intake (or outlet) and non-uniformity of velocity for some portable air cleaners.

For in-duct air cleaners, the cross section area of the duct was measured. The reading from the velocity meter (Veloci-Calc 8347, TSI Inc.) placed in the middle of the duct was periodically checked during the test and the average flow rate was then calculated. The uncertainty of flow rate measurement for in-duct air cleaners was estimated to be ± 7% based on the standard deviation/average flow rate monitored during the tests.

3.3.2 Noise Level Measurements for Portable Air Cleaners

For portable room air cleaners, their impact on the sound comfort is also an important performance parameter. The noise level of a room air cleaner must not be too high to disturb the occupants. Generally, whether an occupant considers the background noise to be acceptable or not depends on two factors. First is the perceived loudness of the noise relative to that of normal activities. Second is the quality of the background noise.

The sound pressure levels (SPL) were measured at each operation level setting for all portable room air cleaners. All the tests were carried out in an acoustic chamber (Figure 4), which has an interior volume of 1166 ft3 (33 m3). It is a hemi-anechoic chamber and its sound attenuating enclosure is obtained by lining the walls, ceilings, and floor with anechoic wedges. A sound level meter (Model 1900, Quest Technologies) was used for noise measurement. It has the following specifications:

measurement range: 0 to 140 dBA,

resolution: 0.1 dBA.

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Figure 4 Noise level measurement set-up in acoustic chamber

As there was no standard test method available for measuring the noise level of portable air cleaners, an existing standard (ANSI S12.10-2002) was adopted as a reference. The air cleaner was placed in the middle of chamber on the steel plate (4 ft x 4 ft). A microphone sitting on a 3.2 ft (1 m) stand was placed at four different points (evenly distributed around the air cleaner at 1 m away) sequentially to take the SPL measurements. This experimental setup was in accordance with the ANSI Standard S12.10-2002. The traditional A-weighted sound pressure level (dBA) was used in this method. The A-weighted sound pressure level is a single number measure of the relative loudness of noise that is used extensively in outdoor environmental noise standards.


1. Turn on the sound meter;

2. Put the air cleaner in the middle of chamber on the steel plate;

3. Turn on the air cleaner and set the operation level;

4. Put the microphone at the 1st measurement point and close the chamber;

5. Wait until the reading from sound level meter is steady;

6. Record the SPL measure for each octave (from 125 Hz to 16000 Hz) and the mean A-weighted SPL value;

7. Repeat steps (5) - (6) for the 2nd, 3rd and 4th measurement points;

8. Repeat steps (3) - (8) for each operation level.

It should be noted that the measured SPL included the effect of the chamber background SPL level (LA,chamber = 23 dBA according to the measurement).

3.3.3 Power Consumption Measurements

Good indoor air quality should be achieved in an energy efficient manner. Energy consumption is a significant concern when choosing air cleaners.

The power consumption was measured at each operational setting for all portable room air cleaners. An energy meter (Model PLM-1, Electronic Design Ltd.) was used for measuring the power consumption. It has the following specifications:

measurement range: 0.1-2800 W,

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resolution: 0.1W,

accuracy: ± 0.5% of actual value.


1. Connect the air cleaner to be tested to the energy meter;

2. Turn on the air cleaner and set its operational level;

3. Take measurement and record readings continuously for 30 minutes at 0.5 minutes interval;

4. Calculate the average value and its standard deviation for the last 10 minutes (20 readings) obtained from step (3);

5. Change operation level set of the room air cleaner, repeat step (3)-(4) until all operating levels are tested.

For in-duct air cleaners, product D1 contained filters only and thus had no direct power consumption although it would increase system fan power consumption due to its pressure drop. Product D2 had direct power consumption due to the use of UV lamps, which was measured continuously using the energy meter (Model PLM-1, Electronic Design Ltd.) during the test.

3.3.4 Pressure Drop Measurements for In-duct Air Cleaners

For in-duct air cleaners, the pressure drop across the device is an important design parameter. A larger pressure drop requires a fan with higher static pressure and increases both initial cost and energy costs. In fact, pressure drop limitations often eliminate the use of deep carbon beds in typical residential applications. The pressure drop across the in-duct device was continuously monitored during the test by a differential pressure transducer (Ashcroft Model CXLdp) installed across the test box, which has the following specifications:

measurement range: 0 – 10 in. W.G.;

resolution: 0.01 in. W.G.;

accuracy: 0.8% of full-scale.

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4. RESULTS 4.1 AIRFLOW RATES OF PORTABLE AIR CLEANERS Results of the airflow rate measurements for portable air cleaners are summarized in Table 5 including available data from manufacturers. Measured values were comparable to the specifications given by manufacturers except for P4, which had a maximum relative difference of 110 CFM at the operational level IV. For air cleaners with a fan unit, the airflow rates ranged from 200 to 400 CFM at maximum operational settings. Reducing the operational settings reduced the airflow rate. However, the degree of airflow decrease varied widely for different air cleaners. For example, the ratio of airflow rate between maximum and minimum operation settings was as high as 6.7 for product P4 and only 1.7 for product P3.

Table 5 Results of Airflow Rate Measurements for Portable Air Cleaners

Airflow Rate at Different Operational Settings (CFM) Device No.

Level I (Minimum)

Level II Level III Level IV Level V Level VI (Maximum)

P1 129 N/A 182 N/A N/A 249 P2 37 (37) 62 (70) 97 (115) 122 (145) 149 (170) 227 (240) P3 233 (225, 280) N/A 299 (275,340) N/A N/A 387 (365, 410) P4 58 (88) N/A 74 (117) 137 (247) N/A 386 (450) P5 - N/A - N/A N/A - P6 57 N/A 78 162 N/A 232 (180)

Notes:

(1) Values in “ ( ) ” were nominal flow rates given by manufacturers. For product P3, two different values were given in the product sales brochure and operation guide respectively and both of them were listed;

(2) Product P5 was an ionizer with no fan unit and the flow rate at each operation level was not measured (indicated by “ - ”);

(3) “N/A” means “Not Applicable” (no such operational setting).

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4.2 NOISE LEVELS OF PORTABLE AIR CLEANERS Results of the noise level measurements for portable air cleaners are summarized in Table 6 including available data from manufacturers. Product P5 was an ionizer with no fan unit and thus operated very quietly (the measured SPL was the same as the chamber background). For air cleaners with a fan unit, noise level (sound pressure level) ranged from 47 to 59 dBA at the maximum operational setting. Reducing the operational setting reduced the noise level.

Table 6 Results of the Noise Level Measurements for Portable Air Cleaners

SPL Level at Different Operational Settings (dBA) Device No.

Level I (Minimum)


P1 45 N/A 50 N/A N/A 57 P2 28 36 46 49 52 59 P3 39 N/A 43 N/A N/A 50 P4 26 (32) N/A 28 39 N/A 57 (68) P5 23 N/A 23 N/A N/A 23 P6 24 N/A 25 36 N/A 47 (47)

Notes:

(1) Chamber background SPL level was 23 dBA;

(2) Values in “ ( ) ” were noise levels given by manufacturers;

(3)“N/A” means “Not Applicable” (no such operation level).

4.3 POWER CONSUMPTIONS OF PORTABLE AIR CLEANERS Results of power consumption measurements for portable air cleaners are summarized in Table 7 including available data from manufacturers. Measured values were generally comparable to the specifications given by manufacturers except for P2 operating at lower speed levels. The readings were stable during measurements expect for P5, for which a cyclic characteristic was observed during the measurement at low and medium operational levels (Figure 5). Results indicate that product P5 required the least power and the power consumption varied from 51 to 233 watts for other air cleaners at the maximum operational setting. In addition, we had another unit (same model as product P3) from a previous research project, so we performed side-by-side measurements for these two units. Results indicate large differences in the power consumption of different units of the same model (50 W vs. 110 W).

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Table 7 Results of the Power Consumption Measurements for Portable Air Cleaners

Power Consumption at Different Operational Settings (Watts) Device No.

Level I (Minimum)


P1 48 N/A 70 N/A N/A 136 P2 29 (85) 56 (120) 93 (150) 118 (170) 162 (205) 233 (215) P3 47 (47) N/A 53 (64) N/A N/A 67 (90) P4 24 (35) N/A 29 50 N/A 124 (120) P5 2.4 (< 10) N/A 3.7 (< 10) N/A N/A 7.2 (< 10)

P6 24 N/A 25 32 N/A 51

Notes:

(1) Values in “ ( ) ” are power consumptions given by manufacturers;

(2) Product P6 was designed to operate at 220 V. A transformer (220 V to 120 V) was used and its power consumption was also included in the measured value.

012345678

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Number of Readings

Pow

er C

onsu

mpt

ion

(Wat

t)

Level I (low) Level III (medium) Level VI (high)

Figure 5 Measured power consumption for product P5

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4.4 RESULTS OF PARTICULATE AND VOC CONTAMINANTS REMOVAL TESTS

4.4.1 Product P1

Product P1 has a cylindrical design. The passes through the thin activated carbon pre-filter, HEPA filter and gas and odor adsorption filter (sorbent mixture blends charcoal, potassium permanganate and zeolite) sequentially and exits through the outlet on the top of the unit.

As stated in Section 3.2.5, the first test was run without the activated carbon pre-filter. Figure 6 shows the measured temperature and relative humidity during the experiment. As there was no temperature and RH control after switching from HVAC system to the modified recirculation loop, the temperature increased and the relative humidity decreased due to the heat generation from the hot plate used for vaporizing VOCs (– 2 to – 1 hr), the operation of recirculating fan, particle counters (-2 to 6 hr) and operation of the air cleaner (0 to 6 hr) itself. Figure 7 shows the measured concentration decay for each VOC and the tracer gas (SF6). Normalized concentrations (i.e. concentration divided by the initial concentration at time t = 0) were used to facilitate the comparison. The chamber leakage rate characterized by the decay of SF6 was 0.019 ACH and its influence was considered when calculating the CADR. The particulate concentration decays measured by TSI APS 3321 and LASAIR APC 1003 are shown in Figure 8. Table 8 lists the calculated CADR and single pass efficiency for each VOC and particulate diameter range.

20

22

24

26

28

30

-3 -2 -1 0 1 2 3 4 5 6

Time from turning on the air cleaner (hr)

Mea

sure

d C

ham

ber

Tem

pera

ture

(o C

)

0

20

40

60

80

100

Mea

sure

d C

ham

ber R

H

(%)

TemperatureRelative humidity

Figure 6 Chamber conditions during testing of product P1 (without pre-filter)

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0.01

0.1

1

10

-3 -2 -1 0 1 2 3 4 5 6Time from turning on the air cleaner (hr)

Nor

mal

ized

C

once

ntra

tion

from

G

C/M

S an

d ga

s m

onito

r


Figure 7 Concentration decay of VOCs and SF6 during testing of product P1 (without pre-filter)

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(a) TSI APS 3321 Measurement

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(b) LASAIR 1003 APC Measurement

Figure 8 Concentration decay of particles during testing of product P1 (without pre-filter)

4. RESULTS

NCEMBT-061101

26

Table 8 Calculated CADR and Single-pass Efficiency for Product P1 (without pre-filter)

VOC CADR (CFM) η (%) Particulate CADR

(CFM) η (%)

Decane 87 ± 7 35 ± 6 0.1 – 1µm 167 ± 1 67 ± 10

Tetrachloroethylene 116 ± 4 46 ± 7

LASAIR 1003 APC Measurement 1 - 2 µm 182 ± 2 73 ± 11

Toluene 105 ± 6 42 ± 7 0.523 – 3.162 µm 167 ± 1 67 ± 10

Iso-Butanol 115 ± 2 46 ± 7 3.162 – 5.233 µm 177 ± 2 71 ± 11

2-Butanone 92 ± 11 37 ± 7

TSI 3321 APS Measurement

5.233 – 11.548 µm 187 ± 3 75 ± 11

Hexane 91 ± 14 36 ± 8

Dichloromethane 7 3

Formaldehyde 5 2

PSL equivalent diameter used in LASAIR 1003 APC measurement and aerodynamic diameter used in TSI 3321 APS measurement

Note: CADR and efficiency were reported with ± 95% confidence interval (CI) when measured data could be directly fitted by exponential decay. The second test was a make-up test performed on the same unit with a new activated carbon pre-filter added. Figure 9 shows the measured temperature and relative humidity during the experiment. The trend was similar to that of the first test. Figure 10 shows the measured concentration decay for each VOC and the tracer gas (SF6). Normalized concentrations (i.e. concentration divided by the initial concentration at time t = 0) were used to facilitate the comparison. The chamber leakage rate characterized by the decay of SF6 was 0.067 ACH and its influence was considered when calculating the CADR. The particulate concentration decays measured by TSI APS 3321 and LASAIR APC 1003 are shown in Figure 11. Table 9 lists the calculated CADR and single pass efficiency for each VOC and each particulate diameter range.

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Figure 9 Chamber conditions during testing of product P1 (make-up with pre-filter)

4. RESULTS

NCEMBT-061101

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Figure 10 Concentration decay of VOCs and SF6 during testing of product P1 (make-up with pre-filter)

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Figure 11 Concentration decay of particles during testing of product P1 (make-up with pre-filter)

4. RESULTS

NCEMBT-061101

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Table 9 Calculated CADR and Single-pass Efficiency for Product P1 (make-up with pre-filter)

VOC CADR (CFM) η (%) Particulate CADR (CFM) η (%)

Decane 128 ± 6 51 ± 8 0.1 – 1µm 163 ± 1 65 ± 10



Toluene 138 ± 7 55 ± 9 0.523 – 3.162 µm 159 ± 2 64 ± 10

Iso-Butanol 138 ± 16 56 ± 10 3.162 – 5.233 µm 167 ± 3 67 ± 10

2-Butanone 127 ± 13 51 ± 9


5.233 – 11.548 µm 184 ± 5 74 ± 11

Hexane 123 ± 17 49 ± 10

Dichloromethane 10 4

Formaldehyde 3 1


Note: CADR and efficiency were reported with ± 95% confidence interval (CI) when measured data could be directly fitted by exponential decay. Results indicate that the addition of the activated carbon pre-filter improved the removal efficiencies for decane, tetrachloroethylene, toluene, iso-butanol, 2-butanone and hexane (the average increase of removal efficiency was 13%), slightly increased the removal efficiency of dichloromethane (from 3% to 4%) and had no improvement on the removal efficiency of formaldehyde and particulates. The slightly decrease of removal efficiencies for formaldehyde and particulates during the make-up test might be due to the continuous use of the same unit. As for the removal of VOCs in general, results indicate that the removal efficiencies for most of injected VOCs (except dichloromethane and formaldehyde) were close and ranged from 49 to 57% (with the activated carbon pre-filter). For dichloromethane and formaldehyde, the concentration did not fit the exponential decay well and there were still significant amounts left at the end of the 6 hour dynamic period. The removal efficiencies for particles with different sizes were also close and ranged from 65 to 74%.

4.4.2 Product P2

Product P2 has a “sandwich” type modular housing design. The air is drawn into the unit by the centrifugal fan via two arched openings at the base, passes through the pre-filter, gas and odor adsorption filter (containing a 5-pound blend of granular activated carbon and potassium permanganate impregnated alumina), and HEPA filter sequentially and exits through the diffuser outlet on the top. This product has the best documentation of product design among air cleaners tested and comes with a manufacturer’s own certificate of performance (airflow rate and HEPA efficiency).

Figure 12 shows the measured temperature and relative humidity during the experiment. The temperature increased and relative humidity decreased as expected. Figure 13 shows the measured concentration decay for each VOC and the tracer gas (SF6). Normalized concentrations (i.e. concentration divided by the initial concentration at time t = 0) were used to facilitate the comparison. The chamber leakage rate characterized by the decay of SF6 was 0.041 ACH and its influence was considered when calculating the CADR. The particulate concentration decays measured by TSI APS 3321 and LASAIR APC 1003 are shown in Figure 14. Table 10 lists the calculated CADR and single pass efficiency for each VOC and each particulate diameter range.

4. RESULTS

NCEMBT-061101

29

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(o C

)

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)

Temperature

Relative humidity

Figure 12 Chamber conditions during testing of product P2

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/MS

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Figure 13 Concentration decay of VOCs and SF6 during testing of product P2

4. RESULTS

NCEMBT-061101

30

0.001

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0.1-0.2 um 0.2-0.3 um 0.3-0.4 um 0.4-0.5 um0.5-0.7 um 0.7-1.0 um 1.0-2.0 um


Figure 14 Concentration decay of particles during testing of product P2

4. RESULTS

NCEMBT-061101

31

Table 10 Calculated CADR and Single-pass Efficiency for Product P2


Decane 78 ± 7 34 ± 6 0.1 – 1µm 160 ± 1 70 ± 11



Toluene 95 ± 2 42 ± 6 0.523 – 3.162 µm 161 ± 1 71 ± 11

Iso-Butanol 96 ± 7 42 ± 7 3.162 – 5.233 µm 164 ± 2 72 ± 11

2-Butanone 91 ± 7 40 ± 7


5.233 – 11.548 181 ± 7 80 ± 11

Hexane 91 ± 6 40 ± 7


Formaldehyde 77 ± 3 34 ± 5


Note: CADR and efficiency were reported with ± 95% confidence interval (CI) when measured data could be directly fitted by exponential decay.

Results indicate that the removal efficiencies for most of injected VOCs (except dichloromethane) were close and ranged from 34 to 43%. For dichloromethane, the removal efficiency was 9%. The removal efficiencies of particles with different sizes were also close and ranged from 70 to 80%.

4.4.3 Product P3

Product P3 is an electronic air cleaner. The air is drawn into the unit by the fan from one side, passes through the pre-filter, the electronic cell (ionization section + collector plates), and the thin activated carbon post-filter sequentially, and exits through the other side of the air cleaner.

Figure 15 shows the measured temperature and relative humidity during the experiment. The temperature increased and relative humidity decreased as expected. Figure 16 shows the measured concentration decay for each VOC and tracer gas (SF6). Normalized concentrations (i.e. concentration divided by the initial concentration at time t = 0) were used to facilitate the comparison. The chamber leakage rate characterized by the decay of SF6 was 0.073 ACH and its influence was considered when calculating the CADR. The particulate concentration decays measured by TSI APS 3321 and LASAIR APC 1003 are shown in Figure 17. Table 11 lists the calculated CADR and single pass efficiency for each VOC and each particulate diameter range.

4. RESULTS

NCEMBT-061101

32

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-3 -2 -1 0 1 2 3 4 5 6

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(o C

)

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H (%

)TemperatureRelative humidity


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-3 -2 -1 0 1 2 3 4 5 6

Time (hr)

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Con

cent

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n fr

om

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/MS

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4. RESULTS

NCEMBT-061101

33

0.001

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-3 -2 -1 0 1 2 3 4 5 6

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0.523 - 3.162 um 3.162 - 5.233 um 5.233 - 11.548 um


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-3 -2 -1 0 1 2 3 4 5 6Time (hr)

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0.1-0.2 um 0.2-0.3 um 0.3-0.4 um 0.4-0.5 um0.5-0.7 um 0.7-1.0 um 1.0-2.0um



4. RESULTS

NCEMBT-061101

34



Decane 22 6 0.1 – 1µm 308 ± 3 80 ± 12

Tetrachloroethylene 6 2


Toluene 7 2 0.523 – 3.162 µm 348 ± 3 90 ± 14

Iso-Butanol 5 1 3.162 – 5.233 µm 460 ± 6 119 ± 18

2-Butanone 1.4 ± 0.3 0.4 ± 0.1


5.233 – 11.548 µm 454 ± 18 117 ± 18

Hexane 1.9 ± 0.3 0.5 ± 0.1

Dichloromethane 0.6 ± 0.1 0.2 ± 0.0

Formaldehyde 0.7 ± 0.1 0.2 ± 0.0



The maximum removal efficiency for VOCs was only 6% (decane), suggesting that the thin activated carbon filter alone might not be sufficient for odor and VOCs control. It was observed that heavier compounds were removed faster than lighter compounds (decane > toluene ≈ tetrachloroethylene > iso-butanol > hexane ≈ 2-butanone > formaldehyde ≈ dichloromethane). As for the particulates, the removal efficiencies were large and ranged from 80 to 119% for different size particles. The efficiencies larger than 100% could be due to the measurement uncertainty.

There was significant amount of ozone generated during the test (Figure 18) and the maximum concentration was 53 ppb at the end of the 6-hour dynamic period. Further tests are needed to determine whether the ozone generation occurs during the initial use period only or over the entire lifetime of the air cleaner.

0

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-3 -2 -1 0 1 2 3 4 5 6

Time (hr)

Ozo

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in

cham

ber (

ppb)

Measured by M265AO3 Analyzer

Figure 18 Ozone generation during testing of product P3

4. RESULTS

NCEMBT-061101

35

4.4.4 Product P4

Product P4 is mainly a filter type of unit with particles negatively charged before reaching the filters to maximize filter effectiveness. The air is drawn into the unit from openings at the base, passes through ion brushes (for charging the particles) and filter kits (HEPA filter and then enhanced activated carbon filter) and exits. There are three identical filter kits and they are placed at two sides and top, respectively.

Figure 19 shows the measured temperature and relative humidity during the experiment. The temperature increased and relative decreased as expected. Figure 20 shows the measured concentration decay for each VOC and tracer gas (SF6). Normalized concentrations (i.e. concentration divided by the initial concentration at time t = 0) were used to facilitate the comparison. The chamber leakage rate characterized by the decay of SF6 was 0.061 ACH and its influence was considered when calculating the CADR. The particulate concentration decays measured by TSI APS 3321 and LASAIR APC 1003 are shown in Figure 21. Table 12 lists the calculated CADR and single pass efficiency for each VOC and each particulate diameter range.

20

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4. RESULTS

NCEMBT-061101

36

0.001

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-3 -2 -1 0 1 2 3 4 5 6

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4. RESULTS

NCEMBT-061101

37



Decane 188 ± 11 49 ± 8 0.1 – 1µm 197 ± 2 51 ± 8



Toluene 216 ± 17 56 ± 10 0.523 – 3.162 µm 192 ± 3 50 ± 8

Iso-Butanol 246 ± 35 64 ± 13 3.162 – 5.233 µm 208 ± 5 54 ± 8

2-Butanone 223 ± 18 58 ± 10


5.233 – 11.548 µm 225 ± 5 58 ± 9

Hexane 232 ± 15 60 ± 10


Formaldehyde 28 7



Results indicate that the removal efficiencies for most of the injected VOCs (except dichloromethane and formaldehyde) were high and ranged from 49 to 64%. Removal of dichloromethane and formaldehyde was quick during the first 10 minutes but became much slower during the later period, resulting in an overall 6-hour average efficiency of 9% and 7% respectively. In addition, we observed that the decrease of the TVOC sensor reading from on-line gas monitor measurement was much slower and stabilized at a fairly high level compared to individual VOC measurement results from GC/MS analysis, suggesting that there might be some other compounds. However, we could not detect any major peaks other than the injected VOCs using the current analytical method on GC/MS. We further performed a test with the air cleaner inside the chamber but without VOC injections. The TVOC sensor reading from gas monitor increased when the air cleaner was turned on (Figure 22), suggesting that the air cleaner itself might be an emission source. As for the particles, the removal efficiencies for different sizes were close and ranged from 50 to 58%.

0

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)

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6

9

SF6 (

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)

TVOC as toluene SF6

Recirculation mode with air cleaner inside chamber

Air cleaner onAir cleaner off

Figure 22 Possible Emissions from Product P4

4. RESULTS

NCEMBT-061101

38

4.4.5 Product P5

Product P5 is a popular brand of ionizer. It is compact and has no fan unit, although it can generate a small ionic breeze during operation.

Figure 23 shows the measured temperature and relative during the experiment. The temperature increased and relative humidity decreased as expected. As product P5 lacks a fan, the temperature increase during the 6-hour dynamic period was smaller compared to tests of the other products. Figure 24 shows the measured concentration decay for each VOC and tracer gas (SF6). Normalized concentrations (i.e. concentration divided by the initial concentration at time t = 0) were used to facilitate the comparison. The chamber leakage rate characterized by the decay of SF6 was 0.029 ACH and its influence was considered when calculating the CADR. The particulate concentration decays measured by TSI APS 3321 and LASAIR APC 1003 are shown in Figure 25. Table 13 lists the calculated CADR for each VOC and each particulate diameter range. The single pass efficiency could not be calculated because the flow rate was not measured.

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4. RESULTS

NCEMBT-061101

39

0.0010.01

0.11

10100

100010000

-3 -2 -1 0 1 2 3 4 5 6Time (hr)

Num

ber C

once

ntra

tion

(#/c

m3 )

0.523 - 3.162 um 3.162 - 5.233 um 5.233 - 11.548 um


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0.1-0.2 um 0.2-0.3 um 0.3-0.4 um 0.4-0.5 um0.5-0.7 um 0.7-1.0 um 1.0-2.0um



4. RESULTS

NCEMBT-061101

40



Decane 0.4 ± 0.1 - 0.1 – 1µm 6 ± 0 -

Tetrachloroethylene 0.4 ± 0.1 -

LASAIR 1003 APC Measurement 1 - 2 µm 10 ± 0 -

Toluene 0.1 ± 0.1 - 0.523 – 3.162 µm 7 ± 0 -

Iso-Butanol 0.5 ± 0.2 - 3.162 – 5.233 µm 14 ± 0 -

2-Butanone 0.2 ± 0.1 -


5.233 – 11.548 µm 15 ± 1 -

Hexane 0.3 ± 0.1 -

Dichloromethane 0.1 ± 0.1 -

Formaldehyde 0.3 ± 0.1 -


Notes:

(1) CADR and efficiency were reported with ± 95% confidence interval (CI) when measured data could be directly fitted by exponential decay.

(2) (2) η could not be calculated because P5 has no fan unit and flow rate was not measured.

0

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-3 -2 -1 0 1 2 3 4 5 6Time (hr)

Ozo

ne c

once

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tion

in

cham

ber (

ppb)

Measured by M265AO3 Analyzer

Figure 26 Ozone generation during testing of product P5

Results indicate that product P5 had no significant removal of VOCs (maximum CADR was 0.5 or 0.035 ACH) and had only modest removal of particulates (CADR ranged from 6 to 15 for different size of particles). In addition, there was significant amount of ozone generated during the test (Figure 26) with the maximum concentration measured at 175 ppb at the end of 6-hour dynamic period.

4. RESULTS

NCEMBT-061101

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4.4.6 Product P6

Product P6 is a filter type of unit. It is the only one that has separate formaldehyde and VOC filters. Air is drawn into the unit via the opens around the front panel, passes through metallic pre-filter, HEPA filter, formaldehyde filter, VOCs filter and allergen filter sequentially, and exits though the outlet at the top of the unit. The air outlet also has adjustable air flow direction blades.

Figure 27 shows the measured temperature and relative humidity during the experiment. The temperature increased and relative humidity decreased as expected. Figure 28 shows the measured concentration decay for each VOC and tracer gas (SF6). Normalized concentrations (i.e. concentration divided by the initial concentration at time t = 0) were used to facilitate the comparison. The chamber leakage rate characterized by the decay of SF6 was 0.079 ACH and its influence was considered when calculating the CADR. The particulate concentration decays measured by TSI APS 3321 and LASAIR APC 1003 are shown in Figure 29. Table 14 lists the calculated CADR and single pass efficiency for each VOC and each particulate diameter range.

20

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Time (hr)

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4. RESULTS

NCEMBT-061101

42

0.001

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0.1-0.2 um 0.2-0.3 um 0.3-0.4 um 0.4-0.5 um0.5-0.7 um 0.7-1.0 um 1.0-2.0 um



4. RESULTS

NCEMBT-061101

43



Decane 115 ± 7 49 ± 8 0.1 – 1µm 142 ± 2 61 ± 9



Toluene 124 ± 6 54 ± 8 0.523 – 3.162 µm 135 ± 3 58 ± 9

Iso-Butanol 151 ± 37 65 ± 19 3.162 – 5.233 µm 141 ± 4 61 ± 9

2-Butanone 91 ± 14 39 ± 8


5.233 – 11.548 µm 150 ± 7 65 ± 10

Hexane 88 ± 19 38 ± 10

Dichloromethane 8 4




Results indicate that concentrations of most of injected VOCs (except dichloromethane) decayed exponentially and the calculated removal efficiencies ranged from 33 to 65%. There was still a significant amount of dichloromethane left at the end of test period and the calculated 6-hour average efficiency was 4%. As for the particles, the removal efficiencies for different sizes were close and ranged from 58 to 65%.

4.4.7 Product D1

Product D1 is a filter type in-duct device. It is a combination of a chemical and a particulate filter that uses MERV 15 particulate filter media and contains an equal blend by volume of potassium permanganate granular media and activated carbon granular media (total approximately 12 lb) for chemical filtration. Its dimensions are 24 in. wide, 24in. deep and 12 in high. The rated pressure drop is 0.56 – 0.7 in. w.g. at a face velocity of 500 pm (2000 cfm flow rate). This product is advertised for moderate to high load applications in commercial environments. Because the technologies employed are also suitable for residential applications, it was selected for this project.

The average flow rate measured during the test period was 659 CFM. The pressure drop measured was 0.1 in. w.g., which was only 1% of full-scale of the differential pressure (DP) sensor used during the test. A DP sensor with smaller measurement range will be used to improve the measurement accuracy during the next phase of the project. There was no direct power consumption of product D1. Figure 30 shows the measured temperature and relative humidity during the experiment. The relative humidity dropped to approximately 20% at the end of test, which was larger than that during the tests of portable air cleaner. Figure 31 shows the measured concentration decay for each VOC and tracer gas (SF6). Normalized concentrations (i.e. concentration divided by the initial concentration at time t = 0) were used to facilitate the comparison. The chamber leakage rate characterized by the decay of SF6 was 0.150 ACH, which was significantly larger than the leakage rate for any of the portable air cleaner tests. Although all of the seals and fittings were checked for tightness, this leakage rate could not be further reduced for this test. As the influence of chamber leakage is considered when calculating the CADR, test conditions were regarded as acceptable.

4. RESULTS

NCEMBT-061101

44

The particulate concentration decays measured by TSI APS 3321 and LASAIR APC 1003 are shown in Figure 32. Table 15 lists the calculated CADR and single pass efficiency for each VOC and each particulate diameter range. For VOCs other than formaldehyde, the CADR was calculated using the results from the first sorbent tube sample only (taken at 0.1 hr after turning on the air cleaner) and thus 95% CI could not be calculated. For particulates in the diameter range of 5.233 – 11.548 µm, the concentrations decayed to the detection limits before turning on the air cleaner due to the large recirculation flow rate. Therefore, CADR could not be calculated.

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Figure 30 Chamber conditions during testing of product D1

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Figure 31 Concentration decay of VOCs and SF6 during testing of product D1

4. RESULTS

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0.001

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(#/c

m3 )

0.523 - 3.162 um 3.162 - 5.233 um 5.233 - 11.548 um


0.001

0.01

0.1

1

10

100

1000

10000

-3 -2 -1 0 1 2 3 4 5 6

Time (hr)

Num

ber C

once

ntra

tion

(#/c

m3 )

0.1-0.2 um 0.2-0.3 um 0.3-0.4 um 0.4-0.5 um0.5-0.7 um 0.7-1.0 um 1.0-2.0 um


Figure 32 Concentration decay of particles during testing of product D1

4. RESULTS

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Table 15 Calculated CADR and Single-pass Efficiency for Product D1


Decane 482 73 0.1 – 1µm 555 ± 9 84 ± 6

Tetrachloroethylene 591 90


Toluene 588 89 0.523 – 3.162 µm 555 ± 7 84 ± 6

Iso-Butanol 511 78 3.162 – 5.233 µm 490 ± 13 74 ± 6

2-Butanone 604 92


5.233 – 11.548 µm - -

Hexane 599 91




Notes:

(1) CADR and efficiency were reported with ± 95% confidence interval (CI) when measured data could be directly fitted by exponential decay;

(2) For VOCs other than formaldehyde, the CADR was calculated using the results from the first sorbent tube sample only and thus 95% CI could not be calculated;

(3) For particulates in the diameter range of 5.233 – 11.548µm, the concentrations decayed to detection limit before turning on the air cleaner and thus the CADR could not be calculated.

Results indicate that product D1 was very efficient in removing both VOCs and particulates. Removal efficiencies ranged from 67 to 92% for injected VOCs and 74 to 85% for measurable particle diameter ranges.

4.4.8 Product D2

Product D2 has an overall dimension of 23.9 x 11.6 x 29 in. It has a 4 in. thick MERV 9 pleated filter for particulate filtration and a UV-PCO module for removal of VOCs. The UV-PCO module consists of a catalyst coated triangular honeycomb monolith and an array of UV lamps (six 368nm UVA lamps). The airflow passes through the particulate filter, UV lamps and the catalyst coated monolith sequentially. The range of nominal airflow rate suggested by the manufacturer is from 600 to 2000 CFM. The power consumption specified by manufacturer is 252 watts (2.1 amps at 120V and 60 Hz).

The average airflow rate measured during the test period was 667 CFM. The pressure drop was 0.02 in. w.g. and the average power consumption measured was 142 watts (RMS current of 1.2 amps at 120 V). Figure 33 shows the measured temperature and relative humidity during the experiment. Compared to product D1 test conducted under similar system conditions, a larger temperature increase (approximate 1.2oC) was observed due to the heat generated by the UV lamps. The decrease of relative humidity was similar to that in the D1 test and dropped to approximate 20% at the end of test. Figure 34 shows the measured concentration decay for each VOC and tracer gas (SF6). Normalized concentrations (i.e. concentration divided by the initial concentration at time t = 0) were used to facilitate the comparison. The chamber leakage rate characterized by the decay of SF6 was 0.159 ACH. As the influence of chamber leakage is considered when calculating the CADR, test conditions were regarded as acceptable.

4. RESULTS

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The particulate concentration decays measured by TSI APS 3321 and LASAIR APC 1003 are shown in Figure 35. Table 16 lists the calculated CADR and single pass efficiency for each VOC and each particulate diameter range. For particulates in the diameter range of 5.233 – 11.548 µm, the concentrations decayed to detection limit before turning on the air cleaner due to the large recirculation flow rate. Therefore, CADR could not be calculated.

20

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26

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32

-3 -2 -1 0 1 2 3 4 5 6

Time (hr)

Mea

sure

d C

ham

ber

Tem

pera

ture

(o C)

0

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60

80

100

Mea

sure

d C

ham

ber R

H (%

)


Figure 33 Chamber conditions during testing of product D2

0.01

0.1

1

10

-3 -2 -1 0 1 2 3 4 5 6

Time (hr)

Nor

mal

ized

con

cent

ratio

n fr

om G

C/M

S an

d ga

s m

onito

r


Figure 34 Concentration decay of VOCs and SF6 during testing of product D2

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0.001

0.01

0.1

1

10

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1000

10000

-3 -2 -1 0 1 2 3 4 5 6Time (hr)

Num

ber C

once

ntra

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(#/c

m3 )

0.523 - 3.162 um 3.162 - 5.233 um 5.233 - 11.548 um


0.001

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0.1-0.2 um 0.2-0.3 um 0.3-0.4 um 0.4-0.5 um0.5-0.7 um 0.7-1.0 um 1.0-2.0 um


Figure 35 Concentration decay of particles during testing of product D2

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Table 16 Calculated CADR and Single-pass Efficiency for Product D2


Decane 34 ± 2 5 ± 0 0.1 – 1µm 132 ± 2 20 ± 1



Toluene 40 ± 2 6 ± 1 0.523 – 3.162 µm 178 ± 1 27 ± 2

Iso-Butanol 98 ± 39 15 ± 6 3.162 – 5.233 µm 389 ± 9 58 ± 4

2-Butanone 52 ± 4 8 ± 1


5.233 – 11.548 µm - -

Hexane 13 ± 1 2 ± 0

Dichloromethane 4 ± 0 1 ± 0



Notes:

(1) CADR and efficiency were reported with ± 95% confidence interval (CI) when measured data could be directly fitted by exponential decay;

(2) (2) For particulates in the diameter range of 5.233 – 11.548µm, the concentrations decayed to detection limit before turning on the air cleaner and thus the CADR could not be calculated.

The removal efficiency varied from compound to compound for VOCs and ranged from 1 to 15%. In general, the alcohol, ketone and aldehyde tested (iso-butanol, 2-butanone and formaldehyde) were removed faster (η ≥ 7%) and the chlorocarbons (tetrachloroethylene and dichloromethane) had the smallest removal efficiency (η = 1%). For the two alkanes tested, the heavier compound (decane) had larger removal efficiency than the lighter one (hexane). As for the particulates, removal efficiencies ranged from 20 to 58% for measurable size ranges.

5. DISCUSSION

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5. DISCUSSION 5.1 TEST METHOD DEVELOPMENT

5.1.1 VOCs + Particles Test vs. Particles Only Test

Prior to formal tests, we performed some pilot tests in the empty chamber with simultaneous and separate injection of particles and VOCs, respectively. There was no significant difference regarding the trend of measured concentrations in these empty chamber tests, indicating that adsorption of VOCs by injected particles was negligible. Following the formal tests with combined injection of VOCs and particles, several air cleaners were tested with particle injection only to investigate whether injection of VOCs had influence on particulate removal by air cleaners. Results are shown in Figure 36 with results from particle only tests marked with “*”. There was no or only slight difference between results from VOC + particle tests and from particle only tests, suggesting that particulate removal would not be affected by VOC injections when using KCl as testing aerosols.

0

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CA

DR

- P2

Tes

t [C

FM]

0.1-1.0 um

0.1-1.0 um *

1.0-2.0 um

1.0-2.0 um*

0.523-3.162 um

0.523-3.162 um*3.162-5.233 um

3.162-5.233 um*

5.233-11.548 um

5.233-11.548 um*

0

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CA

DR

- P3

Tes

t [C

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0.1-1.0 um

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1.0-2.0 um

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0.523-3.162 um

0.523-3.162 um*

3.162-5.233 um

3.162-5.233 um*

5.233-11.548 um

5.233-11.548 um*

(a) Product P2 (b) Product P3

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- P4

Tes

t [C

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0.1-1.0 um0.1-1.0 um *1.0-2.0 um

1.0-2.0 um*0.523-3.162 um0.523-3.162 um*

3.162-5.233 um3.162-5.233 um*5.233-11.548 um

5.233-11.548 um*

0

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2 Te

st [C

FM] 0.1-1.0 um

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0.523-3.162 um

0.523-3.162 um*

3.162-5.233 um

3.162-5.233 um*

(c) Product P4 (d) Product D2

Figure 36 VOC + Particle Test vs. Particle Only Test (marked with *)

5. DISCUSSION

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5.1.2 Comparisons with AHAM/ASHRAE Ratings

Table 17 and Table 18 compare our measurement results with available AHAM and ASHRAE ratings, respectively. It should be noted that the test conditions/methods of current study were not exactly the same as those of AHAM or ASHRAE standards. Other than product P4, our test results are generally comparable with AHAM ratings. Our measured efficiency tends to be lower than that of the ASHRAE ratings, especially for large particles. One possible reason is that only 3.162 – 5.233 µm particles were counted in current study and removal efficiencies for particles larger than 5.233 µm might be larger. For product P4, our measured CADRs for all sizes of particles in both VOC + particle and particle only tests were significantly smaller than those of AHAM ratings. At this time we can only speculate that performance may vary from unit to unit even for the same model, as we noted when we compared results obtain in this Task for product P3 compared to previous tests conduct on the same model but a different unit.

Table 17 Comparisons with AHAM Certified CADR Numbers for Portable Air Cleaners

CADR (CFM) Product P1 Product P3 Product P4

Tobacco smoke (0.1 – 1.0 µm) 195 300 388 Dust (0.5 – 3.0 µm) 155 325 377 AHAM certifications

Pollen (5 – 11 µm) 155 370 378 KCl particle (0.1 – 1 µm) 163 308 197 KCl particle (0.523 – 3.162 µm)* 159 348 192 Our measurements

KCl particle (5.233 – 11.548 µm)* 184 454 225

Note: Diameter ranges marked with “ * ” are aerodynamic parameters.

Table 18 Comparisons with ASHRAE Rated MERV Values for In-duct Air Cleaners

Efficiency (%) Product D1 (MERV 15) Product D2 (MERV 9)

0.3 – 1.0 µm 85% ≤ E < 95% N/A

1.0 – 3.0 µm E ≥ 90% E < 50% Composite average particle size efficiency (ASHRAE 52.2) 3.0 – 10.0 µm E ≥ 90% E ≤ 85%

0.1 – 1.0 µm 86% 25% 0.523 – 1.0 µm* 84% 25% 1.0 – 3.162 µm* 85% 33%

Our measurements

3.162 – 10.0 µm* 74% 58% Note:

(1) Refer to ASHRAE 52.2-1999 for definition of MERV

(2) Diameter ranges marked with “ * ” are aerodynamic parameters

(3) For particles with diameter range of 3.162 – 10.0 µm, concentration decay was only measurable for 3.162 – 5.233 µm particles during the dynamic period

5. DISCUSSION

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5.1.3 Uncertainties

When determining CADR by regression of measured concentration decay according to Equation (5), results would be slightly different between fitting two parameters (C0 and ke) simultaneously and fitting only one parameter (ke) using the normalized concentration. Since fitting one parameter was generally more accurate and the characterization of air cleaner performance was only related with contaminant concentration decay, it was used to compute CADR in this project. Experimental results indicate that the current test and data analysis method worked well for portable air cleaners for which the airflow was provided by the air cleaner itself and typically less than 400 CFM. However, for in-duct air cleaners, larger airflow rates (i.e., 600 – 2000 CFM) were required and had to be provided by the system recirculating fan. This caused very rapid natural decay of large particles (i.e., 5.233 – 11.548 µm) before turning on the air cleaner and thus their removal by air cleaners could not be calculated. In addition, VOC concentration decay for products with good removal efficiency (such as D1) might be too fast to obtain an adequate number of valid sorbent tube samples (i.e. > 4) for accurate determination of CADR and its related uncertainty. A smaller recirculation flow rate (i.e. 200 – 400 CFM) would improve the resolution of the test method if a reliable model were available to extrapolate the performance measured at low flow rate to high flow rate(s) encountered in real applications. As discussed in Section 2.2.9, the uncertainty in CADR calculation was mainly related to the number of measurement data points and the degree of fit of the decay curves to the data points, so a larger number of data points would help to reduce the uncertainties. For example, uncertainties of CADRs for particles measured real-time with a 0.5 min sampling interval were generally smaller than those for VOCs from off-line tube sample analysis. Therefore, shortening the sampling interval or performing the test in a chamber with a larger volume (to slow down the concentration decay) would also improve the resolution of test method.

5.2 TECHNOLOGY AND PRODUCT EVALUATION

5.2.1 Quantification Of Ozone Emission From Electronic/Ionizer Air Cleaners

Figures 18 and 26 showed the increase of ozone concentration during the test of the electronic air cleaner (P3) and ionizer (P5). Assuming that the ozone removal mechanisms can be characterized by a first-order decay and the ozone generation rate of the air cleaner was a constant, the ozone emission rate can be estimated by fitting the measured concentration curve to the following equation based on the well-mixed single zone model:

)_1(_

_ todke

VodkoE

C⋅−

−⋅

= (8)

where,

E_o – ozone emission rate from the air cleaner, mg/h,

kd_o – the decay constant due to various removal mechanisms (i.e., surface deposition, chamber leakage rate), h-1.

Table 19 lists the estimated E_o and kd_o as well as the ozone concentration at the end of 6 hr test period. Figure 37 compares the measured concentrations and calculated results according to Equation (8) using

5. DISCUSSION

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53

the estimated E_o and kd_o. Results indicate that Equation (8) fitted the measurements well. The estimated decay constant was much larger in the P3 test than that in the P5 test. One possible reason is that the surface deposition rate of ozone during the P3 test could be larger than during the P5 test because P3 itself had a much higher flow rate than P5 (ionizer with no fan unit). The estimated ozone generation rate was 1.696 mg/h for P3 and 2.267 mg/h for P5, which were in the same order of magnitude as the ozone generation rates obtained for five ionizer air cleaners by Niu et. al (2001).

Table 19 Ozone Generation Rate and Maximum Concentration during Tests for Product P3 and P5

Device No. Estimated E_o (mg/h) Estimated kd_o (h-1) Ozone concentration at the end of 6 hr

test period (ppb)

P3 1.696 0.704 53

P5 2.267 0.188 175

0

50

100

150

200

0 1 2 3 4 5 6Time (hr)

Ozo

ne c

once

ntra

tion

(ppb

)

Measurement result for P5 Calculation result for P5Measurement result for P3 Calculation result for P3

Figure 37 Ozone concentration during testing of products P3 and P5: Measurement vs. Calculation

5.2.2 Removal of Particulates

Figure 38 shows the removal efficiency vs. particulate size for several particulate diameter ranges. Product P5 was not included as it had no fan unit and flow rate was not measured.

For portable cleaners using mechanical filtration (including charged media), all of the units claimed the use of a HEPA filter. The measured efficiencies ranged from around 50% to 80% for these products (P1, P2, P4 and P6) and the differences between removal efficiencies for different sizes of particles were small. By definition, a HEPA filter should have a minimum efficiency of 99.97% on 0.3 µm particles. However, none of tested products could approach that high efficiency. We postulated two possible reasons: 1) the products do not have a HEPA media as claimed, and/or 2) there were bypass flows (i.e. from gaps between HEPA filter and its holding frame). We could not verify the first reason without performing additional test on the HEPA media itself. However, product P2 did come with a certification

5. DISCUSSION

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showing that its HEPA filter had been independently tested according to European Norm (EN) 1822. To verify the second reason, we opened each product. Our observation confirmed that the HEPA filter and its holding frame were not perfectly tight. We then used a plastic sheet to fully cover (or wrap) the HEPA filter and measure the airflow rate again. If there was no bypass, there should be no or a very small airflow either at inlet or outlet. However, measurements showed that there were still significant amounts of airflow. For product P1, the measured flow was approximate 29% of normal operational airflow at the outlet and approximate 2% of normal operational airflow at the inlet, respectively. For product P2, the measured flow was approximate 7.4% of normal operational airflow and both were from inlet measurements. For product P4, the airflow rate was not measurable at the outlet. Certain leakage flows were observed at some edges for the units, but it was difficult to measure them accurately. For product P6, the measured flow was approximate 21% of normal operational airflow and both were from outlet measurements. Although these measurements did not reflect real operating conditions because the flow resistance might be much higher with the HEPA filter covered (wrapped), it was still a good indication that part of flow could bypass the filters during the operation. Therefore, the removal efficiency calculated here would be the overall system efficiency and not exactly the same as that calculated from a filter media test alone. For the portable air cleaner using electronic cells, its removal efficiencies were higher than other cleaners using HEPA filters and the removal efficiency for larger particles (> 3.162 µm) was larger than that for particles of smaller sizes. As for the two in-duct devices, the MERV 9 filter (produce D2) showed a clear increase of removal efficiency with the increase of particle sizes and the MERV 15 filter (product D1) showed similar removal efficiencies for particles over the measurable range of 0.1 – 5.233 µm.

0

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P1 P2 P3 P4 P6 D1 D2Product ID

Rem

oval

effi

cien

cy (%

)

0.1 - 1.0 um 0.523 - 3.162 um3.162 - 5.233 um 5.233 - 11.548 um

Figure 38 Measured removal efficiency vs. particle size

Only a limited number of products were tested as part of this project, so AHAM ratings for portable air cleaners were also investigated. There was no correlation between CADR and particle sizes which ranged from 0.1 – 1 µm (tobacco smoke), to 0.5 – 3.0 µm (fine dust) and 5 – 11 µm (pollen). Figure 39 summarizes the average CADR and Std (standard deviation)/Average CADR according to AHAM published data (AHAM 2005). Test results for portable air cleaners (not including the ionizer P5) from the current project are also shown in Figure 39. The average CADR (for tobacco smoke, fine dust and pollen) ranged from 38 to 392 for the 187 different air cleaner models tested by AHAM (no ionizers) and the Std /Average CADR was less than 10% for most of the tested air cleaners with an average CADR over 100. These results agreed with our measurements and indicated that the performance of most portable air cleaners was not very sensitive to particle size.

5. DISCUSSION

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0

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300

400

0 50 100 150 200Product ID

Ave

rage

CA

DR

(C

FM)

0

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30

40

Std/

Ave

. CA

DR

(%)

Average CADR - AHAM Publication Average CADR - Current ProjectStd/Ave. CADR - AHAM Publication Std/Ave. CADR - Current Project

Figure 39 Average CADR and Std/Ave. CADR for portable air cleaners

Table 20 compares the performance of tested air cleaners for particulate removal in terms of CADR, removal efficiency, watts/CADR, purchase $/CADR and ozone generation, respectively. There were no tests performed to determine the lifetime and long-term performance of the filter, so the filter replacement costs were not included in Table 20. For the portable air cleaners, the electronic air cleaner (P3) demonstrated the best performance. However, it generated a significant amount of ozone, although the ozone concentration at the end of test period (53 ppb) was approaching the steady state and still below the safety limit set by OSHA (80 ppb). For portable air cleaners using HEPA filters (P1, P2 and P6), their performances were generally in comparable ranges. For the portable air cleaner claiming the use of HEPA filter with enhanced method for charging particles (P4), its performance did not have obvious improvements compared to other air cleaners with HEPA filters only. For the ionizer (P5), its performance was poor though its power consumption was small. In addition, it generated a significant amount of ozone. The ozone concentration at the end of test period reached 175 ppb and was still increasing. It was difficult to compare the performance of in-duct air cleaners with portable ones using the CADR number because their CADRs were closely related to the testing flow rate. However, current tests still provided some useful information. For example, a MERV 15 in-duct filter could have equal or slightly better performance compared with portable air cleaners in terms of efficiency.

5. DISCUSSION

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Table 20 Comparisons of Tested Air Cleaners for Particulate Removal

Device No. Average CADR

Average removal efficiency (%) Watts/CADR Purchase $/CADR Ozone generation

P1 169 68 0.8 1.5 No P2 167 74 1.4 4.8 No P3 370 96 0.2 1.3 Yes (1.696 mg/h) P4 205 53 0.6 2.8 No P5 9 - 0.8 37.4 Yes (2.267 mg/h) P6 142 61 0.4 3.3 No D1 555 84 0 0.9 No D2 155 24 0.9 9.0 No

Notes:

(1) Average CADR and removal efficiency were the average for 0.1 – 1.0 µm, 0.523 – 3.162 µm and 5.233 – 11.548 µm particles for portable air cleaners and for 0.1 – 1.0 µm and 0.523 – 3.162 µm particles for in-duct air cleaners;

(2) For in-duct air cleaners, additional fan power requirement due to the pressure drop increase was not included. Power consumption of product P2 was due to the UV lamps for VOCs removal;

(3) Reported CADR for D1 and D2 were for a testing flow rate of 659 CFM and 667 CFM, respectively;

(4) Removal efficiency was not calculated for product P5 (ionizer) because its flow rate was not measured; (5) For column of ozone generation, values in “( )” were the estimated ozone generation rate based on the measured concentration increase during the 6 hr test period.

5.2.3 Removal of VOCs

Figure 40 shows the removal efficiency vs. vapor pressure for tested VOCs. Product P5 was not included since it had no significant removal effects for all the VOCs.

For most of sorbent-based air cleaners (P1, P2, P4, P6 and D1), their removal efficiencies for 6 of 8 injected VOCs with vapor pressure (VP) ranging from 1.25 to 151 mmHg (decane, iso-butanol, tetrachloroethylene, toluene, 2-butanone and hexane) could reach approximately 40% and higher. In addition, the relative differences between the removal efficiencies of these VOCs by the same product were small or insignificant. These products all had a significant amount of sorbent media, which was either in granular form (P2) or loaded (or impregnated) in other substrate materials (non-woven, fiber etc.) (P1, P4, P6 and D1). Several types of designs had been employed, including cylindrical (P1), flat panel (P4 and P6), pleated (D1) and V-shape cell (P2). As for product P3 that only had a very thin activated carbon post filter, it performed the worst, with a maximum efficiency of only 6%. In this case, the relative differences between removal efficiencies for different VOCs were significant. The heavier compound (lower vapor pressure) tended to have a greater efficiency in general (decane > tetrachloroethylene ≈ toluene > iso-butanol > hexane ≈ 2-butanone > dichloromethane ≈ formaldehyde). The performance of the sorption filters was determined by multiple factors (amount and properties of sorbent media, media packing density or binding technology, face velocity, etc.) and many of them were not known especially for portable air cleaners. It was difficult to correlate their performance with any single design parameter. As for the other two VOCs with higher vapor pressure (dichloromethane and formaldehyde), their removal characteristics were somehow different. The removal efficiency of dichloromethane (VP: 435 mmHg) was significantly lower than other compounds (not including

5. DISCUSSION

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formaldehyde) for all sorbent-based air cleaners except product D1. The removal efficiency of formaldehyde (VP: 3840 mmHg) varied from product to product (D1 > P2 ≈ P6 > P4 > P1 > P3) and had no obvious relationship with the removal efficiencies of other VOCs. In general, the air cleaners with more potassium permanganate media (D1 and P2) or individual formaldehyde filter (P6) had better removal efficiencies for formaldehyde.

Only one UV-PCO air cleaner (D2) was tested due to the lack of commercially available UV-PCO products. Its removal efficiency for the eight injected VOCs ranged from 1 to 15%. There were no obvious correlations between the removal efficiency and VOC vapor pressure. However, the removal efficiency tended to relate to the functional group of VOC species and followed the approximate order of oxygenated compounds (alcohol, ketone and aldehyde > aromatic and alkane hydrocarbon > halogenated aliphatic hydrocarbon). The same trend has been reported in some published studies (Chen et al. 2005, Hodgson et al. 2005, Lewandownski et al. 2002).

0

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Approximate Vapor Pressure at 25 oC (mmHg)

Rem

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P1 P2 P3 P4 P6 D1 D2

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Approximate Vapor Pressure at 25 oC (mmHg)

Rem

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)

P1 P2 P3 P4 P6 D1 D2

(a) (b)

Figure 40 Measured Removal Efficiency vs. VOC Vapor Pressure

Table 21 compares the performance of tested air cleaners for VOCs removal in terms of CADR, removal efficiency, watts/CADR, purchase $/CADR and ozone generation, respectively. There were no tests performed to determine the lifetime and long-term performance of the filters, so the filter replacement costs were not included in Table 21. The removal characteristics of decane, tetrachloroethylene, iso-butanol, 2-butanone and hexane were similar to that of toluene for most air cleaners tested (except for P3 and D2). Therefore, only the CADR and removal efficiency of toluene together with the average ± standard deviation of CADR and removal efficiency of these six VOCs are reported in Table 21. Detailed results for each VOC can be found in Appendix C. The removal characteristics of dichloromethane and formaldehyde were different. Therefore, they are listed separately in Table 21. Results indicate that sorption filtration was an effective technology in general. The in-duct air cleaner D1 had the largest amount of sorbent media and performed best. However, it should be noted that product D1 was actually advertised for commercial environments though the same technology could be used for residential applications. Its rated pressure drop of 0.46 in. w.g. at 500 fpm face velocity for the sorbent media filter might lead to significant system fan operating costs. For the portable air cleaners based on sorption technology, product P3 performed worst. The others had comparable performance in general and the ratings could be related to the specific VOC and performance criteria one would be interested in. For the UV-PCO technology, the only unit tested significantly removed most of the test VOCs but its performance could not compete with D1 in terms of initial efficiency and cost. As for the ionization

5. DISCUSSION

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products, the ionizer (P5) had no significant removal for any of the VOCs tested and generated significant amount of ozone.

Table 21 Comparisons of Tested Air Cleaners for VOCs Removal

Device No.

CADR (CFM) Removal efficiency (%)

Watts/CFM CADR Purchase $/CFM CADR

Ozone generation

Toluene

P1 138 (133 ± 8) 55 (53 ± 3) 1.0 1.8 No P2 95 (92 ± 7) 42 (40 ± 3) 2.5 8.4 No P3 7 (7 ± 8) 2 (2 ± 2) 9.6 71.3 Yes (1.696 mg/h) P4 216 (223 ± 20) 56 (58 ± 5) 0.6 2.6 No P5 0.1 (0.2 ± 0.1) - 72 3490 Yes (2.267 mg/h) P6 124 (116 ± 24) 54 (50 ±10) 0.4 3.8 No D1 588 (563 ± 52) 89 (85 ± 8) 0 0.9 No D2 40 (40 ± 33) 6 (6 ± 5) 3.6 35.0 No Formaldehyde P1 3 1 45.3 83 No P2 77 34 3.0 10.3 No P3 0.7 0.2 95.7 713 Yes (1.696 mg/h) P4 28 7 4.4 20.2 No P5 0.3 - 24 1163 Yes (2.267 mg/h) P6 77 33 0.7 6.1 No D1 440 67 0 1.2 No D2 45 7 3.2 31.1 No Dichloromethane P1 10 4 13.6 24.9 No P2 20 9 11.7 39.8 No P3 0.6 0.2 112 832 Yes (1.696 mg/h) P4 34 9 3.6 16.6 No P5 0.1 - 72 3490 Yes (2.267 mg/h) P6 8 4 6.4 58.8 No D1 502 76 0 1.0 No D2 4 1 35.5 350 No

Note:

(1) Reported CADR was equivalent average CADR number over test period (CADR_6h) defined in Equation 7 and reported removal efficiency was this average CADR number divided by the measured airflow rate through the air cleaner when the measured VOC concentrations could not directly fit the exponential decay;

(2) Since toluene was selected as the representative compound for 6 of 8 VOCs tested (toluene, iso-butanol, 2-butanone, hexane, decane and tetrachloroethylene), the average ± standard deviation of CADR and removal efficiency of these 6 VOCs were reported in “( )” following the CADR and removal efficiency of toluene. Detailed results for each VOC can be found in Appendix C.

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(3) Removal efficiency was not calculated for product P5 (ionizer) because its flow rate was not measured;


(5) For in-duct air cleaners, additional fan power requirement due to the pressure drop increase was not included;

(6) For column of ozone generation, values in “( )” were the estimated ozone generation rate based on the measured concentration increase during the 6 hr test period. The ozone generation of product P3 was due to the electronic cell for particulate removal.

5.3 EFFECTIVENESS OF TESTED AIR CLEANERS FOR IAQ CONTROL Concentrations of contaminants in indoor air result from the competition of various sources and removal processes. Air cleaning devices are often used in conjunction with source control and ventilation to reduce indoor contaminant concentrations. We developed a simplified model to demonstrate the potential effectiveness of tested air cleaners for achieving good IAQ to answer the following two questions:

How much additional percentage reduction of contaminant concentration can be obtained using the air cleaner?

If the air cleaner substitutes some mechanical ventilation to maintain a pre-defined acceptable concentration level, how much energy can be saved?

5.3.1 The Single-zone Model

Assuming a well-mixed condition, the contaminant (particle or VOC) mass (or number) balance can be presented as:

CacQacCnVQCSdtdCV ηλ −−−= (9a)

Or

CCADRCnVQCSdtdCV ⋅−−−= λ (9b)

where,

C = average indoor contaminant (particle or VOC) concentration

S = contaminant generation rate from various sources

Q = ventilation rate (including infiltration and outdoor air treated through the HVAC system)

V = volume of the house

λn = the removal rate due to removal processes other than air cleaning and ventilation

ηac = single-pass removal efficiency of the air cleaner

Qac = air flow rate through the air cleaner

CADR = clean air delivery rate of the air cleaner

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At steady-state conditions, Equation (9) has an analytical solution:

VCADRnVQVSC

///++

=λ

(10)

5.3.2 Effectiveness in Concentration Reduction

To estimate the reductions in indoor contaminant concentrations due to the use of air cleaners, the effectiveness (percentage reductions) was used with the reference case of no air cleaners. This parameter has been used to characterize the performance of air cleaners by other researchers (Fisk et al., 2002, Ward et al., 2003, Shaughnessy et al., 2005, Reed et al. 2002, Reed ea al. 2005):

VCADRnVQ

VCADR

refCacC

///1

++=−=

λε (11)

For particulates, the sources mainly include the indoor generated particles (tobacco smoke, dust-mite allergen, etc.) and the outdoor fine mode particles resulting from penetration to indoors, which all are size dependent. For VOC contaminants, the sources mainly include indoor emissions (building material, furniture, consumer products, etc.) and desorptions from building materials. The source strength may vary from house to house. However, as seen in Equation (11), the value of source strength (S) will not affect the calculation of ε, because it is percentage reduction in indoor contaminant concentration.

For particulates, removal other than ventilation and air cleaning (λn) is mainly due to surface deposition (λd). The surface deposition loss rate (λd) is the product of a mass transfer coefficient called the deposition velocity and the ratio of indoor surface area (As) to volume (V). It depends on particle size and can vary by almost three orders of magnitude in the size range of 0.1 – 10 µm (Fisk et al, 2002, Shaughnessy et al., 2005). Shaughnessy et al. (2005) used a deposition removal rate of approximate 0.05 h-1, 1 h-1 and 10 h-1 for small-sized particles less than 0.8 µm (e.g. tobacco smoke), medium-sized particles of 1 - 4 µm (e.g. house dust, cat allergen) and large-sized particles of 6 – 20 µm (e.g. pollen), respectively.

For VOC contaminants, removal mechanisms other than ventilation and air cleaning (λn) include mainly adsorption by building materials (sink effect) and possible indoor reactions. These effects are related to the characteristics of VOC species.

Our model is based on the following assumptions:

Our base home is a 2,300 ft2 single-family residence with a volume of 513 m3 based on a ceiling height of 2.4 m

The removal rate by surface deposition for particles is 0.05 h-1, 1 h-1 and 10 h-1 for particles in the size range of 0.1 –1 µm, 0.523 – 3.162 µm, and 5.233 – 11.548 µm respectively.

The removal of VOC contaminants by mechanisms other than ventilation and air cleaning is negligible.

Three reference cases (without an air cleaner), representing different levels of air tightness in current building practice, were defined:

A high total air exchange rate of 0.5 ACH.

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A moderate total air exchange rate of 0.35 ACH.

A low total air exchange rate of 0.1 ACH.

The percentage reduction was then calculated using the range of CADRs (efficiencies) obtained from the current study, assuming that the air cleaner is regularly serviced (i.e. replacing the filter media periodically) and maintains its initial performance. For particulates, results were reported for three particle size ranges approximately corresponding to the size range of tobacco smoke, fine dust and pollen, respectively. For VOCs, toluene was used as the representative of VOCs with vapor pressure smaller than 151 mmHg. Results were calculated and reported for toluene, dichloromethane and formaldehyde. Figures 41, 42 and 43 show the calculated reductions in indoor concentration of pollutants for the base-cases of 0.5, 0.35 and 0.1 ACH, respectively.

Calculations were performed for the use of one or two portable air cleaners with highest, median and lowest CADRs, and for the use of the in-duct air cleaners. For portable air cleaners, product P5 was not included as the tests indicate that it had very modest or insignificant removal capability. For in-duct air cleaners, a flow rate of 800 CFM, which was close to the testing flow rate, was used and the removal efficiencies were assumed to be the same as those obtained from the tests.

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0

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Size range of particles

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1 portable AC (lowest)1 portable AC (median)2 portable AC (highest) 2 portable AC (lowest)2 portable AC (median)in-duct, MERV 15, 800 CFMin-duct, MERV 9, 800 CFM

(a) Particles

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Toluene Dichloromethane Formaldehyde

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1 portable AC (median)




in-duct, 12 lb sorbent media, 800CFMin-duct, UV-PCO, 800 CFM

(b) VOCs

Figure 41 Calculated percentage reductions in concentration for the base-case of 0.5 ACH of total air exchange

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0

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0.1 – 1µm 0.523 – 3.162 µm 5.233 – 11.548 µm


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in-duct, 12 lb sorbentmedia, 800 CFMin-duct, UV-PCO, 800CFM

(b) VOCs

Figure 42 Calculated percentage reductions in concentration for base-case of 0.35 ACH total air exchange

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0

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0.1 – 1µm 0.523 – 3.162 µm 5.233 – 11.548 µm


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in-duct, 12 lb sorbent media, 800CFMin-duct, UV-PCO, 800 CFM

(b) VOCs

Figure 43 Calculated percentage reductions in concentration for base-case of 0.1 ACH total air exchange

Results indicated that the overall effectiveness of air cleaners becomes more significant with reduced air exchange rates. For example, the percentage reduction by using one portable air cleaner with highest CADR increased from 46% at 0.5ACH to 81% at 0.1ACH for toluene.

As discussed in Section 3.5.2, the measured CADRs only showed a minor sensitivity with regard to particle size. However, the percentage reduction (effectiveness) for particle removal due to the use of air cleaner(s) was very much dependent on particle size and decreased significantly as the particle size increased because the natural decay rate for larger particles were larger. For example, use of one portable air cleaner could provide approximate 37 – 52% reduction at 0.5ACH for particles in the size range of 0.1 – 1.0 µm and the percentage reduction was only 3 – 8% for particles in the size range of 5.233 – 11.548 µm. Using two portable air cleaners could increase the overall percentage reductions. However, the calculated reductions were still less than 15% for large particles, suggesting that use of air cleaners only

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had modest effects on control of large-sized particles (e.g. pollen and dust mite). As for the effectiveness of in-duct devices, results indicate that the MERV 15 filter could provide a percentage reduction similar to the use of two portable air cleaners with highest CADR and the MERV 9 filter could reach a percentage reduction comparable to the use of one portable air cleaner with median CADR.

As for VOCs, results show that the effectiveness of an air cleaner might be different for toluene, dichloromethane and formaldehyde. For example, use of one portable air cleaner at 0.5ACH could provide a maximum reduction of 46% for toluene concentration but only 23% and 12% for formaldehyde and dichloromethane, respectively. As for the in-duct devices, the sorption filter using 12 lb sorbent media provided largest percentage reduction for all of the VOCs. The UV-PCO device had a percentage reduction generally comparable to the portable air cleaner with median CADR number.

Having the range of CADRs obtained from this project, the absolute concentrations achievable by the combined use of source control, ventilation and air cleaners for any house can be calculated from Equation (9) when more detailed information (source strength and characteristics, ventilation schedule, etc.) is provided.

5.3.3 Energy Savings and Cost Benefit

The above discussions are mainly from the contaminant control point of view. When selecting the whole-house IAQ control strategy, one must also consider the associated energy and total costs. The use of air cleaners to decrease the outdoor air intake reduces the ventilation-related energy costs (energy use due to the heating or cooling of the outdoor air and the energy use imposed by fan operations) but results in additional costs no matter which system is chosen. The total costs of an in-duct air cleaner mainly include the purchase cost, replacement cost (filter, catalyst insert etc.), the incremental costs of energy used by fans, and energy costs due to its own power consumption (for UV-PCO or electronic type). The total costs of a portable air cleaner mainly include the purchase cost, replacement cost (e.g. filter), and energy cost due to its own power consumption.

An analysis was performed to compare the energy cost between ventilation and use of a portable air cleaner using the simple steady-state model. Two cities, Syracuse, NY and Chicago, IL, were selected for analysis. Since mechanical ventilation is typically not necessary when the home has an infiltration rate of 0.35 ACH and above, the energy savings due to the use of air cleaner was calculated for the following reference case only:

A single-family home of 2,300 ft2 (volume of 513 m3 assuming a ceiling height of 2.4 m)

The house has a total air exchange rate of 0.35 ACH, of which 0.15 ACH is due to infiltration and 0.2 ACH due to mechanical ventilation.

When using an air cleaner, it was assumed that there was no mechanical ventilation and that the air cleaner reduced the contaminant concentrations equivalent to 0.2 ACH of mechanical ventilation. Based on the results provided in Tables 20 and 21, the most energy efficient of the tested products (smallest watts/[CFM pollutant free flow]) were used in the model. Only ventilation-related or air cleaner-related energy consumptions (gain) were considered. The following assumptions and conditions were used in the calculation:

A well-mixed condition was assumed.

An exhaust-only ventilation system was assumed. The energy used to heat or cool outdoor air was only dependent on the air mass flow rate and the indoor-outdoor enthalpy difference.

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The exhaust fan power was typically within the range of 0.5 to 1 watts/cfm (i.e. 0.6 watts/cfm reported by Wray et al., 2000). The mechanical ventilation-related fan power consumption in calculations was estimated at 0.5 watts/cfm.

The air cleaner was operating continuously for the whole year (24/7/365) and 100% of the heat was released indoors;

The efficiency of the furnace was assumed to be 0.8, the EER of the air conditioning system was assumed at 10 and the efficiency of the water heater was assumed to be 0.6. These values correspond to the Building America 2005 Benchmark;

Heating set point of 71 oF (and humidification set point of 40%RH or 45 gr/lb) with heating (and humidification) operational below 66 oF ambient for the base case assuming 5F temperature rise from internal gains.

Cooling set point of 76 oF (and dehumidification “set point” of 50%RH or 67 gr/lb) with cooling (and dehumidification) operational above 71 oF ambient for the base case assuming 5 oF temperature rise from internal gains.

The TMY2 8760 hour weather data were used.

Energy prices for Chicago: $0.08275/kWh (electricity), $1.0026 for first 20 therms, $ 0.913 for the next 30 therms, and $0.9096 for over 50 therms (natural gas).

Energy price for Syracuse: $0.11589/kWh (electricity), $14.71 for basic service charge (first 3 therms), $ 0.34921 for next 47 therms, and $0.05322 for over 50 therms (natural gas). Because the basic service charge could not be saved in any case due to the other heating and hot water usage, it was not included in the calculation.

Calculation results are summarized in Table 22 and Table 23 for Syracuse and Chicago, respectively. The energy consumption of the air cleaner for removal of particulates, toluene or formaldehyde was less than 15% of lighting and other appliances (approximate 3000 kWh for lighting and a refrigerator for a 2,300 ft2 home), the HVAC benefit (or penalty) due to the heat release of air cleaner was neglected. For dichloromethane, the heat release of the air cleaner for providing 0.2 ACH equivalent clean air exchange rate was approximately 60% of lighting and other appliances (approximate 3,000 kWh for lighting and a refrigerator for a 2,300 ft2 home) due to the low removal efficiency, and the HVAC benefit (or penalty) was accounted by considering an additional 3F temperature rise from internal gains. Detailed calculation sheets can be found in Appendix D.

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Table 22 Energy Cost Comparison Based on Steady-State Model for Syracuse, NY

0.2 ACH equivalent clean air provided by a portable air cleaner (based on most efficient product tested)

Base case with 0.2 ACH mechanical ventilation Particulates Toluene Formaldehyde Dichloromethane

Annual electricity (kWh) 403

Annual natural gas (therms) 219

Annual energy cost ($) $72.30 Annual electricity by air cleaner (kWh) 106 212 370 1904

Annual operation cost of air cleaner ($) $12.30 $24.50 $42.90 $220.60

HVAC benefit (or penalty) due to the heat release of air cleaner ($)

Neglected Neglected Neglected -$2.80

Annual cost savings compared to base case ($)

$60.00 $47.70 $29.40 -$151.20

Note: Negative numbers mean that the use of air cleaner cost more compared to the base case.

Table 23 Energy Cost Comparison Based on Steady-State Model for Chicago, IL

0.2 ACH equivalent clean air provided by a portable air cleaner (based on most efficient product tested)

Base case with 0.2 ACH mechanical ventilation Particulates Toluene Formaldehyde Dichloromethane

Annual electricity (kWh) 455

Annual natural gas (therms) 206

Annual energy cost ($) $226.50 Annual electricity by air cleaner (kWh) 106 212 370 1904

Annual operation cost of air cleaner ($) $8.80 $17.50 $30.60 $157.50

HVAC benefit (or penalty) due to the heat release of air cleaner ($)

Neglected Neglected Neglected $6.90

Annual cost savings compared to base case ($)

$217.80 $209.00 $195.90 $75.90

Note: Negative numbers mean that the use of air cleaner cost more compared to the base case.

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Results indicate that there are significant savings using the best available air cleaner to replace the mechanical ventilation if particulates, toluene (or VOCs with vapor pressure smaller than 150 mmHg) or formaldehyde were the target pollutants. However, even the best portable air cleaner tested costs more than mechanical ventilation to provide the same clean air exchange rate for dichloromethane due to the low removal efficiency. In general, an air cleaner would need to perform better than $1.2/CADR (in Syracuse) or $3.75/CADR (in Chicago) for a target pollutant to obtain the energy cost benefit compared with mechanical ventilation. For particulates, five of six portable air cleaners tested performed better than this cut-off value (e.g. $1.2/CADR for Syracuse condition). For VOCs, three of six products tested performed better than this cut-off value for toluene and only one product performed better than this cut-off value for formaldehyde, suggesting that well designed portable air cleaners could bring energy cost benefit compared with mechanical ventilation for general VOC control purpose.

More comprehensive cost comparisons between ventilation, in-duct and portable air cleaners require more detailed information such as building envelope structure, air cleaner operation and maintenance schedule, and thus need further investigations in the future.

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6. CONCLUSIONS 6.1 AIR CLEANER PERFORMANCE Eight air cleaning devices have been tested in a full-scale stainless steel chamber using a “pull-down” test method with simultaneous injection of potassium chloride (KCl) particles ranging in diameter from approximate 0.10 to11µm and a mixture of eight representative VOCs. Their initial effectiveness was evaluated in terms of CADR and system removal efficiency. Other important parameters, including ozone emission, power consumption, noise level, and pressure drop across in-duct devices, were also measured. The tested products employ different technologies for gas-phase contaminants and particulates removal, including sorption, filtration (some with charged media or pre-charged particles), UV-photocatalytic oxidation (UV-PCO), electronic precipitator and air ionization. The effectiveness and potential energy benefits of using the tested air cleaning devices were also briefly discussed.

The major findings are:

Mechanical filtration and electronic precipitator are two effective methods to remove indoor particulate contaminants as demonstrated by the commercial products tested. However, the latter method has the potential of generating significant amount of ozone. The portable electronic air cleaner tested had better performance (in terms of CADR, removal efficiency and cost) than other portable air cleaners claiming the use of HEPA filters, but generated significant amount of ozone. As for the ionization, the ionizing product without a fan unit, though quiet, only had very modest removal capacity for particulates and generated very significant amount of ozone.

None of the four portable air cleaners claiming the use of HEPA filters (product P1, P2, P4 and P6) could approach a removal efficiency of ≥ 99.97%. The measured efficiencies ranged from around 50% to 80% for these products and the difference between removal efficiencies for different size of particles were relatively small. This relative insensitivity of removal efficiency to particle sizes for portable air cleaners were further verified by comparing the test results to published AHAM certified CADRs, where a larger number of products (187) were tested. Visual observations and a quick investigation of flow rate measurement with the filter covered (or wrapped) by a plastic sheet indicated that the HEPA filter and its holding frame (or product frame) were not perfectly tight and there was some bypass airflow. Therefore, the removal efficiency calculated here was not exactly the same as that obtained from HEPA media-only test and should be considered as the overall system efficiency for portable air cleaners.

Sorption and UV-photocatalytic oxidation are two effective methods to remove indoor VOC contaminants, although most of off-the-shelf products are based on sorption technology. Only one UV-PCO in-duct air cleaner was tested and its performance, in terms of initial removal efficiency and cost, could not compete with the in-duct filter with approximately 12 lb sorbent media. However, since PCO-based products have negligible pressure drop (with a honeycomb monolith modular design), good long-term performance and “true” theoretical removal of contaminants (converting to CO2 and water), it is still a viable and promising approach. As for the ionization, the ionizer without fan unit had no significant removal effect for all the VOCs tested and generated a significant amount of ozone.

The removal efficiency of a specific VOC is related to its properties. For sorption technology, a heavier and low-volatility compound is generally expected to have a higher absorbability on activated carbon than a lighter and more volatile compound. Product P3 that only had a very thin activated carbon post-filter and a maximum efficiency of 6% followed this trend. For other products which had significant amount of sorbent media that was either in granular form (P2) or

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loaded (or impregnated) in other substrate materials (non-woven, fiber etc.) (P1, P4, P6 and D1), the removal efficiencies for 6 of 8 injected VOCs with vapor pressures (VP) ranging from 1.25 to 151 mmHg (decane, iso-butanol, tetrachloroethylene, toluene, 2-butanone and hexane) were close and reached approximately 40% or higher. Only the removal efficiency for dichloromethane (VP: 435 mmHg) was significantly lower. The removal efficiency for formaldehyde (VP: 3840 mmHg) of products with activated carbon only was low. The removal efficiency increased when potassium permanganate media was used. For UV-PCO technology, the removal efficiency was found to be more closely related to the functional group of chemicals. For the VOCs tested, the oxygenated compounds (alcohols, ketones, aldehydes) had higher removal efficiencies, followed by the aromatic and alkanes. The lowest removal efficiencies were observed for the two chlorocarbons (dichloromethane and tetrachloroethylene).

The proposed test method worked well for portable air cleaners for which the airflow is provided by the air cleaner itself and is typically less than 400 CFM. No significant difference was observed for particulate removal between tests with particle injection only and with simultaneous injection of particles and VOCs. For in-duct air cleaners tested under rated operating airflow rates (i.e. 600 – 2000 CFM), accurate determination of CADR was difficult for large size particles (>5 um) due to rapid natural decay. The same was true for VOCs if the air cleaner had relatively high removal efficiency. A smaller recirculation flow rate (i.e. 200 – 400 CFM) might improve the resolution of the test method if a reliable model were available to extrapolate the performance measured at a low airflow rate to high airflow rate(s) encountered in real world applications. Developing the extrapolation model and a model-based test procedure for performance evaluation is hence an important subject for further research.

Although the measured CADRs only showed a minor sensitivity to particle size for portable air cleaners, the effectiveness (percentage reduction) of particle removal due to the use of air cleaner(s) was very dependent on particle size. It decreased significantly as the particle size increased because the natural decay rate for larger particles was larger. As for the VOCs, the effectiveness differed from compound to compound. The overall effectiveness (percentage reduction) of air cleaners becomes more significant when the overall air exchange rate, i.e., the sum of infiltration and mechanical ventilation, is low. Using a steady state model, the potential energy savings of an air cleaning approach to a mechanical ventilation-only approach were evaluated. It was found that use of air cleaners may result in energy savings when compared to a dilution by ventilation approach. For example, five of six portable air cleaners tested saved energy for particle removal for the reference case defined in this study. This was true for only a few of the tested products for removal of VOCs.

6.2. SYSTEM DESIGN CONSIDERATIONS The test results obtained from this project were based on the overall initial performance of air cleaners. They provided some information with regard to potential product improvements.

For sorption filtration, the following design strategies may be considered:

1. Sorbent media selection

The activated carbon was effective for a wide range of VOC contaminants (except highly volatile compounds such as formaldehyde and dichloromethane).

Potassium permanganate was more effective in removing formaldehyde than activated carbon.

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2. Filter media and assembly design

Only a thin activated carbon (impregnated) pre- or post-filter in portable air cleaner (P3) is insufficient to achieve significant removal of VOCs.

The sorbent-loaded non-woven with 12 lb of blended media in pleated form (P1) performed best.

The removal efficiencies of most of VOCs were similar for tested air cleaners with cylindrical design (P1), flat panels (P4 and P6) and V-bank (P2). However, different amounts and types of activated carbon have most likely been used in these products. Research on different filter designs with the same media is needed to draw further conclusions. A design model accounting for geometry and airflow movement as well as sorbent media performance is needed to optimize the air cleaner performance.

Larger amount of sorbent media (P2 >> P6), though possibly having a longer lifetime, did not result in a better initial performance.

For mechanical filtration (including charged media/pre-charged particles), the air cleaner with pre-charged particles and HEPA filter (P4) did not show significant improvement compared to air cleaners with only a HEPA filter.

By-pass airflows were observed between the filters and their holding frame for many of the portable air cleaners tested. Since the performance of the air cleaning device is determined by its overall efficiency, efforts to reduce any possible by-pass airflows may be warranted.

For electronic air cleaners, ozone generation is a concern and needs to be evaluated.

Test results indicate that the rankings of the air cleaners according to their respective removal efficiency expressed as CADR and energy efficiency of the removal process expressed as watts/CADR can be different. Future air cleaner designs may want to optimize the system for both of these parameters.

6.3 AIR CLEANER INSTALLATION CONSIDERATIONS The primary objective of this project was to evaluate the performance of air cleaners in standard laboratory test conditions rather than in a real building subject to various installation and operation conditions. To extrapolate the chamber test results to real house conditions, two questions have to be answered:

How will different installation conditions influence the performance of air cleaner?

How will different operating conditions influence the performance of air cleaner?

For in-duct air cleaners, the installation conditions mainly refer to the significance of gaps (between filter media and its frame and between the frame and duct) and bypass flow. Current chamber test results show that the use of an in-duct filter with 12 lb blended sorbent media and MERV 15 media under 800 CFM had pollutant percentage reductions better than the use of 2 portable air cleaners with highest performance. However, these tests were performed in well-sealed conditions (avoiding by-pass flow as much as possible). In reality, sizable gaps are common and the amount of by-pass flow will be influenced by the quality of air cleaner installation by HVAC contractors. The overall efficiency will be determined by the size of the gap, the filter efficiency rating under lab test conditions and the pressure drop over the filter. Sometimes, the amount of bypass flow can be large and result in an overall performance significantly lower than that measured in lab conditions. Ward et al. (2005) has developed a model to quantify the amount of air that bypasses the filter and its effect on the overall filter efficiency. They

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found that the bypass was significantly detrimental to indoor air quality because respirable particles were not appreciably removed in the gap. For example, the performance of a MERV 15 filter with large gap (10 mm) only equaled a MERV 8 filter with no gap. However, not enough experimental data were provided in this paper. Further research should be conducted to obtain laboratory experimental data with controlled parameters (well-characterized gap geometry and size, face velocity etc.) to validate the model.

For portable air cleaners, the installation conditions mainly refer to the room location of the air cleaner (corner, center, wall mounted, above desk etc.). The filter bypass may also occur in portable air cleaners, but its effect has been included in the measured overall efficiency from chamber test results. Since the contaminants have to enter into the air cleaner first to be removed, the air cleaner should be located near the point contaminant sources and without obstructions to air flow. If the contaminant sources are assumed to be evenly distributed and the air is well mixed inside the room, the measured average room concentration should be the same. Reed et al. (2005) tested the performance of a portable air cleaner at two different locations (center and corner of the room) using decane as the challenge contaminant. They found that in general the difference in removal efficiency was relatively small, but the regression analysis did show that the location had a significant effect on air cleaner performance. When the air cleaner was located in the center of the room, the removal efficiency was 2% less than when the air cleaner was located in the corner of the room.

For in-duct air cleaners, the operating conditions mainly include the airflow rate, cycling conditions of HVAC system, temperature and relative humidity. For portable air cleaners, the operating conditions mainly include the setting of operating level (airflow rate), temperature and relative humidity. It should be noted that the influence of operating conditions on the performance of air cleaners might be different for different technologies. Some field tests have been performed in research houses to investigate the influence of these conditions on the performance of air cleaners (Emmerich et al. 2001, Reed et al. 2005). A model which extrapolates the performance of air cleaners under controlled lab conditions (i.e. data obtained from this project) to different operating conditions needs to be developed and validated by experimental data.

6. REFERENCES

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6. REFERENCES ANSI/AHAM Standard AC-1-2002. Method for Measuring Performance of Portable Household Electric Cord-connected Room Air Cleaners. Association of Home Appliance Manufacturers.

ANSI S12.10-2002. Acoustics – Measurement of airborne noise emitted by information technology and telecommunications equipment. The American National Standards Institute, Inc.

AHAM 2005. 2005 Directory of Certified Room Air Cleaners, edition No.1, Association of Home Appliance Manufacturers.

ASHRAE Standard 52.2-1999. Method of Testing General Ventilation Air-cleaning Devices for Removal Efficiency by Particle Size. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

ASHRAE Std. 145.1P, 2005. Laboratory Test Method of Assessing the Performance of Gas-Phase Air Cleaning Media (draft). Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

ASTM standard D6670-01, 2001. Standard practice for full-scale chamber determination of volatile organic emissions from indoor materials/products. American Society for Testing and Materials.

Chen W, Zhang JS, and Zhang Z, 2005. Performance of air cleaners for removing multiple volatile organic compounds in indoor air. ASHRAE Transactions, 111 (1), p1101-1114.

Daisey JM and Hodgson AT, 1989. Initial efficiencies of air cleaners for the removal of nitrogen dioxide and volatile organic compounds. Atmospheric Environment, Vol. 23, No.9, p1885 – 1892.

Emmerich SJ and Nabinger SJ. 2001. Measurement and simulation of the IAQ impact of particle air cleaners in a single-zone building. Report No.: NISTIR 7114. National Institute of Standards and Technology (NIST).

EPA. 2000. Ozone generators that are sold as air cleaners: an assessment of effectiveness and health consequences. Available online: http://www.epa.gov/iaq /pubs/ozonegen.html. U.S. Environmental Protection Agency.

EPA. Residential Air Cleaning Devices: A Summary of Available Information. Available online: http://www.epa.gov/iaq /pubs/residair.html. U.S. Environmental Protection Agency.

Fisk WJ, Faulkner D, Palonen J and Seppanen O, 2002. Performance and costs of particle air filtration technologies. Indoor Air (12), p223 – 234.

Godish Thad. 2001. Indoor Environmental Quality. Lewis Publishers.

Hanley JT, Ensor DS, Smith DD and Sparks LE, 1994. Fractional aerosol filtration efficiency of in-duct ventilation air cleaners. Indoor Air (4), p169 – 178.

Hanley JT, Smith DD and Ensor DS, 1994. A factional aerosol filtration efficiency test method for ventilation air cleaners. ASHRAE Transactions, p97 – 110.

Herrmann TJ, Zhang JS, Zhang Z, Smith J, Gao X, Li H, Chen W and Wang S, 2003. Performance Test Results for an Innovative Large Coupled Indoor/Outdoor Environmental Simulator (C-I/O-ES). ASHRAE Transaction, 109 (2), p503 – 516.

http://www.epa.gov/iaq /pubs/ozonegen.html

http://www.epa.gov/iaq /pubs/residair.html

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Hodgson AT and Levin H, 2003. Volatile organic compounds in indoor air – a review of concentrations measured in North America since 1990. Report No.: LBNL-51715. Lawrence Berkeley National Laboratory.

Hodgson AT, Sullivan DP and Fisk WJ, 2005. Evaluation of ultra-violet photocatalytic oxidation (UVPCO) for indoor air applications: conversion of volatile organic compounds at low part-per-billion concentrations. Report No. LBNL-58936. Lawrence Berkeley National Laboratory.

Lewandowski M and Ollis DF, 2002. Photocatalytic Oxidation of Gas-Phase Aromatic Contaminants. in Semiconductor Photochemistry, V.Ramamurthy and K. F. Schanze (eds), vol 9 of Molecular and Supramolecular Photochemistry, Marcel Dekker, New York.

Nazaroff WW, 2000. Effectiveness of air cleaning technologies. Proceedings of Healthy Building 2000, Vol. 2, p49 – 54.

Niu J, Tung TCW, and Chui VWY, 1998. Using large environmental chamber technique for gaseous contaminants removal equipment test. ASHRAE Transaction, 104 (2), p 1289 – 1996.

Niu J, Tung TCW, and Burnett J, 2001. Quantification of dust removal and ozone emission of ionizer air cleaners by chamber testing. Journal of Electrostatics, 51-52, p 20-24.

Offermann, FJ, Sextro RG, Fisk WJ, Grimsrud DT, Nazaroff WW, 1985. Control of respirable particles in indoor air with portable air cleaners. Atmospheric Environment, Vol. 19, No.11, p1761-1771.

Reed CH, Nabinger SJ, and Emmerich SJ, 2002. Measurement and simulation of the indoor air quality impact of gaseous air cleaners in a test house. Proceedings of Indoor Air 2002, p652 – 657.

Reed CH, Nabinger SJ, and Emmerich SJ, 2005. Predicting gaseous air cleaner performance in the field. Proceedings of Indoor Air 2005, p652 – 657.

Shaughnessy R and Sextro R, 2005. What is considered an “effective” air cleaning device? Proceedings of Indoor Air 2005, p2970 – 2975.

VanOsdell DW, 1994. Evaluation of test methods for determining the effectiveness and capacity of gas-phase air filtration equipment for indoor air applications – Phase I: Literature review and test recommendations. ASHRAE Transactions, 100 (2), p511- 523.

Ward M, Siegel JA and Corsi RL, 2003. Stand alone air cleaners: Evaluation and implications. Proceedings of Engineering Solutions in Indoor Air 2003.

Ward M and Siegel JA, 2005. Modeling filter bypass: impact on filter efficiency. ASHRAE Transactions, 111(1), p1091-1100.

Weschler CJ, 2000. Ozone in indoor environments: concentration and chemistry. Indoor Air(10), p269 – 288.

Wainman T, Zhang J, Weschler CJ, and Lioy PJ, 2000. Ozone and limonene in indoor air: a source of submicron particle exposure. Environmental Health Perspectives 108(12), p1139 – 1145.

Wray CP, Matson NE and Sherman MH, 2000. Selecting whole-house ventilation strategies to meet proposed ASHRAE standard 62.2: energy cost considerations. LBNL Report, Report No. LBNL-44479. Lawrence Berkeley National Laboratory.

APPENDIX A: DETAILED SPECIFICATIONS OF SELECTED AIR CLEANERS

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APPENDIX A: DETAILED SPECIFICATIONS OF SELECTED AIR CLEANERS

Type of air cleaning technologies (Stated by manufacturer) Device

No. Particulate VOCs

Recommend room size Note

Portable Air Cleaners

P1 99.97% HEPA filter with average life of 1 – 3 years

(1) Activated carbon pre-filter. Recommend replacing filter every 3 months. (2) Gas and odor adsorption filter (sorbent mixture blends charcoal, potassium permanganate and zeolite). Recommend replacing filter every 6 months.

252 sq ft (1) Three operation levels (2) CADR certified by AHAM.

P2 (1) Pre-Filter with average life of 6 – 18 months (55% efficiency at 0.3 microns, >90% efficiency at 5 microns, 25 ft area) 2

(2) HEPA filter with average life of 2 – 4 years. (Cleanroom H12/H13 grade filter, 99.97% DOP media, mini-pleat with solvent free separators, 40 ft2 area)

Gas and odor adsorption filter with average life of 1-2 years (5 V-shaped gas filter pockets containing 5 pound blend of granular activated carbon and potassium permanganate impregnated alumina)

Maximum 900 sq ft (based on maximum fan speed and an 8.5 ft ceiling)

(1) Six operation levels (2) No certified CADR from AHAM.

P3 (1) Pre-filter for larger particles (2) Electrostatic precipitator (Electronic cell + Collector plates)

Activated carbon post filter. Recommend replacing filter every 6 months.

465 sq. ft. (1) Three operation levels (2) CADR certified by AHAM.

P4 Two-stage HEPA technology (combination of mechanical and active electrostatic filtration methods): Particles are negatively charged before reaching the HEPA filters. Recommend replacing filters every 6 months.

Enhanced active carbon filter for gas adsorption. Recommend replacing filters every 6 months.

Up to 620 sq. ft.

(1) Four operation levels (2) CADR certified by AHAM.

P5 Electronic ionization (use of an electrical charge to create air that is densely packed with positively charged ions and negatively charged electrons) and collection blades

Electronic ionization (advertised for reducing common odors, but not specifically advertised for VOCs)

500 sq ft (1) Three operation levels but no fan unit (2) No certified CADR from AHAM.

P6 (1) Metallic pre-filter (permanent use with water cleaning every month) (2) HEPA filter. Recommend replacing filter every 2 – 3 years

Combination of an allergen filter, a formaldehyde filter and a VOCs filter. Recommend replacing filters every 2 – 3 years.

366 sq ft. (1) Four operation levels (2) No certified CADR from AHAM.

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Type of air cleaning technologies (Stated by manufacturer) Device

No. Particulate VOCs

Recommend room size Note

In-Duct Air Cleaners

D1 An integral particulate filter media having a MERV rating of 15 in the pleated form

An adsorbent-loaded non-woven containing combination (50:50 by volume) of potassium permanganate granular media and activated carbon granular media (total approximate 12 lb)

Whole house (multi-rooms)

Advertised for commercial environments (hotels, office buildings, etc.)

D2 A pleated, 4” MERV 9 filter Six 17 watt UVA lamps and a honeycomb catalyst coated insert

Whole house (multi-rooms)

Advertised for residential applications

APPENDIX B: “PULL-DOWN” TEST PROCEDURE

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Air Cleaner Performance Test Procedure “Pull-Down” Test

SYRACUSE UNIVERSITY

BEESL LAB

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1. PURPOSE This test procedure is used to assess the initial performance of room air cleaners for removing volatile organic compounds (VOCs) and aerosol particles under standard test conditions by the “pull-down” chamber test method. The objectives of the test are as follows:

(1) Characterize the effects of test environmental chamber on the test results. (2) Examine the performance of air cleaner under simultaneous release of VOC and particulate

contaminants. More specifically, obtain the decay of concentration vs. time for each test VOC and different size particles due to the application of the tested air cleaner.

(3) Monitor the possible by-products generation from the tested air cleaner (e.g., ozone and VOCs that are different from the injected compounds).

(4) Quantify the performance of the tested air cleaner using the concept of clean air delivery rate (CADR), and obtain the removal efficiency for each test VOC and different size particles by the data analysis procedure based on a well-mixed single zone IAQ model.

2. RESPONSIBILITIES

(1) Test Performers - Wenhao Chen and Zhi Gao, Graduate Research Assistants: Have overall responsibility for conducting test and perform data analyses.

(2) Chemist – Dr. Zhibin Zhang, Research Scientist: Provides consulting and quality control for chemical compound preparation, sampling and analysis method.

(3) HVAC Engineer – Mr. James Smith, Research Design Engineer: Provides consulting and quality control for the operation and maintenance of the chamber system.

(4) Principle Investigator – Dr. Jensen Zhang: Assumes overall responsibility for the scientific integrity of the study, reviews and approves test procedures, re-enforces expectations for the test, and provides university management oversight of the test.

3. PRECAUTIONS AND LIMITATIONS

(1) Any action, response, or condition that is observed or perceived as abnormal, or out of tolerance,

shall be promptly evaluated for its impact on the continuation of the test. (2) The test performer may take necessary immediate steps to secure equipment if necessary. Testing

shall then be halted and the steps taken prior to resuming the testing. Events should be documented in the Procedure Log.

(3) Standard safety practices shall be observed at all times (i.e. use of eye protection, etc.). (4) Refer to BEESL General Facility Manual for Instructions and Operation Procedures for each

instrument. (5) If a temporary change to this procedure resulting from an exception is needed, the initiator of the

change shall review the design specification prior to implementing the procedure change. The review will ensure that the change does not conflict with any portion of the design and therefore will not result in any unacceptable deviations.

(6) Steps in this test procedure may be performed out of sequence or repeated as required, but only by authorization and direction of the PI.


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4. DESCRIPTION OF TEST METHOD A “pull-down” test method will be used to conduct the experiments. Figure A-1 shows the conceptual schematic of this method. It consists of three test periods under full-recirculation mode of the chamber operation: VOC injection period, static period and dynamic period. The injection of known amount of contaminants into the experimental system, followed by a quasi-static period, result in stable initial high concentration levels. The time when the air cleaner is turned on is defined as time zero, at which the dynamic period begins. Using the measured concentration decay rate from the dynamic period, the clean air delivery rate (CADR) of the cleaner can then be calculated for each VOC and different size particles.

Figure A-1 Conceptual schematic of “pull-down” test method An empty chamber test should be conducted to determine the influence of empty chamber itself on VOC and particle concentrations before the test for room air cleaner. For each air cleaner test, the air cleaner will be placed inside the chamber before injection period.

5. TEST EQUIPMENT AND MATERIALS (1) Test Equipment for VOCs

(a) ATD-GC/MS (or ATD-GC/FID) system for sorbent tube analysis, (b) Sorbent sampling tubes for off-line individual VOC analysis (Stainless steel tube packed with

Tenax TA and Carboxen 569 are used for sampling), (c) Sampling pumps, (d) Heater (Hot plate) for evaporating VOCs (up to 250oC), (e) Electronic balance (1mg or better solution), (f) INNOVA 1312 Photoacoustic multi-gas monitor for continuous monitoring TVOC,

formaldehyde and tracer gas.

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(2) Test equipment for particles

(a) TSI Model 8108 Large- Particle Aerosol Generator, (b) TSI Model 3321 Aerodynamic Particle Sizer Spectrometer for online measurement of

concentrations of particles ranging from 0.5 to 20 µm in diameter, (c) LASAIR Model 1003 Aerosol Particle Counter for measurement of concentrations of particles

ranging from 0.1 to 0.5 µm in diameter. (3) Other Equipment

(a) M265A ozone analyzer. (b) IAQ-Calc 8762 meter for temperature and relative humidity measurements

(4) Materials

(a) Selected test VOCs (pure compound), (b) Tracer gas (SF6), (c) Potassium chloride (KCl) powder.

6. TEST PREREQUISITES

(1) Faculty Advisor permission has been obtained to commence testing. (2) Personnel performing this procedure have participated in a pre-test briefing and have read and

understand the procedure Precautions and Limitations, (3) Verify chambers are in position with all control and experimental requirements (i.e. HVAC

system control accuracy) satisfied, (4) No other testing or other work in progress that could impact performance or results of this test, (5) Sampling and measurement equipment has been supplied calibrated.

7. TEST PROCEDURES 7.1 Empty Environmental Chamber Characterization

7.1.1 Condition the sorbent sampling tubes to be used.

7.1.2 Establish Reference Conditions

7.1.2.1 Place the hot plate (preset at level 5 which equals a heating temperature of approximate 200 - 230oC), the Aerodynamic Particle Sizer Spectrometer and the Aerosol Particle Counter inside the chamber. Locations of all equipments inside the chamber are shown in Figure A-2. For particulates, the sampling point is located in the middle of the chamber and 1.5 m above the floor. For VOCs, sorbent tube samples will be taken at the return air duct and/or the sampling ports at the chamber side.


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Figure A-2 Equipment locations for empty chamber test

7.1.2.2 Set up Andover system to monitor chamber parameters (including temperature, pressure, RH and airflow), making sure that the control is in good standing. 7.1.2.3 Set up ozone analyzer to continuously monitor the ozone level.

7.1.2.4 Set up 1312 photoacoustic multi-gas monitor to continuously monitor TVOC, formaldehyde and tracer gas concentration.

7.1.2.5 Set up APS 3321 and APC 1003 to continuously monitor particle concentrations.

7.1.2.6 Set up IAQ-Calc 8762 meter to continuously monitor temperature and relative humidity in the testing chamber.

7.1.2.7 Flush and pre-condition the chamber with clean make-up air (100 CFM / 7 ACH airflow, 21 oC, 50% RH) for at least 24 hours.

7.1.2.8 Collect tube sample on the return air duct right out of the chamber, which will serve as background VOCs concentrations for later data analysis. 7.1.3 Perform Test

7.1.3.1 After 24 h flushing of the chamber, separate the chamber from the HVAC system by switching the dampers to the modified recirculation loop. Set the recirculating fan at the desired level (130 CFM). The chamber is now running under full-recirculation mode.

7.1.3.2 Use tracer gas to check air tightness of the chamber system. Either CO2 or SF6 will be injected before the beginning of the test and monitored continuously during the entire test period 7.1.3.3 VOCs Preparation and Injection

7.1.3.3.1 Preparation of tested VOCs. Weigh two clean glass bottles with cap and two petri dishes first. For liquid VOC, use syringe to inject the calculated amount of each VOC liquid (target 24 mg which

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equals to approximately 1mg/m3 initial chamber concentration) to a glass bottle with septum, respectively. The uncertainty related with injection amount will be determined from the accuracy and resolution of syringe. After injection of each compound, use the electronic balance to weigh the total weight for double check. Formaldehyde will be generated by directly heating solid paraformaldehyde, which needs to be put in a separate bottle. The target amount of formaldehyde is 48 mg (equal to approximately 2 mg/m3 initial chamber concentration).

7.1.3.3.2 Injection of tested VOCs. Quickly open the chamber door and bring the two glass bottles (one for formaldehyde and one for mixture of other VOCs) into the chamber. Pour the solid paraformaldehyde into one petri dish on hot plate, and bring the empty bottle and cap out when out of the chamber. Pour the VOC mixtures into the other petridish on hot plate, leaving the bottle (on hot plate to facilitate the evaporation of VOC residuals inside the bottle) and the cap inside the chamber. Then quickly move out of the chamber and close the chamber door. The whole process will take approximately 1 to 2 minutes.

7.1.3.3.3 Turn on the power of hot plate from chamber control panel. Record this time as the test beginning time. 7.1.3.3.4 Turn off the power of hot plate after 1 h. The injection period for VOCs will be 1 h.

7.1.3.4 Particles Preparation and Injection

7.1.3.4.1 Prepare 30% KCl solution and fill it into the container of the TSI Model 8108 Particle Generator.

7.1.3.4.2 Adjust the air regulator of particle generator to 50psi. Adjust the atomizer air flow and drying air flow to 1 and 4 SCFM, respectively. Turn the pump controller to setting 10 until the liquid column reaches the spray cover. Then adjust to 2.

7.1.3.4.3 After 5 minutes’ stabilization, begin to inject particles by switching the 3-way valve to the injection side. After 1 minute, stop injection by switching the 3-way valve to exhaust mode and shut down particle generator. The time point for injecting particles will be 25 minutes before dynamic period.

7.1.3.5 Dynamic Test Period and Sampling Schedule 7.1.3.5.1 At the end of this quasi-static period, all on-line monitors will be continuously running and duplicate tube samples will be collected.

7.1.3.5.2 The chamber will continuously run under full-recirculation mode for another 6 hours. Samples of sorbent tubes will be taken at approximately 5 min, 10min, 15min, 20min, 30min, 45min, 1h, 1.5 h, 2 h, 3 h, 4.5 h, 6 h, respectively. At least 20% duplicate samples should be taken. All on-line monitors will be continuously running. Results will serve as the baseline values for the empty chamber.

7.1.4 Chamber Flush. Once the test is done, switch the chamber back to HVAC system side, set the system to single-through operation mode and flush the chamber with clean make-up air (100 CFM) to remove the VOC and particle residuals inside the chamber, which will last for a minimum of 24 hours.

7.1.5 Data Acquisition

7.1.5.1 Take picture of experimental set-up

7.1.5.2 Summarize data for amounts of injected VOCs

7.1.5.3 Download photoacoustic multi-gas monitor data

7.1.5.4 Download particle data

7.1.5.5 Download HVAC system performance data

7.1.5.6 Download ozone data


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7.1.5.7 Download IAQ-Calc 8762 meter data

7.1.5.8 Conduct tube analysis by the ATD-GC/MS (or ATD-GC/FID) system and summarize the data

7.1.6 Data analysis and characterize influence of chamber system (i.e., air-tightness, particle natural deposition rate and VOC sink effect)

7.2 Pull-down Test for Portable Room Air Cleaner

7.2.1 Condition the sorbent tubes to be used.


7.2.2.1 Place the hot plate (preset at level 5 which equals a heating temperature of approximate 200 - 230oC), the Aerodynamic Particle Sizer Spectrometer and the Aerosol Particle Counter inside the chamber. Place the air cleaner to be tested inside the chamber and set the desired operation level (highest currently). Locations of equipments and the test air cleaner inside the chamber are shown in Figure A-3. For particulates, the sampling point is located in the middle of the chamber and 1.5 m above the floor. For VOCs, sorbent tube samples will be taken at the return air duct and/or the sampling ports at the chamber side.

Figure A-3 Equipment locations for portable room air cleaner test





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7.2.3.1 After 24 h flushing of the chamber, separate the chamber from the HVAC system by switching the dampers to the modified recirculation loop. Set the recirculating fan at the desired level (130 CFM). The chamber is now running under full-recirculation mode.

7.2.3.2 Use tracer gas to check air tightness of the chamber system. Either CO2 or SF6 will be injected before the beginning of the test and monitored continuously during the entire test period

7.2.3.3 VOCs Preparation and Injection

7.2.3.3.1 Preparation of tested VOCs. Weigh two clean glass bottles with cap and two petri dishes first. For liquid VOC, use syringe to inject the calculated amount of each VOC liquid (target 24 mg which equals to approximately 1mg/m3 chamber concentration) to a glass bottle with septum, respectively. The uncertainty related with injection amount will be determined from the accuracy and resolution of syringe. After injection of each compound, use the electronic balance to weigh the total weight for double check. Formaldehyde will be generated by directly heating solid paraformaldehyde, which needs to be put in a separate bottle. The target amount of formaldehyde is 48 mg (equal to approximately 2 mg/m3 chamber concentration).

7.2.3.3.2 Injection of tested VOCs. Quickly open the chamber door and bring the two glass bottles (one for formaldehyde and one for mixture of other VOCs) into the chamber. Pour the solid paraformaldehyde into one petri dish on hot plate, and bring the empty bottle and cap out when out of the chamber. Pour the VOC mixtures into the other petridish on hot plate, leaving the bottle (on hot plate to facilitate the evaporation of VOC residuals inside the bottle) and the cap inside the chamber. Then quickly move out of the chamber and close the chamber door. The whole process will take approximately 1 to 2 minutes.

7.2.3.3.3 Turn on the power of hot plate from chamber control panel. Record this time as the test beginning time. 7.2.3.3.4 Turn off the power of hot plate after 1 h. The injection period for VOCs will be 1 h.

7.2.3.4 Particle Preparation and Injection



7.2.3.4.3 After 5 minutes’ stabilization, begin to inject particles by switching the 3-way valve to the injection side. After 1 minute, stop injection by switching the 3-way valve to exhaust mode and shut down particle generator. The time point for injecting particles will be 25 minutes before dynamic period. 7.2.3.5 Dynamic Test Period and Sampling Schedule

7.2.3.5.1 At the end of this quasi-static period, all on-line monitors will be continuously running and duplicate tube samples will be collected. Results will serve as the initial concentrations of the dynamic period.


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7.2.3.5.2 Turn on the power of room air cleaner from chamber control panel at the beginning of dynamic period. The dynamic period will be 6 hours. Samples of sorbent tubes will be taken at approximately 5 min, 10min, 15min, 20min, 30min, 45min, 1h, 1.5 h, 2 h, 3 h, 4.5 h, 6 h, respectively. At least 20% duplicate samples should be taken. The sampling volumes may change according to the contaminant concentration levels.

7.2.4 Chamber Flush. Once the test is done, turn off air cleaner and switch the chamber back to HVAC system side, set the system to single-through operation mode and flush the chamber with clean make-up air (100 CFM) to remove the VOC and particle residuals inside the chamber, which will last for a minimum of 24 hours. 7.2.5 Data acquisition

7.2.5.1 Take the picture of experimental set-up and the test product


7.2.5.3 Download Photoacoustic multi-gas monitor data





7.2.5.8 Conduct tube analysis by the ATD-GC/MS (or ATD-GC/FID) system and summarize the data

7.2.6 Data analysis

7.2.6.1 Characterize the chamber air tightness

7.2.6.2 Conduct concentration vs. time curve for each test VOC and different size particle. Normalized concentrations (i.e., concentration divided by the initial concentrations at the beginning of dynamic period) may be used to facilitate the comparison 7.2.6.3 Characterize performance of the tested room air cleaner by CADR (clean air delivery rate)

7.3 Pull-down Test for In-Duct Air Cleaner

7.3.1 Condition the sorbent tubes to be used.


7.3.2.1 Place the hot plate (preset at level 5 which equals a heating temperature of approximate 200 - 230oC), the Aerodynamic Particle Sizer Spectrometer and the Aerosol Particle Counter inside the chamber. Install the in-duct air cleaner to be tested on the filter frame and seal it properly. Locations of equipments and the test air cleaner are shown in Figure A-4. For particulates, the sampling point is located in the middle of the chamber and 1.5 m above the floor. For VOCs, sorbent tube samples will be taken at the return air duct and/or the sampling ports at the chamber side.

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Figure A-4 Equipment locations for in-duct air cleaner test





7.3.2.7 Set up DP sensor to continuously monitor the pressure drop across the in-duct filter test frame.



7.3.3.1 After 24 h flushing of the chamber, separate the chamber from the HVAC system by switching the dampers to the modified recirculation loop. Set the recirculating fan at desired flow rate (i.e. 800 CFM) and periodically check it with velocity meter measurement. The valves in the in-duct filter testing section should be in the bypass side. The chamber is now running under full-recirculation mode without going through the frame for the test filter.

7.3.3.2 Use tracer gas to check air tightness of the chamber system. Either CO2 or SF6 will be injected before the beginning of the test and monitored continuously during the entire test period

7.3.3.3 VOCs Preparation and Injection 7.3.3.3.1 Preparation of tested VOCs. Weigh two clean glass bottles with cap and two petri dishes first. For liquid VOC, use syringe to inject the calculated amount of each VOC liquid (target 24 mg which equals to approximately 1mg/m3 chamber concentration) to a glass bottle with septum, respectively. The uncertainty related with injection amount will be determined from the accuracy and resolution of syringe. After injection of each compound, use the electronic balance to weigh the total weight for double check.


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Formaldehyde will be generated by directly heating solid paraformaldehyde, which needs to be put in a separate bottle. The target amount of formaldehyde is 48 mg (equal to approximately 2 mg/m3 chamber concentration).

7.3.3.3.2 Injection of tested VOCs. Quickly open the chamber door and bring the two glass bottles (one for formaldehyde and one for mixture of other VOCs) into the chamber. Pour the solid paraformaldehyde into one petri dish on hot plate, and bring the empty bottle and cap out when out of the chamber. Pour the VOC mixtures into the other petridish on hot plate, leaving the bottle (on hot plate to facilitate the evaporation of VOC residuals inside the bottle) and the cap inside the chamber. Then quickly move out of the chamber and close the chamber door. The whole process will take approximately 1 to 2 minutes. 7.3.3.3.3 Turn on the power of hot plate from chamber control panel. Record this time as the test beginning time.

7.3.3.3.4 Turn off the power of hot plate after 1 h. The injection period for VOCs will be 1 h.

7.3.3.4 Particle Preparation and Injection



7.3.3.4.3 After 5 minutes’ stabilization, begin to inject particles by switching the 3-way valve to the injection side. After 1 minute, stop injection by switching the 3-way valve to exhaust mode and shut down particle generator. The time point for injecting particles will be 25 minutes before dynamic period. 7.3.3.5 Dynamic Test Period and Sampling Schedule

7.3.3.5.1 At the end of this quasi-static period, all on-line monitors will be continuously running and duplicate tube samples will be collected. Results will serve as the initial concentrations of the dynamic period.

7.3.3.5.2 Quickly switch the valves from bypass side to the test filter frame side at the beginning of dynamic period. The chamber is now running under full-recirculation mode with the airflow going through the test filter. The dynamic period will be 6 hours. In general, samples of sorbent tubes will be taken at approximately 5 min, 10min, 15min, 20min, 30min, 45min, 1h, 1.5 h, 2 h, 3 h, 4.5 h, 6 h, respectively. At least 20% duplicate samples should be taken. However, the sampling schedule may change depending on how fast the contaminant concentrations decrease. The sampling volumes may also change according to the contaminant concentration levels.

7.3.3.5.3 Quickly switch the valves back from test filter frame side to bypass side.

7.3.4 Chamber Flush. Once the test is done, turn off the air cleaner and switch the chamber back to HVAC system side, set the system to single-through operation mode and flush the chamber with clean make-up air (100 CFM) to remove the VOC and particle residuals inside the chamber, which will last for a minimum of 24 hours.

7.3.5 Data acquisition

7.3.5.1 Take the picture of experimental set-up and the test product


7.3.5.3 Download Photoacoustic multi-gas monitor data


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7.3.5.8 Record the DP sensor data

7.3.5.9 Conduct tube analysis by the ATD-GC/MS (or ATD-GC/FID) system and summarize the data 7.3.6 Data analysis

7.3.6.1 Characterize the chamber air tightness

7.3.6.2 Conduct concentration vs. time curve for each test VOC and different size particle. Normalized concentrations (i.e., concentration divided by the initial concentrations at the beginning of dynamic period) may be used to facilitate the comparison

7.3.6.3 Characterize performance of the tested air cleaner by CADR (clean air delivery rate)

APPENDIX C: COMPARISON OF TESTED AIR CLEANERS FOR REMOVING HEXANE, ISO-BUTANOL, 2-BUTANONE, DECANE AND

TETRACHLOROETHYLENE

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APPENDIX C: COMPARISON OF TESTED AIR CLEANERS FOR REMOVING

HEXANE, ISO-BUTANOL, 2-BUTANONE, DECANE AND TETRACHLOROETHYLENE

Device No. CADR (CFM) Removal efficiency

(%) Watts/CFM CADR Purchase $/CFM CADR

Ozone generation

Hexane

P1 123 49 1.1 2.0 No P2 91 40 2.6 8.7 No P3 1.9 0.5 35.3 263 Yes (1.696 mg/h) P4 232 60 0.5 2.4 No P5 0.3 - 24.0 1163 Yes (2.267 mg/h) P6 88 38 0.6 5.3 No D1 599 91 0 0.9 No D2 13 2 10.9 108 No

Iso-butanol P1 138 55 1.0 1.8 No P2 96 42 2.4 8.3 No P3 5 1.3 13.4 100 Yes (1.696 mg/h) P4 246 64 0.5 2.3 No P5 0.5 - 14.4 698 Yes (2.267 mg/h) P6 151 65 0.3 3.1 No D1 511 78 0 1.0 No D2 98 15 1.4 14.3 No

2-butanone P1 127 51 1.1 2.0 No P2 91 40 2.6 8.7 No P3 1.4 0.4 47.9 356 Yes (1.696 mg/h) P4 223 58 0.6 2.5 No P5 0.2 - 36.0 1745 Yes (2.267 mg/h) P6 91 39 0.6 5.2 No D1 604 92 0 0.8 No D2 52 8 2.7 26.9 No

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Device No. CADR (CFM) Removal efficiency

(%) Watts/CFM

CADR Purchase $/CFM

CADR Ozone generation

Decane P1 128 51 1.1 1.9 No P2 78 34 3.0 10.2 No P3 22 6 3.0 22.7 Yes (1.696 mg/h) P4 188 49 0.7 3.0 No P5 0.4 - 18.0 873 Yes (2.267 mg/h) P6 115 50 0.4 4.1 No D1 482 73 0 1.1 No D2 34 5 4.2 41.2 No

Tetrachloroethylene P1 142 57 1.0 1.8 No P2 99 44 2.4 8.0 No P3 6 2 11.2 83.2 Yes (1.696 mg/h) P4 235 61 0.5 2.4 No P5 0.4 - 18.0 873 Yes (2.267 mg/h) P6 129 56 0.4 3.6 No D1 591 90 0 0.9 No D2 5 1 28.4 280 No

Notes:

(1) Results for toluene, formaldehyde and dichloromethane had been reported in Table 21;

(2) Reported CADR was equivalent average CADR number over test period (CADR_6h) defined in Equation 7 and reported removal efficiency was this average CADR number divided by the measured airflow rate through the air cleaner when the measured VOC concentrations could not directly fit the exponential decay;

(3) Removal efficiency was not calculated for product P5 (ionizer) because its flow rate was not measured;


(5) For in-duct air cleaners, additional fan power requirement due to the pressure drop increase was not included;

(6) For column of ozone generation, values in “( )” were the estimated ozone generation rate based on the measured concentration increase during the 6 hr test period. The ozone generation of product P3 was due to the electronic cell for particulate removal.

APPENDIX D: EXAMPLE ENERGY COST CALCULATION BY STEADY-STATE METHOD

NCEMBT-061005


Base Case - 0.15 ACH infiltration + 0.2 ACH mechanical ventilation = 0.35 ACH total air exchange rate House Structure Information

Type Single-family home Floor area 2300 ft^2 214 m^2 (assuming a ceiling height of 2.4m)

House volume 18110 ft^3 513 m^3 House Location Information

City Chicago, IL Weather data see "weather data" sheet

Energy price Fuel Price $1.00260 $/therm $(0.1449+0.8577) = $1.0026 for first 20 therms $0.91300 $/therm $(0.0553+0.8577) = $0.913 for 21 - 50 therms

$0.90960 $(0.0519+0.8577) = $0.9096 over 50 therms

$/therm Electricity price $0.08275 (no demand charge)$/kWh

Air Change Rate infiltration 0.15 ACH 45.3 CFM

mechanical ventilation 0.2 ACH 60.4 CFMequivalent clean air from air cleaner 0 ACH 0.0 CFM

Total 0.35 ACH 105.6 CFMDesign Parameters

Heating and humidification setpoint Indoor setpoint 71 F 21.7 oC 45 grains of H20 per lb of Air (or 40% RH) Heating if outdoor temp < 66 F 18.9 oC (assume 5 F temperature increase from internal gains) Humidify if outdoor temp < 66 F and outdoor RH < 45 grains of H20 per lb of Air (or 40% RH)

Cooling and dehumidification setpoint Indoor setpoint 76 F 24.4 oC 67 grains of H20 per lb of Air (or 50% RH) Cooling if outdoor temp > 71 F 21.7 oC (assume 5 F temperature increase from internal gains) Dehumidify if outdoor temp >

71 F and outdoor RH >

67 grains of H20 per lb of Air (or 50% RH)

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Equipment efficiency (from Building America Benchmark) Furnace (heating) EFF 0.8 AC EER 10 Btu / W - hr cooling COP 2.93 Water heater (humidification) EF 0.6 (Capacity 50 gallons) Air properties

Density(pou) at 66 F (for heating season) 0.0755 lb/ft^3 1.210 kg/m^3 at 71 F (for cooling season) 0.0748 lb/ft^3 1.198 kg/m^3

Specific heat (Cp) at 66 F (for heating season) 0.2403 Btu/(lbm-F) at 71 F (for cooling season) 0.2403 Btu/(lbm-F)

Heat of vaporization of water (hfg) 2260 kJ/kg 971 Btu/lb Energy Consumption Calculation (I) Fan Power energy due to mechanical ventilation

Fan Power/CFM 0.5 watts/cfm Annual Fan Energy (1) 264.4 kWh (assume 24/7/365 operation)

Annual Fan Energy Cost (1) $21.88 (II) HVAC Energy Analysis for mechanical ventilation Heating and humidification

Heat [Q*pou*Cp*sum(ti-to)/EFF] 13512953 Btu 135.130 therms (1 therms = 10^5 Btu) Humidification [Q*pou*hfg*sum(Wi-Wo)/EF] 7035800 Btu 70.358 therms (1Btu = 0.000293 kwh)

Total 20548754 Btu 205.488 therms (1 grains = 0.000143 lb) Cost $188.87

Cooling and dehumidification Sensible [Q*pou*Cp*sum(to-ti)/EER] 70844 W-hr 70.8 kwh Latent [Q*pou*hfg*sum(Wi-Wo)/EER] 119674 W-hr 119.7 kwh

Total 190518 W-hr 190.5 kwh Cost $15.77

Net HVAC Cost (2) $204.64

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93

Total Electricity 454.9 kWh Total natural gas

205.5 therms

Electricity cost $37.65 Natural gas cost $188.87 Total Cost (1)+(2) $226.52 Cost per CFM outdoor air $3.75

Cutoff $/CFM pollutant free air to compete with mechanical ventilation cost (assuming negligible heat gain impacts due to air cleaner operation)

$3.75

NCEMBT-

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