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NIH Design Requirements Manual 1Section 6.1

Section 6.1 HVAC DESIGN

6.1.0 General

6.1.1. Heating, Ventilation, and Air-Conditioning Systems for NIH Facilities1. Heating, ventilation, and air-conditioning (HVAC) systems for NIH Facilities shall be

designed to achieve the following general criteria:(a) Maintain space temperature and humidity at the required set points and filtration at

prescribed levels.(b) Be reliable, redundant and operate without interruption.(c) Meet Federal sustainable design and energy conservation standards and provide a

proper control system.(d) Maintain prescribed space background noise criteria, generated by HVAC systems.(e) Provide ventilation to remove fumes, odors, and airborne contaminants.

2. Laboratory spaces and animal facilities shall meet the requirements in the “Biosafety in Microbiological and Biomedical Laboratories” published by Center for Disease Control and Prevention and NIH.

3. Animal Facilities shall meet the requirements in the “Guide for the Care and Use of Laboratory Animals” published by the Institute of Laboratory Animal Resources.

4. The design of teaching Laboratories shall be based on function and on the hazard assessment made in conjunction with the users and DOHS.

5. The design of Clinical Laboratories located within the hospital environment shall be based on the Facility Guidelines Institute (FGI) standards and ventilation shall follow the latest ASHRAE 170 standards. Where infectious samples or biohazard materials or hazardous chemicals are involved, the A&E shall follow appropriate requirements per the NIH Biosafety levels, the DRM requirements for laboratories and consult with user and DOHS. Data Center design shall follow the latest ASHRAE standards and the NIH Guidelines for Data Center located in Appendix.

6. The Pharmacy and Radio-pharmacy shall comply with (US Pharmacopeia) USP-797 guidelines. The Drug/Bio-pharmaceutical manufacturing/processing used for human clinical trials shall follow the cGMP (Good Manufacturing Practice) and applicable CFR, (Code of Federal Regulation), ICH (International Conference on Harmonization) and FDA (Federal Drug Administration) guidelines.

7. The design of administrative buildings and spaces shall be based ASHRAE standards, and will comply with latest International and local mechanical codes. Specific requirements for the administrative areas are included in the Office Fit Out Guidelines located in the Appendix.

The general criterion applies to all NIH facilities including non-laboratory and non- animal areas. For NIH facilities, the non-labs and non-animal research areas shall also comply with the associated standards, local codes and guidelines attached in the Appendix of this


document. For example, the ventilation requirements for offices shall follow the latest ASHRAE 62.1 standardsTeaching laboratories are different from research laboratories since they typically do not involve on-going research, the hazard level and operating hours may be lower for teaching laboratory and teaching labs may tolerate shutdowns for replacement and maintenance. Hence the redundancy requirements for research laboratories may not be applicable for teaching laboratories. Where teaching laboratories are also used as research laboratories, the requirements of research laboratories will apply. The pharmacy and Radio-pharmacy shall comply with (US Pharmacopeia) USP-797 guidelines. Drug/Bio-pharmaceutical manufacturing/processing for clinical trials shall follow the cGMP (Good Manufacturing Practice) and applicable CFR and FDA guidelines.

6.1.2. Cognizance of DRM and Associated Standards The A/E shall be cognizant of additional requirements in other sections of the DRM, as well as associated standards as applicable to the facility type. Many requirements related to HVAC systems are discussed elsewhere in the DRM and in referenced standards. Basic requirements are covered in codes and standards, and additional requirements may be found in related referenced documents. The A/E must be cognizant of these requirements and coordinate with other disciplines to provide DRM compliant and appropriate design.

6.1.3. Applicable Codes and Standards:The A/E shall comply with the design and safety guidelines and references listed in Appendix A as well as other requirements received or directed from the NIH Project Officer or required by the program. The A/E shall utilize the latest editions of referenced codes, standards, and design and safety guidelines available at the time of the design contract award.

In cases of conflict between the adopted or selected code/ standard and the NIH DRM, the most stringent, technically appropriate, and conservative criteria shall apply. The code is typically a minimum standard, and in many cases the DRM is most stringent. Where it is unclear which criteria are to be applied, application for clarification may be made through the project officer.

There are numerous industry guidelines and standards that must be followed in concert with the NIH Design Requirements Manual. Projects in the leased buildings in Maryland shall be in conformance with both DRM and the Code of Maryland Regulations (COMAR) unless otherwise noted. NIH allows waiver on DRM requirements on leased buildings based on the length of the leased. Refer to leased facility waiver checklist in the Appendix X for additional information.

6.1.4. General Planning RequirementsThe arrangement of HVAC systems shall ensure maximum reliability, operational flexibility, and capacity for renovation without affecting other areas or interfering with research; shall allow service to occur outside critical and clean spaces without interfering with research; consider service access restrictions and security requirements; and shall minimize potential for disruption due to single point failures and routine maintenance. Designs shall accommodate future program renovations, expansions, serviceability, and changes of equipment. System designs must consider future capacity allowances and a cognizance of future expansion and renovation strategies, including forethought in the sizing and arrangement of utility services, main and branch duct systems, as well as equipment room space planning forethought and interdisciplinary coordination. The design intent shall be sufficiently documented, including explanation of provisions to facilitate projected future requirements.


Access panels shall be of appropriate size and type, and their locations shall be clearly noted in the design documents.

The arrangement of HVAC systems shall be coordinated with the arrangement of the laboratory planning modules so as to promote operational flexibility. Such planning should be documented so that the intended provisions may be understood and maintained). Thoughtful consideration of access restrictions and security issues are beneficial to minimizing impact on facility operations.

6.1.5. Systems Failure and Disaster MitigationSystems shall be designed and materials selected to minimize potential for loss of service and to limit impact on research and vivarium operations in the event of disaster or malfunction. Throughout the planning and design stages, the A/E shall evaluate each system to assess potential steps that may be taken to alleviate future damages, service disruptions, and promote rapid restoration of temporary and normal services. Failures in HVAC systems can cause substantial impact to facility operations and loss of research. While many catastrophic utility failures can be prevented or controlled by provision of redundant equipment and appropriate standby power supplies, utilizing freeze protection measures, commissioning activities and BAS monitoring; these specific additional precautions should be addressed in the design of HVAC systems for research and vivarium along with an evaluation of additional risks in conjunction with the program. The rapid restoration of services and minimization of damage is critical in any emergency and is best accommodated through careful planning and installation quality control. Additional provisions may be found in the requirements for each system.

6.1.6. Energy Efficiency and Water Conservation: Systems shall be designed and equipment selected using best practices to achieve optimal energy efficiency and water conservation, without compromising the research program, safety, reliability, or the requirements within the NIH Design Requirements Manual, code, and referenced standards. Approaches must be cost-effective, durable, holistically considered, and present a reasonable payback (Follow federal guidelines such as EISA 2007). The project with a payback less than 10 to 15 years is highly favorable. Energy and water conservation not only are federal mandates, but required of responsible design. Design approaches to achieve water and energy conservation must not be focused only on that goal, but must maintain the safe and reliable operations of the facility. Approaches must be cost-effective over the lifecycle of the facility and present a reasonable payback. Thoughtful consideration is required in reviewing sustainability approaches to ensure the solution is ultimately beneficial, energy-efficient, cost-effective, and does not otherwise compromise operations. The goal is not about just achieving “points” in a scoring system, but rather to utilize justified practices that provide holistic benefits.

6.1.7. Heating and Cooling Load CalculationsComplete heating and cooling load calculations and a vapor drive study (where applicable) shall be prepared for each space within a design program and presented in a format similar to that outlined in the ASHRAE Handbook of Fundamentals. Heating and cooling load calculations are required for all projects to facilitate review and provide a reference for system modifications. Individual room calculations shall be generated and summarized on a system basis and presented with a block load to define the peak system load. Load summary sheets shall indicate: area of individual rooms, supply air quantity, L/s (cfm), ACH, and corresponding exhaust air quantity. Calculations shall include, but are not limited to: indoor and outdoor design parameters, heat gains and heat losses, supply and exhaust requirements for central systems,


and for each area of the facility, humidification and dehumidification requirements, and heat recovery.

6.1.8. Laboratory Equipment Cooling Loads1. The HVAC system shall provide, as a minimum, a cooling capacity for 1,892 W (6,455

BTUH) (sensible heat) for laboratory equipment in a typical 22 m2 (237 ft2) laboratory module (8 Watts per sqft) _ or cooling for the actual calculated load, whichever is greater.

2. The A/E shall make a detailed and complete inventory of all laboratory equipment scheduled for installation in each space and determine the projected equipment load requirement using estimated diversity factors. The A/E should evaluate equipment nameplate ratings, heat release data and usage factors and overall diversity.

3. The detailed cooling load calculation including equipment diversity factors shall be indicated in the Basis of Design report.

4. The A/E shall evaluate the following rooms used for laboratory support, often having higher than normal cooling loads, as well as evaluating the use of supplemental cooling units to offset excessive sensible loads affecting these areas, while maintaining minimum ventilation requirements:(a) Common equipment rooms(b) Autoclave rooms(c) “Clean” and “dirty” cage wash rooms(d) Glassware washing rooms(f) Special function rooms(g) Electron microscope rooms (h) Bio-Informatics/Robotics labs (i) Labs associated with physics such as Lasers, Optics and nuclear material

The minimum 8W/sqft for equipment load may be used for generic labs and as a planning tool where all the equipment has not yet been specified. It is required that the A&E use actual equipment data for calculating actual loads Labs at NIH facilities have tended to be equipment intensive and prone to equipment creep as scientists add more table top equipment over time.

Due to lack of data on parameters such as nameplate data, heat release date and usage factors, it is often difficult to analytically derive the equipment loads. As a result, designers typically assume the worst case for each of these parameters, thereby grossly overestimating the actual equipment loads. It is not recommended to use instantaneous peak load as the basis for calculating heat release. What is more important is average peak load. Generally space temperatures are not sensitive to instantaneous peaks of a few seconds and therefore it is unnecessary to size HVAC systems based on peak instantaneous power. It is rare for all equipment simultaneously and most equipment operates with duty cycles below nameplate ratings. The purpose of determining the actual equipment load data is to right size the HVAC equipment to lower initial construction cost as well as life cycle energy cost.

Information on some of the common equipment can be found in the ASHRAE Laboratory Design Guide. The Labs 21 benchmarking database also provides data on energy use and demand

If snorkel exhaust is used near equipment, the convective portion of the equipment can be discounted from the space cooling load. Also, heat from equipment that is directly vented or


heat from water cooled equipment should not be considered part of the heat release into the room.

6.1.7.2. Animal Room Cooling LoadsThe central HVAC system shall be able to remove both sensible and latent heat produced by laboratory animals. The total heat gain for animals is function of weight and the metabolic rate of each animal. Heat generation from animals for the purpose of HVAC load calculations shall be as listed in the ASHRAE Application Handbook.

6.1.8. Animal DensityA typical 3 m (10 ft.) by 7 m (23 ft.) animal holding module shall be designed to the animal population density shown in Figure 1.

Figure 1. Design Density for Animal PopulationsDesign Animal DensitySpecies Animals per Rack Racks per Module Animals per ModuleMouse 300 5 1500Rat 90 5 450Guinea pig 40 5 200Rabbit 8 5 40Cat 8 5 40Nonhuman primate 8 5 40Outdoor Design Conditions6.1.7.1. Occupancy LoadsThe A/E shall base HVAC load calculations on the expected occupancy in each space and the activity level as per ASHRAE Fundamentals Handbook.

6.1.10. Lighting LoadsPlease refer to DRM electrical section and ASHRAE 90.1 for the lighting load requirements. The A/E shall base HVAC load calculations on actual lighting loads.

6.1.11. Outdoor Design Conditions1. All facilities shall be designed in accordance with the climatic conditions listed in

ASHRAE Handbook of Fundamentals. For summer conditions, use 0.4% column dry bulb (DB) / mean coincident wet bulb (WB) temperatures. For winter conditions, use 99.6% column DB temperature. Summer mean coincident wind speed (MCWS) shall be 0.4% DB column. Winter MCWS shall be 99.6% DB column. See Figure 3 for outdoor design conditions for Bethesda and Poolesville campuses.

2. Sizing of evaporative type cooling towers shall be based on 1°C (2°F) higher than the WB temperature shown in the 0.4% column (10a) shown in the ASHRAE Handbook of Fundamentals.

3. All approved outdoor air-cooled condensing equipment for Bethesda shall be designed and selected on the basis of 35°C (95°F) ambient temperature.

Figure 3. Outdoor Design Conditions (Bethesda)Outdoor Design Conditions


Season Temperature °C (°F) Wind Speed m/s (mph)Summer 35.0 (95) DB, 25.6 (78)

MCWB5.4 (12)

Winter - 11.6 (11) DB 4.8 (10)Evaporative cooling 26.7 (80) WB n/adoor Design Conditions6.1.12. Energy Conservation/Efficiency/Recovery

1. The A/E shall utilize the latest edition of the following energy codes and standards to design the exterior envelope for selecting HVAC and mechanical systems. (a) ASHRAE Standard 90.1(b) ASHRAE 189.1 (c) NFPA Standard 45(d) ANSI Standard Z9.5 (e) International Energy Conservation Code(f) All applicable federal mandates, executive orders, codes and standards for

energy efficiency and sustainable design

2. Efforts to reduce energy must not compromise safety requirements required by NIH Division of Safety (NIH/DOHS). These systems must maintain the required environmental conditions at all times.

3. Energy conservation measures must be both appropriate to NIH facility and have reasonable payback.

4. For laboratories, it is encouraged to use variable volume control of exhaust air through fume hoods by reducing exhaust airflow when the fume hood sash is not open.

5. It is encouraged to use room cooling hydronic HVAC systems such as chilled beams that decouple the room cooling function from the ventilation function and minimize reheat. .

6. Due to mainly once through supply air systems in laboratories and animal research facilities, significant energy is lost as exhaust. A&E shall utilize energy recovery systems for energy conservation, but these should be balanced against risk of cross contamination from exhaust to supply stream. . The risk for potential cross-contamination of chemical and biological materials from exhaust air to intake air and potential for corrosion and fouling of devices located in the exhaust airstream should be evaluated.

7. When evaluating energy recovery costs, all costs (pumping, air pressure drops, etc.) on both sides of the equation should be evaluated. It is recommended that some level of degradation due to fouling be included in the calculation.

8. Run-around coils are used to recover sensible heat from exhaust air steam to the outside air stream, via coils, and glycol piping and pumps. There is no risk of cross contamination between exhaust and intake air. Combination heat recovery-preheat coils should be avoided due to complications in controlling and possibility of overheating intake air in summer time. Roughing filters shall be used upstream of exhaust coil serving animal facilities and corrosion protection should be applied in exhaust coils serving laboratories.


9. Energy recovery heat recovery wheels recover total energy (sensible and latent) and are more efficient than sensible heat recovery systems. They require supply and exhaust ductwork configuration to be adjacent at the heat recovery device. There is potential for cross contamination from exhaust to supply. Exhaust from fume hoods and chemical storage rooms shall not be permitted to pass through heat wheel system. Energy recovery wheels are permitted in administrative buildings if purge and labyrinth sealing system are used to limit cross contamination to 0.04% of the exhaust air concentration by volume. The transfer media shall be coated with 3 angstrom molecular sieve desiccant. Silica gel desiccants allow significant cross contamination from exhaust to supply streams and are not permitted. Energy recovery wheels for laboratory system shall be evaluated based on programmatic use of the building, the analysis of the hazardous materials and chemicals planned to be used in the building, requirement of factory and field performance testing to verify allowable cross contamination limits.

10. It is encouraged to use actual laboratory equipment load data as described under 6.1.18 above for right sizing of equipment and improving energy efficiency.

11. The Project Officer shall be notified (with justification) when requirements of the energy conservation codes and standards cannot be satisfied due to program requirements. New construction or major renovation shall require complete HVAC and energy simulation modeling. Life cycle cost shall include capital cost factors for chillers and boilers as provided by NIH, as well as up to date energy costs.

Airflow control for Variable Air Volume (VAV) hoods must be integrated with the laboratory control system and its setting and operation must not jeopardize the safety and function of the laboratory.

Hydronic room cooling methods using chilled beams save considerable energy by reducing ventilation air, overall HVAC capacity and reheat energy. Appropriate dew point sensing and condensation monitoring methods shall be provided where chilled beams or other non-condensing hydronic cooling methods are used.

Run around coils are applied where supply and exhaust air handlers are separated by suitable distance. Energy recovery wheels have been problematic at NIH in regards to preventing cross contamination between the exhaust and intake air for laboratories and animal research facility.

6.1.13. HVAC System Design Requirements1. HVAC systems shall maintain a safe and comfortable working environment and be capable of adapting to new research initiatives. In addition, they shall be easy to maintain, energy efficient, and reliable to minimize lost research time.

2. HVAC systems for laboratories and animal facilities shall include central air-handling systems utilizing 100% outdoor air, which shall also provide adequate ventilation to offset exhaust air requirements. Laboratory and animal supply air shall not be recirculated or reused for other ventilation needs.


Laboratories and animal facilities at NIH involve hazardous materials, which could present significant risks to the occupants working labs. Laboratory and animal facility air shall not be recirculated to another space or facility in order to prevent migration of chemical fumes or airborne pathogens and/or to prevent the cross-contamination between laboratory spaces

Research frequently requires changes in operations and program and so HVAC systems for laboratory and animal facilities must be flexible and adaptable enough to allow for addition of heat producing equipment in labs or adding a fume hood in lab or adding additional ventilated cage racks in animal rooms. The A&E shall determine and document (in the Basis of Design) the degree of flexibility (adaptability) for the lab HVAC system based on discussions with the researchers and Project Officer.

Recirculation of laboratory air within the same space from devices such as fan coil units, induction units or chilled beams is acceptable.

For Tissue Culture Room, recirculation is not permitted where Fan Coil units and Induction units are located within the issue Culture Rooms) could potentially harbor bacteria that would impact the cells that are grown and used in Tissue Culture Rooms. Chilled beams are however acceptable in Tissue Culture Rooms since they tend to have better condensation control.

6.1.13.1. Design Requirements for Research Laboratory spaces1. HVAC systems for research laboratories shall be independent from other HVAC system

in the building. 2. N+1 redundancy – Central HVAC systems shall be provided with multiple air handling

units and exhaust fans to provide redundancy and improve reliability. These systems shall be designed to include manifolded air-handling units and exhaust fans to achieve N+1 redundancy and maintain operation at all times.

Research laboratories have different design criteria than other spaces in the building and

it becomes cost effective and safer to operate them independent of other systems in the building. Since research laboratories may conduct studies of long duration, which need to be performed under consistent environmental conditions in order to achieve repeatable results, the failure of the HVAC system is unacceptable. Redundancy reduces significant interruptions for repair and routine maintenance of the HVAC system.

6.1.13.2. Design Requirements for Animal Research Facilities1. HVAC systems for animal research facilities shall be independent from other building

HVAC systems. These systems s be capable of maintaining environmental conditions in any of the holding rooms for any of the species anticipated to be housed in the facility.

2. N+1 Redundancy – Central HVAC systems shall be provided with multiple air handling units and exhaust fans.to provide redundancy and reliability. These systems shall be designed to include manifolded air handling units and exhaust fans to achieve N+1 redundancy and maintain operations at all times .

3. HVAC for cage wash areas shall be provided with temperature control to minimize heat stress for occupants. In addition, exhaust hoods and dedicated ductwork shall be considered for space and the equipment.


4. HVAC for surgical facilities that are a support function of the Animal Research Facilities shall meet the requirements of the Institute of Laboratory Animal Resources (ILAR) "Guide for the Care and Use of Laboratory Animals" and the requirements defined for human surgical suites, which follow the Facility Guidelines Institute (FGI) standards. Ventilation shall however be 100% outside air.

5. HVAC for Magnetic Resonance Imaging (MRI), Computer Assisted Tomography (CT) and Positron emission Tomography (PET) to support animal surgery and non-surgery procedures require minimum ventilation of at least 6 Air changes per hour of 100% outside air. The room shall be negative relative to the surgery suites and animal facility. Rooms with MRI’s also require adequate ventilation for displacing the liquid cryogen that could accidently quench in the room during a breach

6. Some rooms may be designated as “Animal Isolation Cubicles” type rooms having a

housing chamber with sash fronts or hinged doors Uni-directional flow, laminar-flow type systems for any of these rooms may also be required.

Segregation prevents exposure of personnel to biological agents, allergens and odors. . Since most animal studies are of long duration, they shall be performed under consistent environmental conditions in order to achieve repeatable results. Thus, the failure of the HVAC system is unacceptable Redundancy reduces significant interruptions for repair and routine maintenance of the HVAC system.

Surgery areas provide support function for the Animal Research facility and cab be utilized for minor or major procedures with survival or non-survival outcomes. The procedures must be performed aseptically and suites typically include surgical support, animal preparation, scrub room, operating theater and post-operative recovery. Because of the potential biohazard associated with these animals, all ventilation air is 100% outside air. Imaging equipment such as MRI’s PET/CT scanners require stable room temperature and temperature and room temperature and stability is typically dictated by the manufacturer. There is potential of quenching of the magnets in the MRI rooms which could deplete the room of oxygen even when magnets are provided with their dedicated quench pipe to outdoors. For example, when it boils, each liter of liquid cryogen expands to approximately 700 liters of cryo gas Provisions must be made for having direct exhaust to outdoors.

6.1.14. Indoor Design ConditionsAll occupied spaces, unless noted otherwise, shall be designed to maintain the temperature and humidity levels as shown in Figure 4.

Figure 4. Indoor Design ConditionsIndoor Design Conditions

Season Temperature °C (°F) Relative Humidity %Summer 23 ± 1 (73 ± 2) 50 ± 5Winter 21 ± 1 (70 ± 2) 30 ± 5


1. Animal holding rooms shall be designed to meet the criteria stated in Figure 5 unless the research program requires more stringent temperature and humidity control.

port Areas2. Ideally, all animal-holding rooms shall be capable of housing all types of species. The

HVAC system shall also be capable of maintaining the full range of requirements for all anticipated animal populations. The temperature range required to accommodate most commonly used research animals is 18°C (65°F) to 29°C (84°F) controlled to plus or minus 1°C (2°F). The ranges do not represent acceptable fluctuation ranges. The humidity shall be between 30% and 70% and normally controlled to 50% plus or minus 5%. These ranges can be narrowed when the species anticipated have similar requirements.

3. Animal-holding areas shall be maintained at their specified design conditions at all times and under all load conditions. Indoor design conditions for various species are designated in Figure 5. Deviations from these indoor design conditions must be approved by the veterinarian in charge of the research program.

Figure 5. Indoor Design Conditions (Animal Holding Areas)Indoor Design Conditions

Species Temperature (1)°C (°F)

Relative Humidity %

Mouse 18 (65) – 26 (79) 35 ± 5 (3) (4)Hamster 18 (65) – 26 (79) 35 ± 5 (3),(4)Guinea Pig 18 (65) – 26 (79) 40 – 70Rabbit 16 (60) – 20 (68) 40 – 70Dog and Cat 16 (60) – 29 (84) 30 – 70Nonhuman Primate 16 (60) – 29 (84) 45 – 70Chicken 16 (60) – 27 (80) 45 – 70Amphibians Note 2 Note 2Aquatics (zebra fish) 26 (78) – 29 (84) 50 – 70Reptiles Note 2 Note 2Insects Note 2 Note 2door Design Conditions in Animal Housing FacilitiesNotes:(1) The A/E has the option of either designing for the full range listed in each animal species or, may after consultation with the facility users, choose a narrower range expected to meet present and all potential future requirements.(2) To be determined by the user. These space temperatures are research dependent.(3) Refer To: “Ventilation Design Handbook on animal research facilities using static Microisolators”; Volumes I and II, November 1998, Farhad Memarzadeh, PhD, P.E., NIH – Office of the Director, ORF Publication, Bethesda, MD.(4) Refer To: ASHRAE 2009 Fundamentals Handbook, Chapter 10 “Environmental Control For Animals and Plants”.

4. Some laboratories within the animal facility conduct special research requiring unique temperature and humidity ranges and control. These special cases shall be evaluated and provided for on a case-by-case basis. The HVAC system shall be designed to accommodate these unique conditions as they occur.

Outdoor Design Conditions


Animal research facilities require precise environmental control because variations and high temperatures can stress animals to the point that research would be compromised.

6.1.15. Ventilation Rates

Ventilation rates for other than laboratory and animal research laboratories shall be calculated based on outdoor air requirements in accordance with ASHRAE design guidelines and specific requirements based on manufacturer’s recommendation.

6.1.15.1. Ventilation Rates and Air Quality in Research Laboratories 1. Ventilation rate, for research laboratories, is typically driven by three factors: fume hood

demand, cooling loads, and removal of fumes and odors from the laboratory work area. The minimum outdoor air ventilation rate for laboratory space is 6 air-changes per hour, regardless of space cooling load. This minimum ventilation rate shall be maintained at all times. Some laboratories and support areas may require significantly higher ventilation rates to support fume hood demand or to cool dissipated heat from laboratory instruments and equipment.

2. Air Filtration – Air handling units to serve laboratory spaces shall be provided with filters upstream the supply air fans. When sizing fans, design shall be based on loaded filters. HEPA final filtration shall be provided in AHU to serve special laboratories where research materials are particularly susceptible to contamination from external sources. HEPA filtration of the supply air shall only be considered necessary for critical applications. The A/E shall confirm with NIH/DTR and NIH/DOHS for the need of HEPA filtration in laboratories.

Minimum ventilation rates provides protection to occupants from risk of hazardous materials, in the lab, from improper use of chemicals, accidental spill The ventilation rate does not include the dilution airflow required to deal with spills in a primary containment device (such as fume hood) . Some rooms with high hazard levels of materials may require higher than 6 air-changes per hour and A&E should consult with NIH/DOHS.

The use of chemical/hazardous sensors for reduction of the minimum ACH is not allowed at NIH facilities due to inability of the current sensors to sense all the toxic/hazardous materials in the air/and the need for frequent recalibration and replacement of these sensors.

6.1.15.2. Ventilation in Laboratories working with Laser EquipmentRooms where laser equipment is used shall be properly ventilated to avoid buildup of ozone generated from laser and mercury lamps.

6.1.15.3. Ventilation Systems and Air Quality in Animal Research Facilities1. Ventilation systems in animal research facilities shall be designed in consideration of

many factors such as:(a) Animal species and their population(b) Required minimum ventilation rate(c) Recommended ambient temperature and humidity(d) Heating and cooling loads within animal rooms Heat gain produced by animals (f) Use of microenvironments and the different

ventilation methods in animal cages


(g) Use of fume hoods and/or BSCs(h) Animal cage cleaning methods and type of beddings(i) Animal examinations method(j) Airborne contaminants(k) Institutional animal care standards, as applicable to animal facilities.

Allowable noise levels2. Ventilation rates, within each individual room, may vary depending on the actual animal species in each room. Figure 6 shows typical ventilation rates for various animal species.

Figure 6. Ventilation Rates in Animal Research FacilitiesVentilation rates in Animal Research Facilities (1)

Facilities Minimum Air Changes per Hour (2)Small Animal, Static Cage/Rack 15Small Animal, Ventilated Cage/Rack 10Large Animal 15Aquatics (zebra fish) 6Office / Administration Support 6 (3)Laboratories 6Imaging 6A Ventilation rates in Animal Research Facilities (1)Notes:(1) Ventilation rates refer to 100% outside air(2) Or higher to support fume hood and BSC demands and high heat loads(3) Only If they are integral part of the Animal research facility and the areas are served by 100% Outside Air units

3. Ventilation systems in animal research facilities shall meet the following requirements:(a) Rooms shall be designed to avoid drafts which could adversely affect animal health(b) Reduce airborne animal hair and particulate count(c) Minimum ventilation rate for animal housing and treatment facilities shall be in

accordance with ASHRAE HVAC Applications Handbook, chapter “Laboratories”, ASHRAE Fundamentals Handbook, chapter “Environmental Control for Animals and Plants”, and the Institute of Laboratory Animal Resources (ILAR) "Guide for the Care and Use of Laboratory Animals"

(d) Air re-circulation within animal facilities is prohibited.Air filtration - In addition to the typical pre-filtration and filtration normally used in air-handling units, final filtration is generally provided in air-handling units serving animal areas. This final filtration shall be located downstream from the supply fan to remove particulate and other contaminants, which can be generated within the air-handling equipment itself. Filter efficiency of final filters varies from 95% to 99.99% (HEPA). The Design Engineer shall review the specific Program of Requirements to establish specific filtration criteria.

6.1.16. Relative Room Pressurization6.1.16.1. Relative Room Pressurization within Laboratories

1. Laboratories shall be designed and air balanced so that air flows into the laboratory from adjacent (clean) spaces such as: offices, corridors, and non-laboratory spaces. In these facilities, the use of the once-through air-flow principle is based on: (1) Use of 100%


outdoor air to provide all the room air to be exhausted through laboratory spaces and laboratory containment equipment; (2) Size the exhaust air system to handle the simultaneous operation of all laboratory spaces and all laboratory containment equipment, and (3) Directing air flow from low hazard areas to high hazard areas at all times. Air supplied to the corridor and adjacent clean spaces shall be exhausted through the laboratory to achieve effective negative pressurization. The control of airflow direction, within research laboratory spaces, helps reduce the spread of odors, toxic chemicals, and air-borne contaminants as well as protect personnel from toxic and hazardous substances, and protect the integrity of experiments.

2. Laboratory spaces shall remain at a negative air pressure in relation to corridors and other non-laboratory spaces. Typically, these systems are designed to maintain 47 L/s (100 cfm) airflow from the corridor into each lab module. Administration areas in laboratory buildings shall always be positive with respect to corridors and laboratories. Supply air distribution for corridors shall be sized to offset transfer air to laboratories while maintaining an overall positive building pressure.

3. Amount of supply air flow to laboratory spaces shall meet the cooling loads and the exhaust air requirements. If the lab airflow is exhaust driven, the exhaust airflow requirements would exceed the cooling loads requirements. In this situation, the supply airflow would need to be increased to make up the difference between the cooling airflow and the required exhaust air flow. In cases where the cooling load airflow requirements exceed the required exhaust air rate requirements (cooling load driven), supplemental cooling units may be required if negative pressurization needs to be maintained to prohibit chemicals from migrating to other areas.

4. Special laboratories such as, genome DNA processing rooms, tissue culture laboratories, clean laboratories or sterile facilities etc., may require a different type of relative room pressurization. Some special laboratories may require positive air pressure in relation to adjacent spaces. In these cases, the use of a personnel entry or anterooms shall be used. These special applications need to be reviewed by NIH/DTR and NIH/DOHS.

6.1.16.2. Relative Room Pressurization Within Animal Facilities1. Relative pressurization within animal facilities is a series of complex relationships. Some

of these relationships may change as research and animal populations change. The HVAC system shall be capable of maintaining these relative pressure relationships and capable of adapting as facility utilization changes. In addition, animal spaces shall be protected against contamination from outside sources, including particulates brought in from outside by the HVAC airflow.

2. Relative pressurization between the corridor and the animal room depends on whether it is architecturally designed as single corridor or a dual corridor. In a dual corridor system there are separate clean and dirty corridors.

3. Animal rooms shall remain at a negative air pressure relative to clean corridors and other non-animal spaces. Clean areas of the facility including: the clean side of cage and rack washing, clean corridors, bedding dispensing, and feed preparation areas shall be positive to animal holding spaces and soiled areas. Soiled areas such as dirty service corridors, soiled side of cage and rack washing, and decontamination and waste-holding areas shall be maintained at a negative pressure.

3. Some areas have special pressurization requirements and shall be addressed individually by NIH/DTR and NIH/DOHS

4. Animal-holding areas for transgenic or immunosuppressed populations (also known as barrier facilities) shall be maintained at a positive pressure and may require special


filtration of supply air. When these rooms are maintained at positive pressure, an anteroom or similar feature shall be placed between the animal room and the corridor.

5. Potentially infectious populations shall be maintained at a negative pressure to prevent contamination of other animal populations. Depending on the nature of the infectious agents involved in the research, these areas may be required to meet the design criteria for biohazard containment facilities. The use of anterooms or micro-isolator housing units may be required to maintain these special conditions.

6. The pressure relationships for animal care areas including treatment rooms, procedure rooms, necropsy rooms, and surgical areas require investigation by the design team with the facility user to determine project-specific requirements. For surgery suites, the pressurization of the surgical suites is typically positive relative to the adjacent areas. The HVAC system shall be adaptable so that pressure relationships can be modified as required over the life of the facility. These applications need to be reviewed by NIH/DTR and NIH/DOHS. Dirty elevator shafts shall have negative air pressurization in relation to all surrounding areas.

Barrier facilities used for breeding and holding animals are designed to protect animals from infections from unwanted agents

6.1.17. Microenvironments1. Ventilation rates in animal facilities are typically 10 to 15 outdoor-air changes per hour

(ACH).2. For additional information, refer to ASHRAE, HVAC Applications handbook and to the

Institute of Laboratory Animal Resources, NRC, and Guide for the Care and Use of Laboratory Animals (ILAR).

3. System connections to microenvironments shall be designed to maintain manufacturer’s specified criteria.

4. For rooms housing animal ventilated racks, it is recommended, that the ventilation system be sized by adding the airflow required for the animal cooling/heating loads, of fully loaded ventilated racks, to the airflow required for other room cooling/heating loads such as lights, people, equipment, etc. This airflow shall be compared with the manufacturers recommended airflow and the larger airflow amount shall be used. The A/E shall evaluate all anticipated combinations of animals and cage systems; calculate supply air demands for make-up air, ventilation rates, cooling demand and heating demand; and design for whichever criteria results in the highest airflow demand. Go to http://orf.od.nih.gov/PoliciesAndGuidelines/Bioenvironmental/ for additional information and applicable studies, authored by Farhad Memarzadeh, Ph.D., P.E., of the National Institutes of Health, and refer to the following articles:(a) Comparison of Environment and Mice in Static and Mechanically Ventilated

Isolator Cages with Different Air Velocities and Ventilation Designs(b) Investigation of Static Microisolators in Wind Tunnel Tests and Validation of CFD

Cage Model(c) Mass Generation Rates of Ammonia, Moisture, and Heat Production in Mouse

Cages with Two Bedding Types, Two Mouse Strains, and Two Room Relative Humidities

(d) Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators - Volumes I and II

(e) Ventilation Design in Animal Research Facilities Using Static Microisolators

5. Ventilated cage racks may be equipped with fan/filter blowers on supply and exhaust. There are multiple configurations for coupling the racks to the building HVAC system. All direct connections from building exhaust to rack mounted exhaust


blower must be through thimble connection. Where ductwork serves multiple racks, balancing damper or pressure independent valve should be provided. A load simulator can also be provided to allow disconnecting of single rack from the system.

6. Multiple blowers in the room increase noise (each additional blower adds 3 dB to noise). A&E must consult with user where multiple blowers are in the same room, since some animals may be susceptible to the increased noise.

The practice of 10-15 ACH has also been used for secondary enclosures (animal cages/ microenvironments) and is considered to be an acceptable general practice. Although it is effective in many animal-housing settings, this practice does not take into account the range of possible heat loads; species, size and number of animals involved; type of bedding or frequency of cage-changing; the room dimensions; or the efficiency of air distribution from the secondary to the primary enclosure (animal room). In some situations, high flow rates may over ventilate a secondary enclosure that contains few animals and waste energy or by under ventilating, a secondary enclosure that contains many animals, which would allow heat and odor to accumulate.

Use of thimble connection on exhaust avoids the possibility of pressurizing the building exhaust system.

6.1.20. Air Distribution Systems1. Supply, exhaust, and outside air shall be ducted for all spaces, i.e., not taken through

ceiling plenums, shafts, mechanical equipment rooms, corridors, or furred spaces. The circulation of air directly between areas is not permitted, except into toilet rooms, locker rooms, and janitor’s closets. Circulation may also occur between adjacent corridors into a negative pressure area or out of positive pressure areas.

2. Supply air distribution system shall be designed to minimize turbulence and to avoid having an impact on the performance and function of primary containment equipment such as chemical fume hoods and BSCs.

(a) Air outlets shall not discharge into the face of fume hoods or BSCs. The cross draft velocity near (at 2 feet distance) the face of the fume hood or BSC shall not be greater than 50 FPM at 5 feet AFF.

High velocities and drafts at the face of the hood or BSC can create eddies near the face of the hood or cabinet and cause the air to leak out of the cabinet and cause the hoods to fail the field test

(b) Exhaust grilles and registers shall be located away from supply air diffusers in a manner that creates uniform, low velocity airflow across the room.

3. Plenums and air shafts for distribution of supply or exhaust air is prohibited in NIH laboratories and non-laboratory buildings. Common outdoor air ductwork may be permitted for outdoor air intakes to multiple air-handling units due to space constraints and building configuration.This is to limit the potential for cross-contamination of airstreams.

4. Corridors shall be provided with conditioned air. The quantity of conditioned air to the corridors shall be sufficient to maintain an overall positive building pressure.Providing conditioned air to the corridors helps to maintain design temperatures and as required to make up air for negatively pressurized rooms opening directly to the corridor.


6.1.20.1. Laboratory Air DistributionLaboratory spaces shall be designed with special attention to air quality, room acoustics, supply air temperature, supply air humidity, airflow quantities, air velocity, and air diffusion and distribution within the space. In addition, space air distribution shall meet the following requirements:

1. Distribution shall prevent cross contamination between individual spaces, air shall flow from areas of least contamination to areas of higher contamination potential, i.e., from "clean" to "dirty" areas.

2. Air supply devices shall be located at ceiling level or close to ceiling level if located on sidewalls. Air distribution and diffusion devices shall be selected to minimize temperature gradients and air turbulence.

3. Supply air devices shall be located away from fume hoods and BScs Large quantities of supply air can best be delivered through perforated plate air outlets or diffusers designed for large air volumes.

4. Space temperature and humidity shall be consistent in each individual room. Space temperature shall be monitored in each individual room.

5. Each lab space shall be provided with dedicated temperature controls. This shall include the dedicated air-terminal units for the supply and exhaust air.

6.1.20.2. Animal Room Air Distribution1. Animal facilities shall be designed with special attention to air quality, room acoustics,

supply air temperature, supply air humidity, airflow quantities, air velocity, and air diffusion and distribution within the space. In addition, space air distribution shall meet the following requirements:(a) Distribution shall prevent cross contamination between individual spaces, air

shall flow from areas of least contamination to areas of higher contamination potential, i.e., from "clean" to "dirty" areas.

(b) Air supply devices shall be located at ceiling level or close to ceiling level if located on sidewalls. Air distribution and diffusion devices shall be selected to minimize temperature differentials in the space.

(c) The A/E shall ensure that the system does not create drafts on the animals and that the airflow is uniform in nature.

(d) Where required, a provision shall also be made for high exhaust to be activated for directly exhausted racks to maximize space flexibility.

(e) Individual room temperature sensors, for animal holding rooms, shall be located inside the general exhaust ductwork from each room at an accessible location near the room envelope.

(f) Space temperature and humidity shall be consistent in each individual room. Space temperature shall be monitored and recorded in each individual room.

(g) Exposed HVAC ductwork is generally not recommended in animal rooms. If constructed, it shall be 316 SS to allow facilitate cleaning.

2. Go to http://orf.od.nih.gov/PoliciesAndGuidelines/Bioenvironmental/ for additional

information and an applicable study, authored by Farhad Memarzadeh, Ph.D., P.E., of the National Institutes of Health, and refer to the following article:(a) Analysis of Air Supply Type and Exhaust Location in Laboratory Animal

Research Facilities Using CFD

6.1.21. Anterooms


1. Anterooms are typically located between the laboratory/isolation/protected room and the corridor. The anteroom has two sets of doors, one door to the laboratory/isolation/protected room and one door to the corridor. These two doors are interlocked so that only one door can be opened at a time. Depending on the type of isolation required, the anteroom may be positive, negative or neutral. The use and type of anterooms shall be reviewed with NIH/DTR and NIH/DOHS.

2. Anterooms shall be provided with both supply and exhaust air grilles. In addition, anterooms shall be provided with dedicated supply and exhaust air terminal units/boxes.This permits the reconfiguration of the anteroom to accommodate program changes.

3. Room differential pressure sensors shall be provided to monitor the pressure differential between the anteroom, the laboratory/isolation/protected room and the corridor. Room pressure differential is set to maintain a minimum of 2.5 Pa (0.01 in w.g.). In some cases, room differential pressures may be as high as 12.5 Pa (0.05 in w.g.) or greater. Required room differential pressure shall be reviewed by NIH/DTR and NIH/DOHS. See BAS section for further requirements.

6.1.22. Program Equipment1. The selection and use of program equipment such as microscopes, imaging systems,

NMRs, refrigerators, freezers, centrifuges, autoclaves, glassware washers, BSCs, fume hoods, etc. shall be established early in the design phase.This is to allow mechanical and electrical systems to be designed to support specific equipment requirements.

2. Program equipment shall comply with NFPA, OSHA, ANSI, NSF, NIH Fume Hoods Specifications requirements and other applicable standards. Equipment selected shall not contain asbestos, lead or mercury.

3. The A/E shall obtain equipment requirements so that heat rejection, electrical usage, operation usage, and other utility consumption data are included in the design of the HVAC systems. Equipment space requirements shall be closely reviewed, and layouts shall allow for access to all piping, wiring, and ductwork connections, easy cleaning, maintenance and repairs.

4. Mechanical systems shall be designed and detailed so that they do not induce harm to or impede the operating efficiency of program equipment. Pressure regulators, safety relief valves, gravity drainage facilities, temperature controls, and backflow protection devices shall be provided for safe operation.

5. The building temperature control systems / Building Automation Systems (BAS) shall not be used to operate/control program equipment. The complete control and operation/maintenance strategy for program equipment shall be closely reviewed against program requirements and with program users.

6.1.22.1. Flammable Storage CabinetsFlammable storage cabinets shall not be vented and shall not be located underneath fume hoods.Flammable storage cabinets are tested unvented. Unless the manufacturer’s specific venting equipment is used, the safety of the cabinet can easily be compromised.

6.1.22.2. Corrosive Storage CabinetsA ventilated corrosive storage cabinet shall be provided in each laboratory. Typically, these are located underneath fume hoods if present.

6.1.22.3 Biological Safety Cabinets


1. At NIH, biological safety cabinets (BSC) are typically Class II, Type A1 or Type A2 (recirculated), which shall NOT be hard ducted to the building exhaust air system, nor shall thimble connections be used.

This is an NIH DOHS requirement.2. BSC Class I, Class II-B1 (partially exhausted) and Class II-B2 (fully exhausted) are also

used in NIH facilities. These particular types of BSCs shall be hard ducted to a dedicated building exhaust air system. In addition, BSC Class II-B1 and Class II-B2 shall be factory provided with means of shutting down the BSCs internal fan, whenever the static pressure, in the building exhaust air system connected to the BSC, drops below the required set point. Building exhaust air systems serving these BSCs shall include provisions for increasing the systems static pressure to compensate for loading of the exhaust HEPA filters within the BSC, i.e. VFDs.This is required to avoid having a positive BSC and positive exhaust ductwork. This will prevent the release of hazardous products into the laboratory space. Whenever multiple BSC of this type are connected to the same system, each BSC shall be provided with a dedicated exhaust type air terminal unit. This will ensure the proper exhaust air amount is maintained through each BSC Exhaust HEPA’s in BSC’s require the exhaust system to maintain up to 2.5” w.g. SP at the inlet of the ducted BSC’s.

3. Rooms with ducted BSCs shall be provided with an additional room exhaust air grille connected to a dedicated exhaust air terminal unit.

Whenever the manual isolation damper associated with the BSC is closed, during the certification process of the BSC, the room ventilation system shall be automatically or manually adjusted in order to maintain the negative pressure in the laboratory.

4. Regardless of class and type, all BSCs at NIH, shall be provided with unit mounted HEPA filtration of the exhaust air prior to its discharge to the room space or to the outdoors. All Class II BSCs shall comply with Standard NSF-49 developed by the National Sanitation Foundation (NSF).

5. Projects requiring the use of BSCs, regardless of class or type, shall be reviewed and approved by the NIH/DOHS and NIH/DTR during the design phase of the project.

6.1.22.4. Fume Hoods1. Fume hoods may be variable air volume (VAV) or constant air volume (CV) type.

Although the use of VAV hoods is highly recommended, the decision shall be based on a comprehensive lifecycle cost analysis that accounts for all system features required by NIH and taking into account existing building limitations. Fume hoods to be used in NIH facilities must meet the criteria as shown in Figure 7. Constant Volume Fume hoods are typically “Bypass” type

Figure 7. Fume Hood DesignationsFume Hood Types

Fume Hood Type Nominal Hood Widthmm (in.)

NIH Specification Section

Vertical Sash Bench 1200 (48) – 1800 (72) 11810 (August 2004)Horizontal Sash Bench 1800 (72) 11820 (August 2004)Combination Sash Bench 1800 (72) 11830 (August 2004)Outdoor Design Conditions

2. Fume hoods shall comply with the testing requirements in the following NIH documents:


(a) NIH Specification Section 15991 – On Site Testing – Constant Volume Fume Hoods

(b) NIH Specification Section 15992 – On Site Testing – VAV Fume Hoods(c) Appendix E.3 “Fume Hood Testing and Alarm System.”

3. Fume hoods shall be evaluated “AM” (as manufactured) under the ANSI/ASHRAE STD 110 and shall meet the following minimum performance ratings:(a) Sash design position or positions: 457 mm (18 in.)(b) Average face velocity: 0.51 m/s (100 fpm) (plus or minus 10%)(c) Range of face velocities: No point in grid below 0.41 m/s (80 fpm) or above 0.61

m/s (120 fpm). Actual not as measured.(d) Average face velocity for sash at 50%: 0.41 (80) to 0.76 m/s (150 fpm)(e) Average face velocity for sash at 25%: 0.41 (80) to 1.52 m/s (300 fpm)(f) Performance rating: 0.05 ppm(g) Sash movement performance rating: 0.10 ppm(h) Response time for VAV hoods: Less than 3 seconds(i) Percentage of auxiliary air supply: 0% (auxiliary air hoods are not allowed)(j) Static pressure loss: Not more than 124 Pa (0.5 in. w.g.) at 0.51 m/s (100 fpm)

face velocity.

6.1.22.5. Variable Air Volume Fume Hoods1. VAV fume hoods to be used in NIH facilities shall be of the restricted bypass type and

shall meet the following requirements:(a) Fume hoods shall meet current NIH fume hood specifications.(b) Fume hoods in non-containment type laboratories shall have no air-cleaning

(HEPA or charcoal), except for radiological hoods.(c) The laboratory shall remain under negative pressure with respect to the corridor

or adjoining rooms even when the fume hood operates at the minimum exhaust air rate. When the exhaust air quantity is reduced, supply air quantity shall be reduced by the same volume.

(d) Laboratory minimum ventilation requirement, ACH, shall be provided even when the fume hood(s) operate in the minimum exhaust air rate position.

(e) Airflow monitoring/alarm devices shall be installed at each fume hood to provide the user with operating information. These devices shall monitor the following: (1) face velocity at the sash opening, (2) Sash position, and (3) pressure differential between hood and room.

(f) VAV hood sash shall not be operated automatically based on the proximity sensors.

2. Go to http://orf.od.nih.gov/PoliciesAndGuidelines/Bioenvironmental/ for additional information and applicable studies authored by Farhad Memarzadeh, Ph.D., P.E., of the National Institutes of Health and refer to the following articles:(a) Methodology for Optimization of Laboratory Hood Containment - Volumes I and II(b) NIH - Section 15991 - Onsite Testing for Constant Volume Fume Hoods - June

2006(c) NIH - Section 15992 - Onsite Testing for Variable Volume Fume Hoods - June

2006

6.1.22.6. Low Flow, Auxiliary Air, Radioisotope and Perchloric Acid Fume Hoods 1. Low flow fume hoods may be used at NIH as long as they meet ALL the requirements

as outlined in the NIH / ASHRAE 110 Modified Fume Hood Testing Protocol. In addition, fume hoods shall comply with the testing requirements of the listed NIH onsite testing specification sections 15991, 15992 and Appendix E. 3 “Fume Hood Testing and Alarm


System.” The face velocity of low flow hoods should NEVER be below 0.41 m/s (80 fpm).

2. Auxiliary air-type fume hoods shall NOT be used in any NIH facilities. In the event of a retrofit application, the A/E shall investigate the capacities of the existing system exclusive of the auxiliary air, and laboratory supply and exhaust system characteristics. Once it has been established that the system can support the addition or replacement of an existing fume hood, this information shall be forwarded to the project officer for approval before the design is allowed to proceed.Auxiliary air systems use more energy than they are intended to save. They also impact the laboratory HVAC system’s ability to maintain stable temperature and humidity set points.

3. Radioisotope hoods may be used with research using radioactive isotopes. The hoods are designed with internal surfaces impermeable to radioactive materials and strong to support lead shielding. Ductwork shall facilitate decontamination. HEPA and/or charcoal filters may be needed in exhaust duct. Consult with NIH DOHS. .

4. Perchloric Acid hoods use extremely oxidizing agents that form vapors that could cause potential explosion hazard. Exhaust system shall be equipped with water wash down and drainage system. Ductwork shall be welded 316 stainless steel.

6.1.23. Environmental Rooms1. Environmental rooms could be constant temperature cold rooms or hot rooms. These

rooms shall be located to accommodate service from outside the room space. Temperature and humidity readouts shall be located inside and outside the room. Ventilation of environmental rooms, such as cold rooms, which serve as occupied functioning laboratory spaces, shall be designed in accordance to the latest issue of ASHRAE Standard 62. Environmental rooms used primarily for storage functions shall not require ducted ventilation air.

2. Cold rooms shall be provided with remote condensing units, which are not located directly above the room. Floor mounted condensing units are preferred. Associated, air conditioning components shall be located to accommodate service from outside the room. Condensing units shall be water cooled. If air cooled condensing units are used due to the lack of hydronic cooling media, then, the temperature of the area surrounding the condenser shall not be allowed to exceed 6°C (10°F) above the temperature of occupied adjacent areas. Design consideration shall be given to ventilating and dissipating heat accumulation caused by equipment condensers.

6.1.24. Equipment Room Ventilation (Non-Lab Equipment Rooms)1. Equipment rooms such as mechanical, electrical, boiler, chillers, pumps, air-handling

units, fans, autoclave, and cage wash equipment, etc. shall be heated, ventilated and conditioned as follows:(a) Heating shall be provided by the use of steam or heating water. These rooms

shall be heated to maintain a space temperature of 18°C (65°F). (c) Minimum ventilation rates shall comply with local building codes and good Indoor

air quality practices and requirements.(d) Containment exhaust systems shall not be used to ventilate mechanical spaces.

(f) It is recommended to locate the sensitive equipment, such as vacuum pumps, air compressors, pure water production, etc., shall be located in a dedicated room where the temperature is to be maintain between 18°C (65°F) and 26°C (80°F). If dedicated room is not feasible, localized cooling shall be provided.


2. Mechanical room shall be maintained between 18°C (65°F) and 31°C (90°F).2.. Ventilation systems shall be provided to maintain the space temperature to no more than 12°C (20°F) above outdoor air temperature for the boiler room, cage wash / autoclave service areas, transformer vault, and steam rooms.

2. Electrical rooms (except transformer vault) shall be conditioned and /or ventilated to maintain a space temperature no more than 26°C (80°F). Outdoor air into this room shall be filtered by using filters of MERV 8 based on ASHRAE’s Standard 52, atmospheric dust-spot test efficiency.

3. Secondary switchgear rooms shall be provided with heating and cooling equipment to maintain space temperature between 18°C (65°F) and 26°C (80°F) and humidity level below condensing to protect switchgear and electronic controls. Switchgear/transformer rooms located at the NIH Bethesda and Poolesville campuses shall be provided with temperature and humidity sensors. These sensors shall be connected to the existing Supervisory Control and Data Acquisition (SCADA) system, which is the energy monitoring system for the campus.

4. Hydronic piping shall not be located within electrical rooms and secondary switchgear rooms. In the event that this cannot be avoided, protection shall be added such as drip pans beneath all piping and equipment. These drip pans shall be provided with water detection alarms connected to the BAS. Hydronic piping and drip pans shall never be located over any electrical transformer, electrical panels, and switchgear.

5. Large equipment rooms, with significant ventilation requirements, shall be provided with multiple fans.To avoid having areas with excessive accumulated heat.

6. Boiler rooms and rooms with combustion equipment shall be provided with a ventilation system that combines the ventilation requirements and the combustion air requirements.

7. Elevator machine rooms, telecommunication closets, fire alarm rooms, and other similar spaces with electronic equipment shall be provided with air conditioning served from emergency power source. The A/E shall define criteria for these spaces and design accordingly.

8. Ventilation of storage closets for cylinders of compressed gases shall be designed per NFPA 55, building and local codes. Ventilation air is typically exhausted from closet and makeup air can be introduced from surrounding air. Exhaust fan serving this space is served from emergency standby power. Closets containing materials with explosion potential shall be carefully designed with all safety considerations. NFPA 68 is the reference standard for explosion venting.

6.1.25. Mechanical Equipment Location and AccessMechanical systems shall be designed in accordance with the following principles:

1. HVAC, electrical, and plumbing systems shall be zoned to avoid overlapping of multiple systems over multiple buildings zones.This will help reduce building complexity during shutdowns, building trouble shutting and building renovation.

2. HVAC systems shall be designed such that there are specific building zones for smoke and fire control, piping, ductwork, conduits, cable trays, and lighting. This is to include defined access and service areas/zones to all equipment. These areas/zones need to be identified in the construction documents. This needs to be particularly defined in mechanical rooms and interstitial spaces.

3. Systems shall be selected to minimize the number mechanical components requiring service and maintenance.


4. System components requiring frequent service and maintenance shall be located in equipment rooms or service areas and not above suspended ceilings or in occupied spaces.

5. Clear and safe access shall be provided for servicing, removing, and replacing equipment.

6. Sufficient instrumentation shall be specified for monitoring, measuring, adjusting, controlling, and operating at part load as well as full load. See BAS section for detailed requirements.

7. Equipment shall be selected and located for long-term durability, reliability, maintainability, and serviceability, so as to meet, at a minimum, the service life expectancy indicated by ASHRAE.

8. Equipment shall not be located in confined, or with an access through, secured spaces.

6.1.18. Heating SystemsHeating, in NIH facilities, shall be provided by the use of steam and/or heating water systems. Electric resistance heating shall NOT be used to provide heating. This includes built-in small electric heaters. The exceptions are:

5. Steam is not available;6. Generator / switch gear rooms are acceptable to use electric heat.

6.1.19. Cooling SystemsCooling, in NIH facilities, shall be provided by the use of chilled water/hydronic systems. The use of air-cooled, self-contained refrigeration systems for building cooling coils in air handling systems shall not be permitted unless chilled water is not available within close proximity or redundancy is required for mission critical rooms.

6.1.26. Exhaust Air SystemsEvery exhaust air system is unique and requires specific review of issues such as air quantity, filtration, construction materials, type of discharge, controls, emergency power, hours of operation, etc. In addition, exhaust air systems shall meet the following requirements:

1. General exhaust should follow requirements in ASHRAE 62.1.? 2. Exhaust air systems shall be designed to operate 24 hours per day, 7 days a week.3. Exhaust air systems shall be balanced with the AHU supply air systems.4. Capacity of exhaust air systems shall be increased by 20%.

To allow for future expansion.5. Electric motors and drives, associated with exhaust fans, shall be located out of the

exhaust air stream.6. Electrical motors associated with exhaust fans shall be upsized by one motor size.7. Emergency Power - Exhaust air fans and systems shall be connected to the emergency

electrical power system.8. Comply with NFPA 90A. Exhaust air ductwork shall not be located in the same shaft with

supply air ductwork and return air ductwork.9. Positive pressurized exhaust air ductwork should be avoided. No positive pressurized

ductwork segment, of any laboratory exhaust air system, shall be located in any occupied zone, including mechanical rooms. All flex connections on the discharge of the exhaust fan shall be of the type, size and capacity to match the estimated maximum developed static pressure...Any duct leakage of pressurized exhaust ductwork would pose a contamination hazard.

10. Fume hood exhaust ductwork and exhaust fans shall be constructed of corrosion resistant material, such as stainless steel, or be coated with a protective corrosion


resistant product such as epoxy phenolic, or vinyl selected to resist the anticipated corrosive fumes.

11. When combining containment type equipment into a single exhaust air system, the A/E shall obtain approval from NIH/DOHS for exhaust air compatibility.

12. Exhaust air discharge and stack shall be as per section 6-2, paragraph 6.2.4 “Location of Outdoor Air Intake and Exhaust Discharge” at a minimum. Air entrainment study (wind wake analysis) may be required which may increase these minimum requirements.

13. Dampers – Smoke dampers and/or fire dampers shall NOT be installed in laboratory exhaust ducts serving fume hoods, BSCs, or other containment type equipment.

14. Controls - Variable and constant air volume exhaust air fans serving multiple spaces shall be equipped with VFDs, where applicable, for control of air flow and duct static pressure. Exhaust air from each laboratory and animal holding/support area shall be controlled by a dedicated pressure-independent air terminal air unit.

15. Snorkel exhaust systems used for (Local Exhaust Vents) LEV and also for heat extraction from heat-producing equipment may be tied to the general exhaust system.

16. Where multiple VAV fume hoods are manifolded to a single system, the A&E may reduce the equipment capacities of the exhaust system. This is based on the usage factors of the VAV hoods and should be evaluated on a case by case basis in conjunction with the user and DOHS

All exhaust devices are seldom used simultaneously at full capacity and there is potential to save capital and energy cost by reducing the size of the exhaust system

6.1.26.1. Dedicated Exhaust Air SystemsResearch areas shall be provided with dedicated and separate exhaust air systems from non-research functions in the building. In addition, the following systems shall be provided with dedicated and separate/independent exhaust air systems from any other exhaust air systems in the building:

1. Isolation rooms. Multiple isolation rooms may be combined into a single exhaust air system

2. Laboratory general research areas3. Fume hood exhaust. However, fume hood exhaust may be combined with laboratory

general research exhaust but only after penetrating the last fire rated partition on the floor. The alternate to this approach would be to terminate within the shaft by the use of sub-duct assembly.

4. Ducted BSCs5. Radioisotope/radioactive fume hoods6. Perchloric Acid hoods7. Animal general research areas8. Cage washers. In addition, certain cage wash equipment may require special space

configuration. The A/E shall discuss these systems with the animal program personnel.9. Ductwork serving central sterilization processing areas10. Ductwork serving areas with EtO sterilizers. EtO exhaust air systems shall meet the

installation requirements set forth by USEPA. This system shall be provided with means of determining a failure of the exhaust air system and shutting down the EtO sterilizer.

11. Ductwork serving spaces with battery-charging equipment12. Ductwork serving gas cylinders storage spaces.13. Toilet exhaust air systems. This is to include janitor’s closets and locker rooms14. Any other function as designated by NIH/DOHS15. NMR purge and quench


Advantages of having ducted BSC’s on independent exhaust system does not require the entire exhaust system to be designed to the minimum pressure requirements for the ducted BSC’s and allows the BSC’s to operate without being subjected to frequent out of range alarms.

6.1.26.2. Exhaust Air Systems1. Animal room exhaust shall be filtered at the room exhaust grille with a rough filter to

capture hair and dander. This is to be accomplished by providing air filter tracks in the face of the room exhaust air grille. Filters shall be 25 mm (1-in.) throwaway type. Whenever feasible, exhaust air grilles with face mounted air filters shall be located at 300 mm (12-in.) above finished floor.

2. Exhaust air from animal rooms shall be discharged outdoors without recirculation into any other room. For protection of personnel and to minimize the potential for cross contamination of animals, the direction of airflow shall be inward to the animal rooms, at all times. Where protection of the animals from possible contamination is required, consideration should be made of providing ventilated airlocks for the animal rooms. The use of filtered isolation cages may also be considered. Architect/Engineers should consult with animal facility personnel with regard to the specific requirements for protection of animals.

3. In cage wash facilities, the “dirty,” “clean,” and cage washing equipment, including associated mechanical supporting equipment area, shall be physically separated from each other, including equipment pits.

6.1.26.3. Necropsy and Pathology workNecropsy and pathology work with infectious agents in animal research facilities shall be done within BSCs or on downdraft tables. The use and the design of downdraft tables shall be approved by NIH/DOHS. Downdraft tables shall provide an average downdraft of 0.25 m/s (50 fpm) at a height of 125 mm (5 in.) over the entire top surface of the table. [For detailed calculations on downdraft table particle capture efficiency –See Appendix H]

6.1.26.4. RedundancyExhaust air systems shall be arranged with multiple manifolded fans designed to achieve N+1 redundancy and maintain the exhaust air system fully operational, at all times. Each manifolded fan shall be designed to be fully isolated while the overall system remains fully operational. In the case of single fan systems, in addition to the main fan, a standby fan shall be provided. The A/E shall review redundancy requirements for each particular system with the program user and the NIH/DOHS. Regardless of the system size, exhaust systems serving the following spaces and/or equipment shall be provided with an N+1 redundancy:

1. Isolation rooms2. Laboratory general research areas3. Fume hood exhaust4. Radioisotope/radioactive fume hoods5. Animal general research areas6. Cage washers7. Any other function as designated by NIH/DOHS8. BSCs

6.1.26.5. Isolation RoomsExhaust air system for isolation rooms shall be a dedicated system capable of serving negative pressure (normal isolation) rooms or positive pressure (reverse isolation) rooms. Exhaust air systems for isolation rooms dealing with highly infectious pathogens may require bag-in/bag-out


HEPA filtration. The A/E shall review filtration requirements for each particular system with the program user and the NIH/DOHS. If HEPA filtration is not required, the system shall be designed with provisions for adding the HEPA filtration in the future. This dedicated exhaust air system shall include: pressure-independent constant-volume air terminal units, roof-mounted exhaust fans, VFD for filter loading and/or for multiple rooms applications, exhaust stacks, bag-in/bag-out HEPA filters, etc.

6.1.26.6. Exhaust Air FiltrationGenerally, exhaust air does not require filtration or scrubbing. However, in special laboratories, such as laboratories using radioisotopes or certain hazardous chemicals, the exhaust air may require special filtration before being discharged to the outdoors. The A/E shall consult with NIH/DTR, NIH/DOHS, and NIH/ Radiation Safety Branch for specific requirements. These exhaust air systems shall include provisions for accounting for filter loading and adjusting the system static pressure in order to maintain the required air flow amount. Whenever filters or scrubbers are required, they shall be located as close to the source of contamination as possible while maintaining ready access for installation, monitoring, maintenance, testing, and filter replacement.

6.1.26.7. Wet Exhaust1. Wet exhaust air from areas such as sterilizers, autoclaves, glass washers, cage

washers, and pot-washing equipment, etc., shall be captured by using canopy-type stainless steel hoods at each equipment entrance and exit. Canopy hoods shall meet the following requirements:(a) The canopy hood shall be located above the door to load and unload the equipment.

In the case of double sided equipment, a canopy shall be placed above each equipment door.

(b) Exhaust air shall be at a minimum rate of 0.254 m/s (50 fpm) capture velocity at the face of the canopy hood.

(c) Canopy hood design shall include a drip ledge to collect condensate steam. In large canopy hoods, collected condensate steam shall be piped to the nearest floor drain.

(d) Wet exhaust systems shall be separated from other exhaust air systems.(e) Ductwork shall be pitched back toward the canopy hood. Provide duct drains and/or

drip legs for low points in ductwork and exhaust risers.(f) Canopy exhaust hoods shall be installed above steam vapor and heat generating

equipment in both the “dirty” and the “clean” sides of the equipment.2. For additional information refer to Appendix E.5 “Calculation Protocols for Canopy

Hoods over Autoclaves: NIH Local Exhaust Ventilation (LEV) test Protocol.”

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