AIHA Guideline 2 2004Recommendations for the Management,Operation, Testing, and Maintenance ofHVAC Systems: Maintaining AcceptableIndoor Air Quality in NonindustrialEmployee Occupancies Through DilutionVentilationApproval date: 03/09/2004American Industrial Hygiene AssociationAbout this DocumentAIHA guidelines are developed through a consensus process that involves review by internal AIHA technical committees and external review by outside experts. Through thisprocess, AIHA brings together volunteers with varied backgrounds and viewpoints. The intent of this document is to provide practical guidance to the practicing OEHS professional. This document is not a standard. DisclaimerAIHA did not independently test the methods or verify the accuracy of recommendationscontained in this document. Specific mention of manufacturers and products in this bookdoes not represent an endorsement by AIHA.CopyrightCopyright 2004 by the American Industrial Hygiene Association. All rights reserved. No part of this publication may be reproduced in any form, by photostat, microfilm,retrieval system, or any other means, without prior permission from the publisher.American Industrial Hygiene Association2700 Prosperity Avenue, Suite 250Fairfax, VA 22031(703) 849-8888www.aiha.orgStock #: IVEG04-658ISBN #: 1-931504-52-0Printed in the United States of AmericaTable of ContentsForward......................................................................................................................vii1. Scope......................................................................................................................12.Related Standards, Guidelines, and Publications ......................................................23.Definitions...............................................................................................................24.General Guidance...................................................................................................75.Management of HVAC Systems Used for Dilution ....................................................96.HVAC System Equipment .......................................................................................127.Outdoor Air ..........................................................................................................198.Operation and Maintenance..................................................................................269. Inspection, Monitoring, Testing, Balancing, and Operational Checks ......................29Appendix A: Supplementary Information.....................................................................33Appendix B: Audit Form..............................................................................................431Explanation and Information1. Scope1.1 Properly operating HVAC systems are used to maintain and promote comfortable andhealthful indoor air conditions in the non-industrial occupational work environmentthrough dilution and removal of aircontaminants.The committee recognizes that the Guidelinemay need to be modified so as to apply toolder HVAC equipment, for example, inductionand fan-coil units.1.2 Exclusions. ASHRAE and other standards/codes-setting organizations provide standardsand guidelines for the design and constructionof new HVAC facilities.ANSI Z9 and AIHA have published standardsrelated to the ventilation of industrial occu-pancies. See Section 2 and the AIHA web site:www.aiha.org. Other standards and guidelinescovering HVAC systems are found in Appendix A2.Industrial-occupancy dilution ventilation systemswill be covered in a future ANSI Z9 standard.LEV systems are covered in ANSI Z9.2. Labventilation systems are covered in ANSI Z9.5.Many nonoccupancy buildings use exhaustsystems in bathrooms, kitchens, copy rooms,and so forth. These exhaust systems are notconsidered LEV systems in the Guideline.Displacement and plug-flow ventilationsystems may not be dilution-based controls.When these systems are consideredenhanced dilution systems, recommenda-tions of the Guideline can be useful.Other occupational stressor locations mightinclude oil vapors in kitchens, TB germs inhospitals, perchloroethylene in dry cleaningestablishments, and acetic acid in photodevelopment shops. These occupancies arebetter handled using traditional industrialhygiene ventilation principles and practices.Naturally ventilated buildings may includewarehouses, older office buildings in mildclimates, and so forth.Guideline Administrative Statements1. Scope1.1 Scope. The Guideline provides suggestionsandrecommendations for the management,operation, maintenance, and testing ofheating, ventilation, and air conditioning(HVAC) systems used for dilution ventilation toprovide acceptable air quality in nonindustrialemployee occupancies.1.2 Exclusions. The Guideline does not cover thefollowing. Design and construction of HVAC systems Ventilation of laboratories Dilution ventilation systems used inindustrial employee occupancies Local exhaust ventilation (LEV) systems usedfor industrial process control HVAC systems based exclusively ondisplacement or plug-flow ventilationapproaches Hospitals and other commercial facilitiesthat introduce unusual occupationalstressors into the air such as kitchens, photodevelopment labs, dry cleaners, and so forth Exclusively naturally ventilated buildings2. Related Standards, Guidelines and PublicationsExisting standards, guidelines, and othersources of information contain provisions thatcomplement the recommendations of thisGuideline. Please see Appendix A2 for a list ofsuch documents.3. Definitions3.1 Acceptable Concentration. The concentration inair of a gas, vapor, or aerosol that the userdetermines is acceptable for the occupiedspace.3.2Air Cleaning Equipment. A device orcombination of devices for removing orreducing contaminants from the air handler by an HVAC system.3.3 AHU; Air-Handling Unit. Those components ofthe HVAC system that power and movecirculating air.22. Related Standards, Guidelines and PublicationsThe list in Appendix A2 is not all-inclusive butcontains items considered part of the body ofcurrent and recognized standards of goodpractice. All codes, regulations, standards,guidelines, and publications are subject torevision. Users of the Guideline areencouraged to consult the most recent editionsof the codes, regulations, standards,guidelines, and other publications listed.3. DefinitionsDefinitions explain major and repeating termsas they are used in the Guideline. Not allterms in the Guideline are defined withexactness, for example, experienced andappropriately dry, because the definitionmay vary with the time, the equipment, usage,and so forth. Indeed, many recommendationsare purposely left undefined to assureflexibility for the user. The user may find ithelpful to obtain the services of a cognizantauthority to assist in the definition of terms,conditions, and recommendations not readilyunderstood.3.1User-defined acceptable concentrations mightinclude, for example, carbon dioxide at orbelow 700+ background ppm,,nondetectable odor level, x% of the OSHAPEL, and so forth. This definition is not inconflict with the ASHRAE 622001 definition ofacceptable air: Air in which there are noknown contaminants at harmful or irritatingconcentrations as determined by cognizantauthorities (e.g., toxicologists, industrialhygienists, or other appropriate professionals).3.2 Typically only particle filters are used in HVACsystems, but some may provide chemical andactivated charcoal filters for gases and vapors.Air-cleaning equipment may be specified toprotect air-handling equipment only, or maybe specified to protect occupants as well.3.3 Typically includes mixing plenum, filters,heating and cooling coils, and fans. (Seedescriptive Figure A3.3 in the appendix.)2. Related Standards, Guidelines and PublicationsExisting standards, guidelines, and othersources of information contain provisions thatcomplement the recommendations of thisGuideline. Please see Appendix A2 for a list ofsuch documents.3. Definitions3.1 Acceptable Concentration. The concentration inair of a gas, vapor, or aerosol that the userdetermines is acceptable for the occupiedspace.3.2Air Cleaning Equipment. A device orcombination of devices for removing orreducing contaminants from the air handler by an HVAC system.3.3 AHU; Air-Handling Unit. Those components ofthe HVAC system that power and movecirculating air.22. Related Standards, Guidelines and PublicationsThe list in Appendix A2 is not all-inclusive butcontains items considered part of the body ofcurrent and recognized standards of goodpractice. All codes, regulations, standards,guidelines, and publications are subject torevision. Users of the Guideline areencouraged to consult the most recent editionsof the codes, regulations, standards,guidelines, and other publications listed.3. DefinitionsDefinitions explain major and repeating termsas they are used in the Guideline. Not allterms in the Guideline are defined withexactness, for example, experienced andappropriately dry, because the definitionmay vary with the time, the equipment, usage,and so forth. Indeed, many recommendationsare purposely left undefined to assureflexibility for the user. The user may find ithelpful to obtain the services of a cognizantauthority to assist in the definition of terms,conditions, and recommendations not readilyunderstood.3.1User-defined acceptable concentrations mightinclude, for example, carbon dioxide at orbelow 700+ background ppm,,nondetectable odor level, x% of the OSHAPEL, and so forth. This definition is not inconflict with the ASHRAE 622001 definition ofacceptable air: Air in which there are noknown contaminants at harmful or irritatingconcentrations as determined by cognizantauthorities (e.g., toxicologists, industrialhygienists, or other appropriate professionals).3.2 Typically only particle filters are used in HVACsystems, but some may provide chemical andactivated charcoal filters for gases and vapors.Air-cleaning equipment may be specified toprotect air-handling equipment only, or maybe specified to protect occupants as well.3.3 Typically includes mixing plenum, filters,heating and cooling coils, and fans. (Seedescriptive Figure A3.3 in the appendix.)33.4 AMCA establishes certification criteria for fansand other air-moving equipment such aslouvers, dampers, air curtains, airflowmonitoring stations, acoustic attenuators.3.5 Normally associated with testing andadjustment of duct airflow controls (e.g.,dampers) to assure proper distribution ofdilution air to occupied spaces.3.6A term used also in ASHRAE 62, a cognizantauthority is a knowledgeable person or entitythe user can employ to assist in meetingrecommendations of the Guideline, forexample, industrial hygienists as the CAs fordetermining if an IAQ problem exists, atoxicologist as the CA for determining if achemical exposure is hazardous, a physicianfor determining if a person has a building-related illness, a government agency fordetermining compliance with a code orregulation, and so forth.3.7 It is a process that ideally continuesthroughout the life of the HVAC system, butmore commonly begins early in the designprocess and continues actively for the first fewyears of operation.3.9 Also, occupational stressor.3.10Use of computer-driven electronic controls.The control system may incorporate electronicand pneumatic controllers and may includeanalog as well as digital signaling from avariety of types of sensors and controllers.3.11 Contaminants thus leave the indoorenvironment as general building exhaust andrelief air. All supply air systems providedilution ventilation when they contain acomponent of fresh outdoor air of acceptablequality.3.12 For example, cold air introduced at the floorlevel that rises through thermal action toreturn grilles in the ceiling. In displacementventilation, mixing of contaminants in theclean air at the occupant location isdiscouraged.3.4 AMCA. The Air Movement and ControlAssociation.3.5 Balancing; air balancing. The proportioning ofairflows within the duct or distribution systemaccording to specified design criteria.3.6 Cognizant Authority (CA). A person or entitywho by education, training, or experience isable to define terms, determine correctapproaches, solve problems, answerquestions, and so forth.3.7 Commissioning. The process of ensuring thatsystems are capable of being operated andmaintained according to design intent.3.8Commissioning Plan. Documentation thatdefines the commissioning process.3.9Contaminant; Air Contaminant. A substance(dust, fume, mist, vapor, or gas) the presenceof which in air is harmful, hazardous, toxic(e.g., irritating), or creates a nuisance.3.10 DDC. Direct digital control. 3.11 Dilution, Dilution Ventilation, Dilution andRemoval Ventilation, Ventilation. Use ofuncontaminated (fresh, outdoor) air to mixwith potentially contaminated indoor air toreduce airborne concentrations ofcontaminants to acceptable concentrations.3.12Displacement Ventilation; Plug-Flow. Aircontaminant control in which air is induced tomove as a body in one direction.3.13Document; Documentation. The formal processof planning and recording decisions made bythe user or relevant others. 3.14 Ducts; Ductwork. Normally, elongated rigid orflexible enclosures, pipes, or tubes used toconvey air and static pressure from onelocation to another.3.15 Economizer; Economizer Operations.Generally, the use of up to 100% outdoor airfor cooling when the outdoor temperature isbelow the air handler discharge temperatureset-point.3.16 Guideline. Refers to this Guideline, AIHAGuideline 2-2004.3.17 Health maintenance. Maintaining homeostasisof occupants, thus promoting health and well-being; maintaining normally healthyconditions.3.18 HVAC system. Heating, ventilating, and airconditioning system. Generic term forventilation systems providing both thermalcomfort and dilution ventilation for IAQcontrol in industrial and nonindustrialemployee occupancies requiring control ofpotential health hazards.3.19 IH; Industrial Hygiene. The profession devotedto the anticipation, recognition, evaluation,and control of employee exposures to airbornecontaminants.3.20 Industrial Occupancy. An employee-occupiedlocation where industrial operations andproduction processes are carried out.3.21 LEV; Local Exhaust Ventilation. Ventilationapproach used to capture, control, contain,receive, and/or remove air contaminants atthe source.43.13 Also may include the written proceduresdeveloped for operating, testing, andmaintaining an HVAC system. It may alsoinclude written health and safety plans for useduring testing and operation and maintenance(O&M) procedures. 3.14 In the Guideline it can also mean mixingboxes and any enclosed path taken by the airin the HVAC system, not to include theoccupied space.3.15 Economizer cooling is used to offsetmechanical cooling when outside airtemperatures are typically 50 to 70F. Checkset-points on individual HVAC systems. Mosteconomizers include enthalpy as adetermining metric.3.17 Comfort is considered a component of goodmental and physical health and is alsodesirable because it influences productivityand performance.3.19More broadly, industrial hygiene is the scienceand art devoted to forestalling, anticipating,recognizing, evaluating, and controllinghazards and stressors in the workplace thatmay cause illness, injury, or discomfort. 3.20 Examples include a foundry floor, wood shop,welding operations, factory production floor. It is an employee-occupied location whereprimary air contaminants are generated byindustrial processes or is defined by theOccupational Safety and HealthAdministration (OSHA) as an industrialoperation and regulated by OSHA industrialstandards. (See also, NonindustrialOccupancy.)53.22 This includes infiltration (outside air leaks intothe building) and exfiltration (inside air leaksout to the environment). Leakage can alsooccur between rooms, hallways, and otherspaces within a building. Leakage can findpathways through wall sockets, elevator shafts,wiring chassis, ceiling tile frames, and so forth.Also known as migration.3.25 Examples include offices, conference rooms,cafeterias, break rooms, multipurpose rooms,and any location where primary aircontaminants are generated by nonindustrialsources, for example, humans, buildingmaterials such as carpets, outdoor sourcessuch as smoke or herbicides, tobacco smoking,natural sources such as mold spores andpollen, and so forth. Could include, however,infiltration into the occupied space of aircontaminants generated in industrial processesin remote or adjacent spaces (See also,Industrial Occupancy.)3.26 Typical OELs include permissible exposure limit(PEL, OSHA) workplace environmentalexposure level (WEEL, AIHA), recommendedexposure limit (REL, National Institute forOccupational Safety and Health [NIOSH]), andthreshold limit value (TLV, AmericanConference of Governmental IndustrialHygienists [ACGIH]).3.28 Similar and familiar terms include cleanintake air, fresh air, makeup air, new air,outside air, and OSA. Outdoor air is used(1) to replace air that is exhausted to outsidethe building or occupied space, and/or (2) todilute indoor contaminated air. The termoutdoor air or OA may also includeacceptably clean indoor air sources, such asair taken from a warehouse or hallway thathas access to an outdoor air source. It mightalso include return air that has been cleanedto outdoor air quality.3.22 Leakage. Air crossing the building envelopethrough unintentional openings such as doors,fenestration, cracks, and so forth.3.23 MERV. Minimum efficiency reporting value asestablished by ASHRAE 52.21999.3.24NAAQS. National Ambient Air QualityStandards established by the U.S.Environmental Protection Agency (EPA).3.25Nonindustrial Occupancy. An employee-occupied location or space where industrialoperations and production processes are notcarried out.3.26Occupational Exposure Limit (OEL). A time-weighted average concentration ofcontaminant in air not to be exceeded in thebreathing zone of employees.3.27Occupied Space. Indoor space whereemployees are located.3.28Outdoor Air (OA). Acceptably clean airoriginating normally from outside the building.63.29 Examples of such components include OAdampers, minimum OA controls, return/relieffans, CO2-demand control systems, and soforth.3.31 Pressurization is used to prevent infiltration,smoke control, and for isolation strategies.3.32 Pulvation is the particle equivalent of theevaporation of liquids. Particles are normallypulvated by physical action (wind, vibration).3.33 Relief air is used predominantly duringeconomizer cooling.3.36For OH&S professionals the most acceptablesmoking policy is one in which smoking iscontrolled such that nonsmoking employeeshave the right to remain unexposed to tobaccosmoke.3.39 The user of the Guideline could be definedasbut is not limited tothe employer(usually the ultimate user), the building owner,the building supervisor, the buildingmaintenance supervisor, the HVAC systemoperator, an industrial hygienist, a renovator,and so forth. The definition of user variesbetween Guideline paragraphs and mayinvolve individuals with different assignedresponsibilities, local environmental factors,building and HVAC types, and so forth.Examples of typical users are provided in someparagraphs.The intent of using the general term user inthe Guideline is to encourage and suggest theassignment of responsibility to the appropriateperson, but in a way that allows flexibility forusers of the Guideline.3.29 Outdoor Air Ventilation System. Thosecomponents of the HVAC system responsible forbringing fresh outside air into the building andremoving/relieving used air from the building.3.30 Plug flow. See Displacement Ventilation.3.31 Pressurization. Technique using pressuredifferentials to induce airflow in an intendeddirection.3.32Pulvation. The action of particles becomingairborne.3.33 Relief Air. Air leaving the building throughdesigned, powered, or barometricallycontrolled openings to the outside.3.34RRR. Remodeling, repairing, and redecorating.3.35 Return Air. Air removed from an occupied andconditioned space that is either recirculated orexhausted.3.36 Smoking Policy. A policy established by theuser that defines or specifies the limitations orlocations associated with smoking of tobaccoproducts in the workplace.3.37 Supply Air. The total amount of air delivered toa space used for ventilation, heating, cooling,humidification, and dehumidification.3.38 System. See Ventilation System.3.39User. Refers to the person or entity using theGuideline, that is, those responsible for themanagement, operation, testing, and/ormaintenance of the HVAC system.7Explanatory Materials 4. General Guidance4.1 Traditional approaches include local sourceexhaust ventilation, source emission control,isolation, personal protection, spacepressurization, barriers, and so forth. ThisGuideline primarily covers the use of dilutionventilation through HVAC systems as a controlstrategy. When there are specific emissionsources, other controls used in conjunction withdilution ventilation are usually cost-effective.Dilution ventilation alone should not be usedfor the control of highly toxic materials.4.2 See Section 5 for details for following thisrecommendation.As it applies to this recommendation, the userwould normally be the employer or buildingowner.4.3 HVAC system operators (such as licensedstationary engineers and others qualified bytraining and experience) can be educated in thebasics of the HVAC system function and how todetermine proper performance. Testingpersonnel can be trained in testing and balanc-ing procedures; maintenance personnel, insafety procedures and maintenance functionssuch as found in ASHRAE 622001: Section 8;and so forth. The user or a cognizant authoritycan determine the extent to which systemoperators should be qualified or trained,depending on system complexity, building type,and so forth.4.4Clean HVAC systems help avoid nuisanceand combustible dust accumulations andmicrobiological activity in the HVAC system.See Section 6 for details.The terms appropriately dry and clean can bedefined by the user or by a cognizant authoritybased on conditions found in the system, thespace, the weather, and so forth.3.40 Ventilation System. The dilution ventilationsystem; the HVAC system; the buildingventilation system and its components.Suggestions and Objectives4. General Guidance4.1 Traditional industrial hygiene air contaminantcontrol strategies (other than dilutionventilation) should also be considered whenapplying the Guideline.4.2 Written management policies and programsshould be established by the user to assureeffective observance of the Guideline.4.3 Persons operating, maintaining, or testing anHVAC system should be qualified by trainingor experience to perform the job.4.4 The HVAC system should be kept clean andappropriately dry, and the equipment shouldbe maintained in good working orderthroughout its working lifetime.7Explanatory Materials 4. General Guidance4.1 Traditional approaches include local sourceexhaust ventilation, source emission control,isolation, personal protection, spacepressurization, barriers, and so forth. ThisGuideline primarily covers the use of dilutionventilation through HVAC systems as a controlstrategy. When there are specific emissionsources, other controls used in conjunction withdilution ventilation are usually cost-effective.Dilution ventilation alone should not be usedfor the control of highly toxic materials.4.2 See Section 5 for details for following thisrecommendation.As it applies to this recommendation, the userwould normally be the employer or buildingowner.4.3 HVAC system operators (such as licensedstationary engineers and others qualified bytraining and experience) can be educated in thebasics of the HVAC system function and how todetermine proper performance. Testingpersonnel can be trained in testing and balanc-ing procedures; maintenance personnel, insafety procedures and maintenance functionssuch as found in ASHRAE 622001: Section 8;and so forth. The user or a cognizant authoritycan determine the extent to which systemoperators should be qualified or trained,depending on system complexity, building type,and so forth.4.4Clean HVAC systems help avoid nuisanceand combustible dust accumulations andmicrobiological activity in the HVAC system.See Section 6 for details.The terms appropriately dry and clean can bedefined by the user or by a cognizant authoritybased on conditions found in the system, thespace, the weather, and so forth.3.40 Ventilation System. The dilution ventilationsystem; the HVAC system; the buildingventilation system and its components.Suggestions and Objectives4. General Guidance4.1 Traditional industrial hygiene air contaminantcontrol strategies (other than dilutionventilation) should also be considered whenapplying the Guideline.4.2 Written management policies and programsshould be established by the user to assureeffective observance of the Guideline.4.3 Persons operating, maintaining, or testing anHVAC system should be qualified by trainingor experience to perform the job.4.4 The HVAC system should be kept clean andappropriately dry, and the equipment shouldbe maintained in good working orderthroughout its working lifetime.4.5 A tobacco smoke ventilation policy and/orprogram should be established.4.6 The user should establish policies andprocedures to maintain indoor air qualityduring remodeling, repairs, and redecorating.84.5 In practical terms a smoking policy or programmeans a no-smoking policy or a separation ofsmokers from nonsmokers program and howto achieve cost-effective compliance with thepolicy or program.The tobacco smoke ventilation policy orprogram might include locations wheresmoking is not permitted; locations wheresmoking is permitted; provision for dedicatedHVAC systems for spaces where smoking ispermitted; provision for air in smoking locationsto be directly exhausted to the outside; smokecontrols; compliance with ASHRAE 62.1addenda on smoking; and so forth. Tobacco smoke controls could include dilutionventilation (through the HVAC system orthrough a dedicated system); local or generalexhaust ventilation; displacement ventilation;space pressurization schemes to keep smokingspaces under negative pressure comparedwith surrounding areas (e.g., hardwallbarriers); and so forth. The policy might also include smoking-cessation programs and other administrativeactivities.AIHA recognizes that the hospitality industry(e.g., bars, taverns, hotel lobbies, restaurants,casinos, bowling alleys) is a special (andsometimes difficult) employee occupancy thatwill require the employer or building owner tofollow local codes and to adopt smokingpolicies and use ventilation approachesuniquely suited to the situation.4.6 Not having an RRR policy could result in RRRactivities overloading the existing HVACsystems ability to provide adequate dilutionduring such work. Typical RRR policies mightcontain the following provisions. Purchase of low-emitting RRR materials(see Appendix 4.6) Off-gassing or airing out of materialsbefore they are taken into the building. Painting furnishings and applyingsealants/adhesives outside the building Painting and applying adhesives beforetextiles, carpets, or fleecy furnishings arebrought into the RRR area Isolating the RRR area from the rest of thebuilding (e.g., usingtemporary barriers andpressurization)9 Conducting RRR activities during off-workinghours Operating the HVAC at high-OA levelsduring RRR and for 13 months after RRRactivities cease Providing auxiliary dilution air, if necessary Making sure building envelopes andmoisture barriers are maintained to initialdesign specifications4.7 Occupants can be instructed in the basicfunctioning of the HVAC system to perhapsinclude operation of thermostats; humidistatsand adjustable supply registers and terminals;proper use of mixing or cooling fans; portableheaters; portable humidifiers; whom to contactwhen problems arise; conditions should beadjusted; and so forth. It should be noted thatin many buildings occupants have little or nodirect control of HVAC operations. In thesecases the HVAC operator must be contacted tomake changes, e.g.,, in air delivery rate, airtemperature, and so forth.4.8 The Guideline should not be used formarketing purposes. A claim that new HVACequipment is AIHA Guideline 22004compliant, for example, can be misleadingbecause it does not take into accountinstallation and on-going operatingconditions.5. Management of HVAC Systems Used for Dilution5.1 Performance standards are normallyestablished during the HVAC design stage.During commissioning, the system should havebeen evaluated against design performanceintentions. At later dates, following buildingand occupancy changes, the User mightreview dilution ventilation- and air quality-related performance standards and revisethem to reflect the current situation. Suchstandards could include, for example (but notbe limited to): Hours of operation Air volume flowrate specifications Outdoor air control system set points. Air cleaning standards of performance. Air mixing potential. Temperature and humidity set points (whencomfort is a consideration)4.7 Occupants should be provided withinformation on proper HVAC operating andcontrol procedures for the space.4.8 HVAC equipment suppliers and users of theGuideline should not claim compliance withthe Guideline unless every element iscomplied with.5. Management of HVAC Systems Used for Dilution5.1 The user should review or establish dilutionand air quality performance standards for theHVAC system.9 Conducting RRR activities during off-workinghours Operating the HVAC at high-OA levelsduring RRR and for 13 months after RRRactivities cease Providing auxiliary dilution air, if necessary Making sure building envelopes andmoisture barriers are maintained to initialdesign specifications4.7 Occupants can be instructed in the basicfunctioning of the HVAC system to perhapsinclude operation of thermostats; humidistatsand adjustable supply registers and terminals;proper use of mixing or cooling fans; portableheaters; portable humidifiers; whom to contactwhen problems arise; conditions should beadjusted; and so forth. It should be noted thatin many buildings occupants have little or nodirect control of HVAC operations. In thesecases the HVAC operator must be contacted tomake changes, e.g.,, in air delivery rate, airtemperature, and so forth.4.8 The Guideline should not be used formarketing purposes. A claim that new HVACequipment is AIHA Guideline 22004compliant, for example, can be misleadingbecause it does not take into accountinstallation and on-going operatingconditions.5. Management of HVAC Systems Used for Dilution5.1 Performance standards are normallyestablished during the HVAC design stage.During commissioning, the system should havebeen evaluated against design performanceintentions. At later dates, following buildingand occupancy changes, the User mightreview dilution ventilation- and air quality-related performance standards and revisethem to reflect the current situation. Suchstandards could include, for example (but notbe limited to): Hours of operation Air volume flowrate specifications Outdoor air control system set points. Air cleaning standards of performance. Air mixing potential. Temperature and humidity set points (whencomfort is a consideration)4.7 Occupants should be provided withinformation on proper HVAC operating andcontrol procedures for the space.4.8 HVAC equipment suppliers and users of theGuideline should not claim compliance withthe Guideline unless every element iscomplied with.5. Management of HVAC Systems Used for Dilution5.1 The user should review or establish dilutionand air quality performance standards for theHVAC system.5.2 The user should develop a writtenmanagement policy that supports ongoingsuccessful performance of the HVAC system.10 Water treatment standards (biological,chemical, etc.)User, as used in this Section, would normallyrefer to the employer or building owner.5.2 No HVAC system can be successfully operated,or be properly maintained withoutmanagement involvement. The policystatement should contain such items as: Performance standards to be followed. Identification or assignment of a cognizantor responsible person. Assignment of roles and responsibilities forthose involved with the HVAC system. Suchresponsibilities might include, for example:For building owners: Plans for IAQ controlduring design, materials selection,construction and operating phases of new andremodeled buildings.For building managers: Keeps the HVACsystem clean and well maintained; plans forHVAC modifications during remodeling,repairs, and redecorating.For employers and supervisors of occupants:Establishes written HVAC system policies andprograms. Selects a person responsible for theHVAC system (HVAC Manager). Establishesan IAQ database for the building, HVACsystems, and occupants. Establishes arecordkeeping program. Establishes a smokingventilation policy and program. Provides apreventive maintenance program. Providestraining and education for HVAC staff.For HVAC system managers: Maintains HVACequipment in good working order. OperatesHVAC systems to optimize IAQ. Keeps HVACsystems clean and dry. Controls pests andmicroorganisms in HVAC systems. Providestraining for HVAC technicians. Recordkeeping provisions. Maintenance of up-to-date plans andspecifications. Development of emergency plans. Provisions for employee training. A tobacco smoke ventilation controlprogram. Provisions for testing and monitoring ofHVAC systems.11 Response to chemical, biological orradiological attacks.5.3 See Section 8.5.4 The program should include the followingelements: An inventory of AHU components requiringmaintenance. A list of tasks and frequency of taskperformance. Inspection procedures. Operating schedules to assure systemoperation during periods of significantactivity.See Section 8 for details.5.5 See Section 9 for details.5.6 Understanding and satisfaction with systemoperation helps occupants deal with thenormal transient problems that occur in allbuildings. The program should provide for theidentification of how complaints are filed,investigated and tracked. This should includeboth health- and comfort-related issues.5.7 As a minimum, the following records are oftenkept: Training of HVAC personnel. Test and balancing results. As-built HVAC plans and specifications. Deficiencies identified during testing andinspection and corrective actions taken. Commissioning plan changes/updates HVAC/IAQ-related occupant complaints andactions taken to resolve concern(s). Water treatment records Maintenance schedules and documentationMaintenance records5.3The user should assure that HVAC systems areoperated and maintained by those with propertraining and credentials following recognizedstandards of good practices and equipmentmanufacturers recommendations.5.4 The user should develop and implement awritten HVAC system preventive maintenanceprogram.5.5 The user should establish and maintain awritten HVAC system testing and monitoringprogram.5.6 The user should establish a program torespond to occupants who have IAQ/HVAC-related complaints.5.7 The user should establish and maintain anHVAC system recordkeeping program.6. HVAC System Equipment6.1 HVAC equipment and components should bekept appropriately dry and clean.126. HVAC System Equipment6.1 Most surfaces within the HVAC system mustremain dry to prevent microbial growth, whichif allowed to proliferate could result incontamination, exposures to occupants, andodors. Some surfaces, such as chiller coils andcondensate trays, routinely become moistduring normal cooling-operation periods.These areas should be routinely inspected,and trays should completely drain to preventpooling of condensate water.The use of disinfectants and other biocides incondensate trays is not advised, because traysthat properly drain and are periodicallycleaned do not need disinfectants to preventmicrobial growth.Interior surfaces of HVAC systems should befree of significant quantities of accumulateddust and debris.Treatment and coating of interior AHUsurfaces should be done only with productsspecifically registered with EPA for use inHVAC systems. In addition, the product labelmust contain clear detailed instructions forhow and when to apply the product, and theseinstructions should be followed, as instructedby EPA. See Appendix A6.1.A clear and universal definition of clean andsignificant quantities cannot be provided.The user must determine appropriatedefinitions for the circumstances, equipment,and conditions involved. For example, whatone person may see as dirty may be a quitewell-maintained and nonproblem 30-year-oldduct system. Or, a small amount of odor-producing dust in a duct may be a significantquantity, whereas a thicker layer ofnonpulvating, nonodorous dust may not.See Sections 6.18 and 6.19 for additionalinsight and guidance. See Appendix 6.1 forinformation on cleaning approaches.Interior surfaces can be inspected periodicallyto determine if cleaning is necessary, forexample, once or twice per year. AHU surfaces(e.g., heating and cooling coils, condensatetrays, other major surfaces within the airhandler/fan coil unit) should be cleaned on ascheduled basis (e.g., once per year). Such13cleaning should avoid the use of chemicalagents that could result in contaminating thesupply air or corroding internal surfaces. (Ductsurfaces should not need routine or scheduledcleaning if the AHU is kept reasonably cleanand proper filters are used.) 6.2 As it relates to good working order, HVACcontrols, such as electrically or pneumaticallyoperated systems (e.g., variable air volumeboxes, dampers) and sensors (e.g.,temperature and pressure sensors, smoke/firesensors, damper position sensors, watertemperature) may fail or need adjustment overtime to accurately reflect the measurementparameter.Additionally, without routine inspections andcalibrations the system will fail to maintainproper pressures, airflow rates, and thermalconditions. System component manufacturerscan offer guidance concerning appropriateschedules for such inspections andcalibrations. Such inspections and calibrationsshould be documented to assist in futureefforts or troubleshooting. See Sections 8 and9 for more detail.6.3 The user must take care that adequateseparation is maintained between exhausts(e.g., attic exhausts, bathroom exhausts,combustion gas flues, laboratory chemicalhood exhausts, parking garages, coolingtowers, and other sources of air contaminantsor excessive heat or cold air) and air intakesduring any renovations, remodeling, oradditions to the buildings ventilation systems.Refer to Chapter 16, Airflow AroundBuildings, ASHRAE Handbook 2001,Fundamentals Volume, for guidance.The user, in this context, could refer to thebuilding maintenance supervisor or therenovation engineer or architect.The term well above and away can bedefined by the user or by a cognizant authoritybased on conditions found in the system, theroof, the weather, and so forth.6.4 Surfaces and areas near OA intakes areinspected to ensure the area is free ofexcessive debris, animal and insect pests (e.g.,birds), apparent microbial growth, vegetationgrowth, and standing water. The presence of6.2 HVAC system controls and sensors should bemaintained in good working order, and thesecomponents should be inspected andcalibrated to ensure proper operation.6.3 Building and process exhaust stack outletsshould be maintained well above and awayfrom outdoor air (OA) intakes.6.4 Areas adjacent to OA intakes and air mixingplenums should be kept clean and dry.6.5 Air intakes should be provided with security toguard against accidental or intentionalcontamination.6.6 Air intake louvers should be maintained tomeet AMCA 501 standards.6.7 Water-based cooling towers, evaporativecondensers, and other water mist generatingequipment should be provided with a writtencontrol program to minimize microbiologicalactivity.6.8 Access to water-based cooling towers,evaporative condensers, and other water mistgenerating equipment should be restricted bythe user.14these materials may block air inflow and/orcreate odors and health hazards if there aresignificant accumulations.The terms clean and dry can be defined bythe user or by a cognizant authority based onconditions found in the system, positions of theintakes and plenums, the weather, the season(what happens when it snows?), and so forth.6.5 Common problems include the smoking oftobacco products near the OA intake and theuse of herbicides/pesticides on vegetationlocated near the intake.OA intakes could be potential targets forpurposeful introduction of air contaminants oroffensive odors into buildings. Appropriatesecurity measures should be taken to preventsuch an occurrence. The degree of security isdictated by the sensitivity of the structure to beprotected, the likelihood that any particularstructure may be a target for a malicious act,and the impact that shutting down orevacuating any particular building due topurposeful contamination may have. Commonsecurity measures include the following. Limiting access to air-handling equipmentand OA intakes, such as in lockedmechanical rooms Placing OA intakes in secure areas withlimited access, such as on rooftops Erecting security fences around OA intakes The use of security monitoring equipmentsuch as access alarms, cameras, smoke andchemical detection equipment6.6 AMCA-certified air intake louvers restrict waterinfiltration and reduce static pressure losses.(See Appendix A.2.)6.7 Water mist generating equipment may betreated and/or operated to prevent hazardousmicrobial growth. OA intakes should bepositioned well away from mist generatingequipment to prevent entrainment. Refer toASHRAE Guideline 12, Minimizing the Risk ofLegionellosis in Building Water Systems.6.8 Access to areas near mist generatingequipment that could harbor microorganismsshould be restricted to minimize exposures.The user, in this context, might refer to thebuilding operator who will establish accesslimits.156.9 After-installation modification of inlet damperlocations, installation of sound insulators,improper storage of equipment and materials,and other changes in the mixing box candisrupt the mixing of OA and return air. WhereHVAC equipment rooms are used as mixingchambers (nonducted returns and/ornonducted OA intakes), they should be keptclean and not used for storage.Mixing boxes should also be kept free ofaccumulations of dust and debris.6.10 Proper selection and use of replacement airfilters is essential to the proper operation andmaintenance of HVAC equipment. Many existing building operators will employnew filters not specified during design andconstruction.Filters help prevent accumulation of dust anddebris on critical system components and helpto keep internal surfaces clean. Filter housingsshould be maintained to ensure appropriateairflow through the filter. If high-efficiencyparticulate air (HEPA) filters or other types ofair cleaners are used, refer to appropriatestandards for those air cleaners.6.11If AHU shutdown is required to change filters,this is often performed when the system isnormally shut down (e.g., after hours or onweekends). Changeout procedures shouldfollow manufacturers recommendations. See also Section 9.When they are available, the user mightfollow manufacturers recommendation forfilter testing, changing, and maintenance, forexample, as found in published O&Mmanuals.6.12 Airflow dampers (such as minimum OAdampers, economizer dampers, return airdampers, relief air dampers) are inspected toensure proper operation, for example, every 3months for OA louvers and actuators andevery 6 months for other components. Poorlyworking dampers can result in inadequate andinconsistent air distribution.6.9 Air mixing box configurations should bemaintained to assure thorough mixing of OAand return air.6.10 Replacement filters should be selected inaccordance with ASHRAE 52.11992 andASHRAE 52.21999.6.11 The user should retain (or establish) testingand maintenance programs to assure reliableand consistent operation of the air filteringand cleaning equipment. 6.12 Airflow dampers should be routinely inspectedandmaintained in good working order.6.13 Airflow through wet cooling coils should notstrip water from the coils nor allow mist toimpinge or settle on downstream surfaces.6.14 Condensate drainage from the air-handlingsystem should remove liquid water and remainclean and free of standing water.6.15 The user should maintain appropriatemechanical guards, lockout/tagout provisions,and fall protection provisions to assure safeinspection, operation, and maintenance ofmoving equipment such as fans, shafts, andbelts.6.16 Humidification equipment should be operatedto avoid microbiological growth in the supplywater and to prevent introduction ofpotentially hazardous chemicals in the supplywater. Disinfection of supply water, and theuse of additives, should follow themanufacturers recommendations.166.13 In some cases airflow through the system isincreased to meet airflow requirements. Thisnew high-velocity airflow through wet coolingcoils may strip water mist off of the coils,creating wet surfaces downstream andallowing for microbial growth and corrosion tooccur.Where this is found to be a problem, reduceair velocities through the coil to prevent thisfrom occurring, or install nonadsorbing anddraining baffles to capture the mist. Surfacesdownstream of cooling coils should beinspected to determine if microbial growth isoccurring. Treatment and coating of surfacesto inhibit the growth of mold and bacteriashould be done only with products specificallyregistered with EPA for use in HVAC systems.6.14 The user must assure that standing water isnot allowed to accumulate in the air-handlingunit. The drain line should include a watertrap. User, in this context, might refer to thebuilding operator.Users may want to review the ASHRAEFundamentals Handbook coverage ofconfiguration of condensate drains. SeeAppendix A2.6.15 The user will develop a comprehensiveoccupational health and safety program thatincludes provisions similar to these. Relevantsafety information is available from OSHA, theNational SafetyCouncil, and others.When maintenance and repair requirepersonnel access to the point of operation ofmoving parts, proper lockout and taggingprocedures can be followed to preventunexpected start up of the equipment.Fall protection is often necessary whenmaintenance personnel are working on AHUsmounted on sloped roofs.See also Section 8.6.6.16 Humidification equipment can introducemicrobial contaminants and chemicalcontaminants to the HVAC system.Humidification systems should be operatedaccording to manufacturers procedures andshould be rigorously maintained andinspected. Chemical additives must be17carefully used and should not result indetectable amounts of airborne water-treatment chemicals in the occupied space.Ideally, no chemical additives will be used inthe steam used to humidify supply air.Steam humidification systems using distilled orreverse-osmosis treated (RO) water may beused where feasible, and may be required insome areas where high levels of chemicaladditives are used to prevent scale and otherdeposits from occurring. Humidificationequipment must be routinely inspected duringoperation. 6.17 Internal duct linings can sometimes supportthe accumulation of dirt and moisture and thepotential for biological growths. Contaminatedduct liner should normally be removed andnot cleaned unless the lining was specificallyintended to be cleaned.Uncoated and uncovered fiberglassreplacement linings should be avoidedbecause of the potential for fiber erosion,sloughing, and the resulting degradation ofthe occupied space.The terms dry and clean can be defined by theuser or by a cognizant authority based onconditions found in the system, the equipment,the weather, and so forth.6.18Duct cleaning should be performed aftercareful analysis, because cleaning is difficult toperform and its effectiveness is sometimesquestionable. Small areas of limited dustdeposition are normal in many older ductsystems, often do not adversely contribute tothe presence of air contaminants in thebuilding, and rarely interfere with airflow.This recommendation primarily applies to theair supply system, but return ductwork shouldbe included in this recommendation asappropriate and necessary. For example, ifmold growth or combustible dust are found inreturn ductwork, it will need to be remediated.The presence of microbial growth,accumulations of significant deposits ofcombustible dust (e.g., paper dust), andevidence of other hazardous deposits shouldbe removed by thorough cleaning, or theducts should be replaced.6.17 Interior duct sound and thermal linings shouldbe maintained dry and clean.6.18 Ductwork and interior surfaces of the AHUshould be cleaned or corrected when any ofthe following conditions exist. Permanent or chronic water damage orinfiltration Presence of visible mold growth or slime Dust or debris is present that restricts airflow Evidence exists that significant amounts ofcombustible dust is present in the ducts Evidence that significant amounts of dust ordebris are being emitted from the system Offensive odors are emitted from the HVACsystem and evidence exists that the odorsource is present in the ducting, andcleaning is shown to be an effective solution6.19 Duct and system cleaning should beperformed in accordance with recognized ductcleaning guidelines.18Cleaning porous surfaces, such as thermal orsound insulation, is difficult and may not beeffective or remove sufficient amounts of thedeposits. Cleaning these surfaces may releaseinsulation materials such as fibrous glass.If duct cleaning is to be performed, a writtenspecification should be prepared. The workshould be conducted by a firm that is qualifiedand experienced in cleaning similar systems.References should be checked. The workshould be inspected prior to activating theHVAC system.When sound or thermal linings are locatedwithin the first 20 feet of the air handling unit,they are more likely to become contaminatedthan in other locations and should beinspected and cleaned periodically, asnecessary. Such linings need not be cleaned ifinspection shows linings are clean and dry. Insome cases cleaning of linings will beineffective or impossible and they will requirereplacement. See Appendix 6.1 for moreinformation on cleaning methods.Open plenum space, when used as a returnplenum, should be maintained at the samelevel of cleanliness as duct interiors. Leaks orwater damaged insulation and ceiling tilesshould be quickly remediated.During inspection of ductwork it is also usefulto look for physical damage (crushedductwork, damaged equipment), corrodedduct sections, and loose, damaged, friable, ormissing insulation.The terms significant amounts of dust andoffensive odors can be defined by the useror by a cognizant authority based onconditions found in the HVAC system, theoccupied space, complaints, and so forth.6.19 The user might obtain and follow, for example,National Air Duct Cleaners Associations(NADCAs) guide, ACR 2002 Assessment,Cleaning, and Restoration of HVAC Systems, asappropriate. SMACNA also provides ductcleaning standards and assistance, SeeAppendix 6.1 for information on commoncleaning methods.The duct-cleaning firm should normally becertified (e.g., by the Sheet Metal and Air19Conditioning Contractors National Association(SMACNA), NADCA, or other testing andcertifying organizations.6.20 This may, in some cases, require thereplacement of equipment and materials, forexample, sound insulation inside ductwork, orreplacement of duct system or AHUcomponents in extreme cases.6.21 The proper operation of rebuilt or replacedHVAC equipment may be confirmed using acommissioning process. New or substantiallyreplaced or rebuilt HVAC systems could bebalanced and airflow verified according torelevant standards (e.g., ASHRAE Standard111). Condensate drain pans might be testedto verify proper drainage, for example.6.22 Generally, applications of biocide orantimicrobial products inside supply or returnductwork should be avoided. When suchproducts must be used, only U.S. EPA-registered products labeled for use in HVACsystems should be employed. EPA has alsopublished specific warnings about thepotential misuse and subsequent risks tobuilding occupants associated with EPA-registered products not intended for use inHVAC systems. (See more information in theappendix.)7. Outdoor Air (OA)7.1 Changes almost always occur in theoccupancy rate or building HVAC equipmentafter construction that require changes in thequantities of OA supplied to various spaces inthe building.OA is normally acceptably clean airoriginating from outside the building. SeeSection 3 for a complete definition of OA as itis used in this Guideline.Air supplied to an occupied space may consistof all OA (e.g., 100% OA, straight-throughventilation, economizer operations,dedicated OA system), or more commonly,air consisting of mixed return and OA (e.g.,80% return air mixed with 20% outside air).Generally speaking, it is only clean fresh airthat creates steady-state dilution of air6.20 Visible mold or fungal growth in any part ofthe HVAC system should be removed and thesource of the original moisture and organicmaterials determined and controlled.6.21 After replacement or major modifications ofHVAC system components, the system shouldbe reevaluated for IAQ impacts.6.22 Use of biocides or antimicrobial treatments inHVAC systems, either for remediation orpreventative treatment, should be monitoredand controlled in accordance with EPAguidelines for the specific registrationproperties of the product.7. Outdoor Air (OA)7.1 As conditions in the building change, outdoorairflow rates supplied to the occupied spacefor dilution should be maintained or adjustedto assure that sufficient air is provided todilute air contaminants to user-definedacceptable concentrations in the occupiedspace.19Conditioning Contractors National Association(SMACNA), NADCA, or other testing andcertifying organizations.6.20 This may, in some cases, require thereplacement of equipment and materials, forexample, sound insulation inside ductwork, orreplacement of duct system or AHUcomponents in extreme cases.6.21 The proper operation of rebuilt or replacedHVAC equipment may be confirmed using acommissioning process. New or substantiallyreplaced or rebuilt HVAC systems could bebalanced and airflow verified according torelevant standards (e.g., ASHRAE Standard111). Condensate drain pans might be testedto verify proper drainage, for example.6.22 Generally, applications of biocide orantimicrobial products inside supply or returnductwork should be avoided. When suchproducts must be used, only U.S. EPA-registered products labeled for use in HVACsystems should be employed. EPA has alsopublished specific warnings about thepotential misuse and subsequent risks tobuilding occupants associated with EPA-registered products not intended for use inHVAC systems. (See more information in theappendix.)7. Outdoor Air (OA)7.1 Changes almost always occur in theoccupancy rate or building HVAC equipmentafter construction that require changes in thequantities of OA supplied to various spaces inthe building.OA is normally acceptably clean airoriginating from outside the building. SeeSection 3 for a complete definition of OA as itis used in this Guideline.Air supplied to an occupied space may consistof all OA (e.g., 100% OA, straight-throughventilation, economizer operations,dedicated OA system), or more commonly,air consisting of mixed return and OA (e.g.,80% return air mixed with 20% outside air).Generally speaking, it is only clean fresh airthat creates steady-state dilution of air6.20 Visible mold or fungal growth in any part ofthe HVAC system should be removed and thesource of the original moisture and organicmaterials determined and controlled.6.21 After replacement or major modifications ofHVAC system components, the system shouldbe reevaluated for IAQ impacts.6.22 Use of biocides or antimicrobial treatments inHVAC systems, either for remediation orpreventative treatment, should be monitoredand controlled in accordance with EPAguidelines for the specific registrationproperties of the product.7. Outdoor Air (OA)7.1 As conditions in the building change, outdoorairflow rates supplied to the occupied spacefor dilution should be maintained or adjustedto assure that sufficient air is provided todilute air contaminants to user-definedacceptable concentrations in the occupiedspace.7.2. OA used for dilution should be clean.20contaminants. Recirculated (return) aircannot provide dilution in the steady-statecondition.User-determined acceptable concentrationsare normally established and documented foreach occupied space. For example, Theaverage acceptable concentration will be one-half of the TLVin the space under the worstconditions, and to below 5% of the TLV duringnormal operation; or Carbon dioxideconcentrations will not exceed 700+ambientppm during normal operating conditions, andso forth.Appropriate acceptable concentrations can bechosen by the user in consultation with anindustrial hygienist or other cognizantauthority. The user may estimate or measureairborne contaminant concentrations in theoccupied space during various operations orconditions using traditional industrial hygieneapproaches.Typical indoor airborne concentrations innonindustrial occupancies with triggerconcentrations are summarized in AppendixA7.1.Acceptable concentrations may be chosen forspecific air contaminants known or thought tobe possible in the space (e.g., volatile organiccompounds or carbon monoxide) or forsurrogate gases and vapors in air (e.g., carbondioxide, which can be a surrogate indicator ofthe amount of dilution air being introduced toa space; or water vapor, which might be asurrogate for the potential growth of mold).This provision does not preclude the use ofmore cost-effective controls, for example,emission source controls when they are morecost-effective. Indeed, use of other controlscan reduce the need for dilution ventilation.7.2 This provision suggests the use of dilution andOA that meets minimum standards ofcleanliness, as reflected in U.S. EPA NationalAmbient Air Quality (NAAQ) standards andother recommended air concentrations. Anyair used for dilution (e.g., OA, air fromhallways or warehouses) should be evaluatedfor cleanliness to assure that safe and effectivedilution is accomplished and that user-definedacceptable concentrations are maintained in21the occupied space. See Section 3 for a morecomplete definition of OA.The user should establish good practices tomaintain a consistent delivery of clean air overtime, for example, use and maintain AMCA-certified louvers and grilles at air intakes; usebird screens on air intakes; restrict tobaccosmoking near intakes; maintain filters andscrubbers; keep mechanical and fan rooms ina clean and sanitary condition; discourage theuse of mechanical rooms as storage areas forcleaning supplies, landscape chemicals;manage the loading and unloading of vehiclesnear intakes and so forth.7.3 For most nonindustrial employee-occupiedspaces, following provisions of ASHRAE 622001 for estimating the required amount ofclean outdoor is usually acceptable.Addendum n of ASHRAE 62.1, when adopted,will change the determination of OA fromcfm/person to cfm/person plus cfm/sq ft.Even with that change, most employeeoccupancies will continue to receive 15cfm/person, or more. See Appendix A1.1 andA7.3 for additional information.Studies in Canada and elsewhere suggest thatemployee occupant complaints rise sharplywhen outside air delivery rates are less than15 cfm/person. (See Rajhans in AppendixA1.2.)The minimum flow rate of 15 cfm/personcoincides with carbon dioxide concentrationsof 10001100 ppm when backgroundconcentrations are 370450 ppm and humansare the only source of CO2.The user in this context might refer to thebuilding industrial hygienist.The user also should evaluate the effect ofdedicated exhaust systems (e.g., toiletexhausts, kitchen exhausts) on the delivery ofOA. For example, if the bathroom exhaustsare configured to be turned off with the lightswitch, how would that effect the delivery andmixing of OA in adjacent spaces?7.3 Appropriate OA volume flow rates should bedetermined by the user for each occupiedspace, but outdoor air flow rates should notnormally be less than 15 cfm per person inthe occupied space.7.4 Air supplied for dilution should be distributedthroughout the occupied space and withoutsignificant interruption.22For special employee occupancies not meetingthe criteria of the Guideline, the user canfollow traditional industrial hygiene methodsfor determining appropriate minimum dilutionvolume flow rates. See Appendix A1.1 fortypical approaches.7.4 This recommendation implies supplyingdilution air to the actual location of occupants.Simply supplying air to the building or to thespace does not meet the recommendations ofthe Guideline unless occupants receive thebenefits of dilution. In some cases provisionsfor greater mixing or distribution may berequired, for example, use of freestandingfans, lifting partitions from the floor, proper airbalance, and so forth.The user should recognize that the outside airventilation function of the HVAC system isoften designed for or controlled by comfort,not for dilution criteria. For example:(1) In some variable air volume (VAV) airdistribution systems, VAV boxes closecompletely when the thermostat is satisfied.This results in a complete shut down of theoutside air ventilation in the zone served bythat thermostat.(2) Many smaller office buildings are servedby modular or unitary HVAC units, in whicheach unit is controlled by a single spacethermostat. With the subbase fan switch inthe auto position the fan is thermostaticallycontrolled to deliver conditioned air to thespace on a call for heating or cooling onlyrather than running continuously to provideoutside air ventilation.(3) Many automatic temperature control(ATC) sequences favor comfort overventilation. For example, during heatingseason early morning warm-up controlschemes shut the OA damper until thebuilding reaches its occupied temperatureset-point. Mixed-air controllers also favorcomfort and close the OA damper when theair handler discharge temperature increasesabove a typical discharge set-point of 55Fduring cooling season.(4) In some VAV systems, supply fan airflowrate is diminished by dampers or fan speedto match VAV box requirements. Because the23total air supply flow rate is diminished, so isthe amount of OA pulled in to the system.Where this is the case (comfort takingprecedence over dilution), the user shoulddetermine whether airflow rates are sufficientfor proper dilution.7.5 The user will review (e.g., from the initialdesign) or determine the static pressurerelationships required in occupied spaces (re:adjacent spaces and the outside environment)and assure the continued provision of supplyand exhaust air volume flow rates and ratiosaccordingly.The user will normally evaluate the effect ofdedicated exhaust systems (e.g., toiletexhausts, kitchen exhausts, copy roomexhausts) and assure that changes in suchdedicated exhaust systems do not changeappropriate pressure relationships. Forexample, if the bathroom exhausts areconfigured to be turned off with the lightswitch, how would that effect thepressurization relationships?The volume flow rate of supply air is oftendesigned to be greater than the design returnvolume flow rate. However, in somecircumstances a slight negative pressure maybe required in an area to control fugitiveemissions and/or prevent migration of odorsor contaminants to other areas of the building.Actual static pressure differences betweenadjacent spaces are usually very low, notexceeding 12 Pa in most cases. Whenworking with existing spaces, flow rate may bea better indicator of pressurization differencesthan measuring actual pressure difference.For example, it is common HVAC design forbuildings to be under positive pressurecompared to the outside environment.This isdone to prevent the infiltration of moisture,dirt, and untempered air. If a user replaces arotating airlock door in a building lobby withsliding doors to improve access, then the lobbywill get cold in heating season and street levelcontaminants will be distributed throughoutthe building via the elevator shafts andtemperature stratification.In humid climates loss of positive buildingpressurization will allow infiltration of moisture7.5 Pressurization relationships established duringdesign should not be abandoned withoutconsideration and documentation of theconsequences.7.6 Outdoor air should be filtered or cleaned asnecessary and as feasible to meet therecommendations of paragraphs 7.1 and 7.2and to protect HVAC equipment.7.7 When VAV systems are used sufficient OAshould be supplied to meet therecommendations of paragraphs 7.1 and 7.2.7.8 OA that is mechanically heated or cooledshould be conditioned in accordance withASHRAE comfort standards.24into the building. Moisture may condense ondew-point surfaces in the building and supportmicrobial growth such as fungus (mold)growing on the back of vinyl wall coverings.Conversely, during cold, dry, winter weather,too much positive pressure in the building maycause warm moist air to exfiltrate through theinside wall and condense on cold surfacesnear the outside wall.7.6 In most cases OA is cleaned and conditionedafter it has mixed with return air. In somecases OA is prefiltered before mixing withreturn air. Typical filters to protect fans andcoils include ASHRAE 52.11992 arrestanceratings of 6090% and ASHRAE 52.21999minimum efficiency rating value (MERV)ratings of 610.If filtration is used to remove particulate for aircleanliness in the occupied space, the user canconsult ASHRAE 52.21999 for guidance onfilter selection.Feasibility issues may occur, for example,when older systems are to be retrofitted withmore efficient filters.7.7 ASHRAE 622001 allows for a lead/lag timefor ventilation functions. The user willdocument the procedure for providing therequired volume flow rate of OA air in VAVsystems during periods of reduced system flowrate.7.8 The World Health Organization has definedcomfort as an integral part of good health.Conditioning OA for thermal comfort impliesheating, cooling, humidifying, or dehumidify-ing air to meet the needs and desires ofoccupants of the space. ASHRAE 551992,Thermal Comfort, can provide guidance. Thesestandards suggest that 8090% of occupantswill be satisfied with relative humidities of3060% and temperatures of 6876F. Thesestandards, although normally consideredcomfort standards, indirectly affect humanhealth and well-being.This recommendation does not apply wherenatural ventilation is employed.257.9 Direct-fired makeup air equipment, in whichnatural gas or liquefied petroleum gas (LPG) isburned directly in the airstream, is sometimesused for tempering supply air in nonindustrialoccupational settings.ANSI Z38.18 establishes minimum standards,for example, a limit of 5000 ppm carbondioxide in the occupied space, adjustablefiring rates depending on temperature rise,and minimum OA requirements. (See ANSIZ38.18.) The following items also should be consideredin the selection and operation of direct-firedheaters. The heater is not subject to freezingproblems. The delivered air temperature can be easilycontrolled by modulating the flame, whichusually has a turndown ratio from 25-to-1 to45-to-1. Industrial installations should normally meetthe requirements of Industrial Risk Insurers(GE Capital or its successors), Factory Mutual(FM), and/or local codes. Generally, manualas well as automatic shutoff valves, gaspressure regulators, airflow switches, safetypilots, and high limit temperature controlsare required. One-hundred percent OA should behandled over the burner with air velocitiesbased on the burner manufacturersrecommendations. This velocity is usually inthe range of 2500 to 3000 ft/min (13 to 15m/sec). Burners may be either of the raw gas orpremixed type. When OA is subject to being dusty or dirty, itshould be filtered before it reaches thepremix burner. Direct fired units generate carbon dioxide,carbon monoxide, water, and other productsof combustion. When burners and controlsare properly selected, installed, andmaintained, these products of combustionshould not be a problem. When establishing user-defined allowableconcentrations, applicable codes andstandards of the authority having jurisdictionshould be consulted. See also GuidelineSection 7.1. Corrosive or flammable material should notcome in contact with the heating unit.7.9 Where OA and/or supply air is heated by adirect-fired heater, the following provisionsshould be followed. Comply with the provisions of the latestversion of ANSI Z38.18, Recirculating DirectGas-Fired Industrial Air Heaters. Combustion products should not createairborne concentrations in supply air inexcess of user-defined acceptableconcentrations. A monitor should be installed in the supplyair to monitor carbon monoxideconcentrations. Relative humidities should not exceed thatwhich produces condensation on interiorsurfaces. Applicable codes should be complied with. Manufacturer recommendations should becomplied with.7.10 Tobacco smoke-contaminated air fromsmoking-permitted areas should not bereturned to or passed through occupiedspaces.7.11 The user should monitor the amount ofdilution air delivered to the occupied space.8. Operation and MaintenanceThere are some existing buildings where oneor more Section 8 recommendations will beimpossible to apply because of the lack ofsystem capabilities. The user can simply notethat fact and make plans for upgrade at somefuture date, for example.8.1 HVAC system equipment should be operatedduring normal occupancy periods to ensureuser-defined dilution ventilation conditions aremaintained.267.10 Passed through does not mean air in ducts.It refers to air moving openly through theoccupied space. Returned to meansrecirculating the tobacco smoke-contaminatedair back to the AHU to be mixed with OA. Anexception to this provision is possible when airfrom a smoke-permitted areas is completelycleaned before recirculation.A cognizant authority can be utilized to helpdefine theseterms and approaches.7.11 The user can establish a program to monitorthe continued effectiveness of the HVACsystem in providing dilution ventilation (usuallyOA) to occupied spaces. The monitoringprogram can be based on the needs andcharacter of the space and system equipment.For example, in office spaces, the programmight call for a measurement at initialoccupancy and then again during the testingand balancing of the HVAC system.Provision 8.4.1.8 of ASHRAE 622001provides for an actual measurement of OAdelivery at least once every 5 years.Tracer gas approaches are acceptable. Acognizant authority can be used to help withthis approach.See Section 9 for more guidance.8. Operation and Maintenance8.1 HVAC operation may be required outside ofnormal occupancy periods to ensure thebuilding can be made comfortable prior tooccupant arrival, during off-hours occupancy(e.g., evenings/weekends or other periods oftime). Consideration should be given toensuring the occupied spaces are properlyventilated during janitorial activities, especiallyif janitorial products (or other maintenanceproducts such as paints, pesticides, adhesives,etc.) that generate air contaminants are beingused.7.10 Tobacco smoke-contaminated air fromsmoking-permitted areas should not bereturned to or passed through occupiedspaces.7.11 The user should monitor the amount ofdilution air delivered to the occupied space.8. Operation and MaintenanceThere are some existing buildings where oneor more Section 8 recommendations will beimpossible to apply because of the lack ofsystem capabilities. The user can simply notethat fact and make plans for upgrade at somefuture date, for example.8.1 HVAC system equipment should be operatedduring normal occupancy periods to ensureuser-defined dilution ventilation conditions aremaintained.267.10 Passed through does not mean air in ducts.It refers to air moving openly through theoccupied space. Returned to meansrecirculating the tobacco smoke-contaminatedair back to the AHU to be mixed with OA. Anexception to this provision is possible when airfrom a smoke-permitted areas is completelycleaned before recirculation.A cognizant authority can be utilized to helpdefine theseterms and approaches.7.11 The user can establish a program to monitorthe continued effectiveness of the HVACsystem in providing dilution ventilation (usuallyOA) to occupied spaces. The monitoringprogram can be based on the needs andcharacter of the space and system equipment.For example, in office spaces, the programmight call for a measurement at initialoccupancy and then again during the testingand balancing of the HVAC system.Provision 8.4.1.8 of ASHRAE 622001provides for an actual measurement of OAdelivery at least once every 5 years.Tracer gas approaches are acceptable. Acognizant authority can be used to help withthis approach.See Section 9 for more guidance.8. Operation and Maintenance8.1 HVAC operation may be required outside ofnormal occupancy periods to ensure thebuilding can be made comfortable prior tooccupant arrival, during off-hours occupancy(e.g., evenings/weekends or other periods oftime). Consideration should be given toensuring the occupied spaces are properlyventilated during janitorial activities, especiallyif janitorial products (or other maintenanceproducts such as paints, pesticides, adhesives,etc.) that generate air contaminants are beingused.278.2 The plan will be used by operators,renovators, maintenance personnel, and forparts inventory.The written operating procedures mightinclude the following. An inventory list of components of thesystem, such as OA intake louvers; OAdampers; OA damper motor operator;minimum OA controls; demand ventilationcontrols; mixed air controls; early morningwarm-up controls; VAV box minimumposition controls; return/relief fan; and soforth. Operating criteria for components of theventilation system including both (original)design intent and (current) operatingcriteria, for example, minimum volumetricairflow of OA per supply fan; total occupantsin zone served by each supply fan;volumetric airflow OA per occupant; ATCsequences affecting operation of OAventilation; building static pressure set-points; CO2demand ventilation system set-points; mixed air control set-points; morningwarm-up control set-points; start-up andshutdown times; and so forth. All documentation associated with theventilation system such as design drawings(red-lines); construction specifications; shopdrawings and submittals; ATC schematics;ATC written sequences of operation; test andbalance reports; and so forth.8.3 This recommendation is flexible and must betempered by local conditions, for example,filter change-out can occur on Tuesday ifintake louvers were leaking on Monday. 8.5 These might include air volume flow rate(cfm), relative humidities, and so forth.8.6 This provision includes providing safeoperating procedures to be followed duringmaintenance. Safety provisions will likelyinclude fall protection provisions, lockout/tagout provisions, potential sources ofcontaminants to be avoided, nip pointprovisions, and so forth.8.2 The user should develop written operatingprocedures for the operation of the HVACsystem.8.3 The user should operate the ventilation systemper the written operating procedures.8.4 The user should train operators of theventilation system per the written operatingprocedures.8.5 If instrumentation is provided, the operatorshould periodically record operatingmeasurements.8.6 Maintenance personnel responsible for HVACsystems should be instructed on their properoperation and the objectives for theinstallation.8.7 Maintenance personnel responsible for anHVAC system should be trained totroubleshoot the system in the event ofmalfunction.8.8 The user should establish a program ofpreventive and scheduled maintenance.8.9 The user should understand and follow theprovisions of ASHRAE 622001 Section 8 formaintaining HVAC equipment.8.10 Manufacturers recommendations for themaintenance of HVAC system componentsshould be considered when establishing themaintenance schedule.8.11 Operation and management of humidificationsystems should be tailored to the type ofhumidification equipment used.8.12 The user should establish and support aprogram to keep maintenance records.8.13 Drawings, plans and specifications should bekept up-to-date as the HVAC system changes.8.14 Occupants of a space served by an HVACsystem should be provided with information onproper HVAC operation, maintenance andcontrol procedures for the space.288.7 Troubleshooting in this context is the abilityrecognize problems and does not necessarilyrequire the ability to repair a problem.8.8 For an HVAC system to perform its designedfunctions, preventive and scheduledmaintenance is necessary. The program canbe tailored to the needs of the system.8.9 ASHRAE 622001 Section 8 contains minimummaintenance recommendations for filters; air-cleaning equipment; humidifiers;dehumidifying coils; drain pans; air intakes;control sensors; and cooling towers. TheGuideline sees these provisions as minimumcriteria.8.10 Exceptions could include recommendationsthat conflict with each other or are notfeasible.8.11 Humidifier operation and maintenance varywith the type of equipment, but panhumidifiers should be drained and cleanedregularly (depending on circumstances) and atthe end of the heating season. Makeup watervalves should be cleaned of scale or otherdeposits.8.12 It is useful to keep a log book of maintenanceservices and dates at or near the ventilationsystem. The responsibility for scheduledmaintenance should rest with a singleindividual who should also see that adequaterecords are maintained. Computerizedmaintenance records are generally acceptablewhen they are readily available to users. Users in this case might be the building owner,the HVAC operator, or the maintenancesupervisor.8.13 Every person testing, maintaining andoperating an HVAC system should have accessto and be familiar with the most recentlyupdated plans and specifications for thesystem.8.14 See also Section 4.7.299. Inspection, Monitoring, Testing, Balancing, and Operational Checks9.1 Air quality and dilution performance standardsare normally established during design andthen evaluated against the performancestandards during commissioning. Afterinstallation, performance standards should bereviewed periodically and, if necessary, revisedto reflect the current situation. User, in this context, might refer to thebuilding owner or building supervisor.Performance standards are the designcharacteristics of the HVAC system. They mayinclude dilution ventilation-related parameterssuch as volumetric flow rates (main ducts andbranches); supply, intake, and duct velocities;and return intake air volume ratios. They mayalso consider air conditioning parameters suchas temperature settings, heat transfer rates ofheating and cooling components, anddehumidifying capacity. They may also considerair-cleaning parameters such as filtrationcapacity, efficiency, velocity of air through thefiltering media, and pressure drop of filters.Operating outcomes define the ambientconditions of the occupied space expectedunder proper operation of the HVAC system.These conditions may include ambienttemperature and humidity; maximumacceptable concentration of CO2; ambient airvelocity in sensitive areas; mixing; maximumconcentration of contaminants of concern(paper dust, formaldehyde, ozone, carbonmonoxide, bioaerosols); cleanliness of interiorsurfaces; and any other dilution-relatedparameter identified by the user.9.2 HVAC systems are tested to be certain that theyperform according to design or operatingperformance criteria. Performance criteria (e.g.,the minimum outdoor airflow rate is 1000scfm; the static pressure drop across the aircleaner should not exceed 0.75 w.g., etc.) areuseful because testing and measurements canthen confirm satisfactory performance of theHVAC system in providing dilution ventilation.Instruments used to measure outcomes mayinclude IAQ monitors with probes fortemperature, humidity, and CO2concentration, and so forth.9. Inspection, Monitoring, Testing, Balancing, and Operational Checks9.1 Dilution and air quality performance standardsand operating outcomes, if not defined duringdesign and installation, should be establishedby the user for the HVAC system.9.2 The user should select testing, monitoring, andbalancing methods and instruments that canmeasure the performance standards andoutcomes of paragraph 9.1.9.3After system modification or building renovationthe HVAC system should be tested beforeroutine service begins, to assure that theHVAC system meets the establishedperformance criteria of paragraph 9.1.9.4 The HVAC system should be periodicallyinspected, tested, and/or monitored inaccordance with a schedule determined by theuser.30Testing and balancing firms may be employedto carry out these recommendations.9.3 In some situations modifications cannot befully evaluated. For example, sometemperature and humidity criteria may not betestable until proper environmental conditionspresent themselves.New ductwork and other AHU equipment usedin any modification or renovation projectshould normally be sealed before delivery tothe job site and remain sealed duringinstallation. (Unsealed equipment can becontaminated by renovation debris and moldfrom water infiltration e.g., rain.) Note,however, in warm, humid climates, sealingductwork may create a humid condition in theductwork suitable for the growth of mold.SMACNA recommends that the contractor capductwork and equipment ends for transportand then keep end caps on ductwork untilfinal connection. Testing protocols should consider seasonalimpacts, for example, summer, transitional,and winter operation.This recommendation normally applies only tothe portions of the building or HVAC systemmodified. Relocation of a supply diffuser inone office would not trigger a test of theentire system, for example.9.4 Objectives of inspection and testing shouldnormally include the following. Determination of the effectiveness of theventilation system (e.g., the quantity ofoutdoor air, dilution and mixingeffectiveness, occupant satisfaction,condition of the air cleaning system) Determination of the distribution of supplyair through the systems. Depending on thesystem design, this could be volumetric flowthrough each zone or airflow measurementat the supply fixture. For variable air volumesystems (VAV) the measurements may needto be made under several conditions. Monitoring of conditions throughout the lifeof system Continued compliance with appropriatebuilding code requirements andmanagement-determined performancecriteria31 Surfaces within the AHU, such as thecondensate drain pan, should be inspectedat least once per year. Mechanicallyoperated louvers such as used at the OAintake should be inspected more frequently,for example, every 3 months.9.5 The initial evaluation establishes baselineconditions. Periodic evaluations determineconformance with performance standards andchanges of baseline conditions. The frequencyof testing should be determined by the user.9.6 Such services are normally performed by atesting, adjusting, and balancing (TAB or T&B)technician who has been certified by theNational Environmental Balancing Bureau, theAssociated Air Balance Council, or othercertification groups. (See Appendix A2 foraddresses.) T&B firms and technicians usually do not havethe ability to determine if the HVAC systemcontrols the health hazard. A team approachmay be necessary.9.8 Calibration will follow, as a minimum,equipment manufacturers recommendationsand methods. The schedule usually followsthat recommended by the instrumentmanufacturer but may be modified asdetermined by the user (e.g., more frequentlywhen used more often.)9.9 The life of the ventilation system often exceeds20 or 30 years. Access to the original designintent, commissioning documents, history ofmodifications, and recent testing andbalancing reports allow for intelligentevaluation of the system and possiblemodifications. Consequently, some of theinformation should be maintained for the lifeof the equipment.9.10 When following ASTM D6245 guidelines, usersof carbon dioxide measurements should, forexample, measure outside air concentrations,calibrate monitoring equipment, takemeasurements at the appropriate times andplaces, and consider age, gender, and activity9.5 The HVAC system should be air balanced on aschedule determined by the user.9.6 Persons performing inspection, testing, andbalancing should be qualified by training,experience, or certification to perform thework.9.7 Testing and balancing instrumentation shouldbe suitable for the measurements to be taken.9.8 Testing and balancing instruments should becalibrated in accordance with manufacturersrecommendations.9.9 Records of testing and balancing should bemaintained by the user.9.10 Use of carbon dioxide as a surrogate measurefor outdoor air and dilution ventilation shouldfollow the guidelines of ASTM D6245.when using carbon dioxide as a measure ofdilution ventilation. Because the investigator isa significant source of carbon dioxide, extremecare is required to ensure accuratemeasurements.Keep in mind that carbon dioxide is notnormally considered a measure of air quality.It is usually only a measure of ventilation andOA delivery.9.11 The intent of this provision is to provide awarning should the HVAC system fail toprovide appropriate dilution ventilation air tomaintain user-defined indoor air qualitycriteria and acceptable concentrations.In DDC systems, for example, the computermight be set up to flag low airflow at anypoint in the system. In pneumatic systems,pressure sensors can be used. In some systemscarbon dioxide monitors may serve thepurposes of this provision. In small buildingswith very simple HVAC systems occupantscould report the status of air delivery in theirspaces: Air is not coming through the registertoday.The user can select a monitoring system thatmeets the needs of the building, the occupiedspace, the HVAC equipment, the financialsituation, and other local factors.A cognizant authority can be used to helpimplement this recommendation.329.11A monitoring system should be provided thatsignals an air quality-impairing malfunction ofthe HVAC system.33Note: Appendix sections are numbers based on themain text of this guideline.Supplementary materials are provided by Guidelinesection number. These materials are considered edu-cational and informational and are not part of theGuideline recommendations. A1. Dilution Ventilation The four most commonly used IAQ control approach-es are(1) dilution of airborne contaminants withfresh (or, less contaminated) air;(2) emission source control (which is closelyrelated to dilution);(3) treatment (filtration / scrubbing) andrecirculation of indoor air; and(4) identifying and improving confoundingfactors.Indoor air problems often are controlled with freshdilution air. An inadequate amount of dilution venti-lation allows background levels of air contaminantsto increase to unacceptable levels rather quickly inmost occupancies.For a constant emission source, no sinks, perfectmixing, and a constant airflow, the following equa-tion describes the resulting equilibrium concentrationin the ventilated space (e.g., chamber, room, build-ing):C=E/Qwhere E=emission rate and Q=ventilation rate inthe same units as E.Figure A1 shows the situation for five different emis-sion rates, all other conditions equal and at steady-state conditions. The numbers suggest ratios of emis-sion rates based on typical emission factors of 0.1 to5 mg/m2/hour. Note that background concentrationsincrease significantly at air exchange rates less thanN=0.5 ac/hour. Also, increases above 12 ac/hourdo not offer equivalent reductions in concentrations.Numerous studies have shown that when the OAsupply for dilution is less than 510 cfm/person,complaints and symptoms occur at rates in excess ofthose found in normal or healthy buildings. Studiesby EPA, NIOSH, ASHRAE, and the State ofWashington suggest the following normal com-plaint rates in healthy buildings. Comfort Issues: up to10% complaining of anyone thermal condition; up to 20%complaining of general thermal conditions Health Issues: 0% complaining of infectiousdiseases; 15% complaining ofasthma/allergies/multiple chemical sensitivity General, any or all IAQ complaints: up to20% complaining of any IAQ-related issueASHRAE 622001, in its Ventilation Rate Procedure(VRP), suggests 15 cfm/person as the minimum dilu-tion ventilation necessary to avoid complaints andodor problems. (Note: As of March 1, 2004, the VRPrate determination was in the process of beingchanged from a rate-per-person formula to rate-per-Appendix A: Supplementary InformationFigure A1.1. Air Exchange Rates and ExposureConcentrations (Source: H. Levin, IA Bulletin 3(5).1996.)Concentration (mg/m3)Air exchange rate (h-1)EF = 0.1EF = 0.5EF = 1EF = 1.5EF = 534person plus rate-per-floor-area formula.) ASHRAE622001 also suggested minimum rates of OA forvarious employee occupancies (e.g., 20 cfm/personin typical offices.) The VRP does not require muchevaluation of emission sources, but this may changeas the ASHRAE 61.2 standard is modified in thefuture.An alternative approach mentioned in ASHRAE 62.1is the indoor air quality procedure, which requires anevaluation of sources, emission rates, mixing effi-ciencies, and