Mitigating IAQ Problems
Over the years many types of mitigation indoor air contaminants change the (correction) strategies have been imple- relationships between these factors. There mented to solve indoor air quality prob- are many ways that people can intervene in 7 lems. The purpose of this section is to these relationships to prevent or control provide an understanding of basic ap- indoor air contaminant problems. Control proaches to mitigation and the various strategies can be categorized as: solutions that can be effective in treating n source control commonly-encountered IAQ problems. It n ventilation is not intended to provide detailed instruc- n air cleaning tions for using each type of mitigation n exposure control approach but rather to give guidance in selecting a mitigation strategy and in Successful mitigation often involves a judging proposals from in-house staff or combination of these strategies. Possible outside consultants. remedies for the other environmental Mitigation of indoor air quality prob- stressors discussed in Section 6 are lems may require the involvement of discussed briefly below. building management and staff represent- ing such areas of responsibility as: Source Control n facility operation and maintenance All efforts to prevent or correct IAQ n housekeeping problems should include an effort to n shipping and receiving identify and control pollutant sources. n purchasing Source control is generally the most cost n policymaking effective approach to mitigating IAQ n staff training problems in which point sources of contaminants can be identified. In the case Successful mitigation of IAQ problems of a strong source, source control may be also requires the cooperation of other the only solution that will work. building occupants, including the employ- The following are categories and ees of building tenants. Occupants must be examples of source control: educated about the cause(s) of the IAQ problems and about actions that must be Remove or reduce the source taken or avoided to prevent a recurrence of n prohibit smoking indoors or limit the problems. smoking to areas from which air is exhausted, not recirculated (NIOSH BACKGROUND: CONTROLLING regards smoking areas as an interim INDOOR AIR PROBLEMS solution) n relocate contaminant-producing equip- Section 2 introduced the idea that indoor ment to an unoccupied, better ventilated, air quality problems result from interac- or exhaust-only ventilated space tions between contaminant source, n select products which produce fewer or building site, building structure, activities less potent contaminants while maintain- within the building, mechanical equipment, ing adequate safety and efficacy climate, and occupants. Efforts to control
Mitigating IAQ Problems 81 n modify other occupant activities cannot be identified. Ventilation can be used to control indoor air contaminants by: Seal or cover the source n improve storage of materials that Diluting contaminants with outdoor air produce contaminants n increase the total quantity of supply air n seal surfaces of building materials that (including outdoor air) emit VOCs such as formaldehyde n increase the proportion of outdoor air to total air Modify the environment n improve air distribution n after cleaning and disinfecting an area that is contaminated by fungal or Isolating or removing contaminants by bacterial growth, control humidity to controlling air pressure relationships make conditions inhospitable for n install effective local exhaust at the regrowth location of the source n avoid recirculation of air that contains Source removal or reduction can contaminants sometimes be accomplished by a one-time n locate occupants near supply diffusers effort such as thorough cleaning of a spill. and sources near exhaust registers In other cases, it requires an ongoing n use air-tightening techniques to maintain process, such as establishing and enforcing pressure differentials and eliminate a non-smoking policy. pollutant pathways Sealing or covering the source can be a n make sure that doors are closed where solution in some cases; application of a necessary to separate zones barrier over formaldehyde-emitting building materials is an example. Sealing Diluting contaminants by increasing may also involve educating staff or the flow of outdoor air can be accom- building occupants about the contaminant- plished by increasing the total supply producing features of materials and airflow in the complaint area (e.g., opening supplies and inspecting storage areas to supply diffusers, adjusting dampers) or at ensure that containers are properly the air handling unit, (e.g., cleaning the covered. filter on the supply fan). An alternative is In some cases, modification of the to increase the proportion of outdoor air environment is necessary for effective (e.g., adjusting the outdoor air intake mitigation. If the indoor air problem damper, installing minimum stops on arises from microbiological contaminants, variable air volume (VAV) boxes so that for example, disinfection of the affected they satisfy the outdoor air requirements of area may not eliminate the problem. ASHRAE 62-1989). Regrowth of microbiologicals could Studies have shown that increasing occur unless humidity control or other ventilation rates to meet ASHRAE steps, such as adding insulation to prevent Standard 62-1989 (e.g., from 5 to 15 or 20 surface condensation, are taken to make cfm/person) does not necessarily signifi- the environment inhospitable to micro- cantly increase the total annual energy biologicals. consumption. The increase appears to be less than 5% in typical commercial Ventilation buildings. The cost of ventilation is generally overshadowed by other operating Ventilation modification is often used to costs, such as lighting. Further, improved correct or prevent indoor air quality maintenance can produce energy savings problems. This approach can be effective to balance the costs that might otherwise either where buildings are underventilated result from increased ventilation. or where a specific contaminant source
82 Section 7 The cost of modifying an existing Ventilation equipment can be used to HVAC system to condition additional isolate or contain contaminants by outdoor air can vary widely depending controlling pressure relationships. If the upon the specific situation. In some contaminant source has been identified, buildings, HVAC equipment may not have this strategy can be more effective than sufficient capacity to allow successful dilution. Techniques for controlling air mitigation using this approach. Original pressure relationships range from adjust- equipment is often oversized so that it can ment of dampers to installation of local be adjusted to handle the increased load, exhaust. but in some cases additional capacity is Using local exhaust confines the spread required. of contaminants by capturing them near the Most ventilation deficiencies appear to source and exhausting them to the out- be linked to inadequate quantities of doors. It also dilutes the contaminant by outdoor air. However, inadequate distribu- drawing cleaner air from surrounding areas tion of ventilation air can also produce into the exhaust airstream. If there are IAQ problems. Diffusers should be return grilles in a room equipped with local properly selected, located, installed, and exhaust, the local exhaust should exert maintained so that supply air is evenly enough suction to prevent recirculation of distributed and blends thoroughly with contaminants. Properly designed and room air in the breathing zone. Short- installed local exhaust results in far lower circuiting occurs when clean supply air is contaminant levels in the building than drawn into the return air plenum before it could be accomplished by a general has mixed with the dirtier room air and increase in dilution ventilation, with the therefore fails to dilute contaminants. added benefit of costing less. Mixing problems can be aggravated by Note that replacement air must be able temperature stratification. Stratification to flow freely into the area from which the can occur, for example, in a space with exhaust air is being drawn. It may be high ceilings in which ceiling-mounted necessary to add door or wall louvers in supply diffusers distribute heated air. order to provide a path for the make-up air. Note the side effects of increased (Make sure that this action does not violate ventilation: fire codes.) n mitigation by increasing the circulation Correct identification of the pollutant of outdoor air requires good outdoor air source and installation of the local exhaust quality is critically important. For example, an n increased supply air at the problem improperly designed local exhaust can location might mean less supply air in draw other contaminants through the other areas occupied space and make the problem n increased total air in the system and worse. increased outdoor air will both tend to The physical layout of grilles and increase energy consumption and may diffusers relative to room occupants and require increased equipment capacity pollutant sources can be important. If n any approach which affects airflow in supply diffusers are all at one end of a the building can change pressure room and returns are all at the other end, differences between rooms (or zones) the people located near the supplies may and between indoors and outdoors, and be provided with relatively clean air while might lead to increased infiltration of those located near the returns breathe air unconditioned outdoor air that has already picked up contaminants n increasing air in a VAV system may from all the sources in the room that are overcool an area to the extent that not served by local exhaust. terminal reheat units are needed
Mitigating IAQ Problems 83 Elimination of pollutant pathways by air The first three approaches are designed sealing (e.g., caulking cracks, closing to remove particulates, while the fourth is holes) is an approach that can increase the designed to remove gases. effectiveness of other control techniques. Particulate filtration removes sus- It can be a difficult technique to implement pended liquid or solid materials whose because of hidden pathways (e.g., above size, shape and mass allow them to remain drop ceilings, under raised flooring airborne for the air velocity conditions against brick or block walls). However, it present. Filters are available in a range of can have other benefits such as energy efficiencies, with higher efficiency indicat- savings and more effective pest control (by ing removal of a greater proportion of eliminating paths used by vermin). particles and of smaller particles. Moving to medium efficiency pleated filters is Air Cleaning advisable to improve IAQ and increase The third IAQ control strategy is to clean protection for equipment. However, the the air. Air cleaning is usually most effec- higher the efficiency of the filter, the more tive when used in conjunction with either it will increase the pressure drop within the source control or ventilation; however, it air distribution system and reduce total may be the only approach when the source airflow (unless other adjustments are made of pollution is outside of the building. to compensate). It is important to select an Most air cleaning in large buildings is appropriate filter for the specific aimed primarily at preventing contaminant application and to make sure that the buildup in HVAC equipment and enhanc- HVAC system will continue to perform as ing equipment efficiency. designed. Filters are rated by different Air cleaning equipment intended to standards (e.g., arrestance and dust spot) provide better indoor air quality for occu- which measure different aspects of pants must be properly selected and de- performance. signed for the particular pollutants of inter- Electrostatic precipitation is another est (for example, gaseous contaminants can type of particulate control. It uses the be removed only by gas sorption). Once attraction of charged particles to oppo- installed, the equipment requires regular sitely charged surfaces to collect airborne maintenance in order to ensure good per- par-ticulates. In this process, the particles formance; otherwise it may become a are charged by ionizing the air with an major pollutant source in itself. This main- electric field. The charged particles are tenance requirement should be borne in then col-lected by a strong electric field mind if an air cleaning system involving a generated between oppositely-charged large number of units is under consider- electrodes. This provides relatively high ation for a large building. If room units are efficiency filtration of small respirable used, the installation should be designed particles at low air pressure losses. for proper air recirculation. Electrostatic precipitators may be in- There are four technologies that remove stalled in air distribution equipment or in contaminants from the air: specific usage areas. As with other filters, they must be serviced regularly. Note, n particulate filtration however, that electrostatic precipitators n electrostatic precipitation produce some ozone. Because ozone is n negative ion generation harmful at elevated levels, EPA has set n gas sorption standards for ozone concentrations in out- door air, and NIOSH and OSHA have
84 Section 7 established guidelines and standards, re- Scheduling contaminant-producing acti- spectively, for ozone in indoor air. The vities to avoid complaints amount of ozone emitted from electrostatic n schedule contaminant-producing activi- precipitators varies from model to model. ties to occur during unoccupied periods Negative ion generators use static n notify susceptible individuals about up- charges to remove particles from the indoor coming events (e.g., roofing, pesticide air. When the particles become charged, application) so that they can avoid contact they are attracted to surfaces such as walls, with the contaminants floors, table tops, draperies, and occupants. Scheduling contaminant-producing ac- Some designs include collectors to attract tivities for unoccupied periods whenever the charged particles back to the unit. possible is simple common sense. It may Negative ion generators are not available be the best way to limit complaints about for installation in ductwork, but are sold as activities (such as roofing or demolition) portable or ceiling-mounted units. As with which unavoidably produce odors or dust. electrostatic precipitators, negative ion generators may produce ozone, either Relocating susceptible individuals inten-tionally or as a by-product of use. n move susceptible individuals away from the area where they experience symptoms Gas sorption is used to control com- pounds that behave as gases rather than as Controlling exposure by relocating sus- particles (e.g., gaseous contaminants such ceptible individuals may be the only practi- as formaldehyde, sulfur dioxide, ozone, and cal approach in a limited number of cases, oxides of nitrogen). Gas sorption involves but it is probably the least desirable option one or more of the following processes and should be used only when all other with the sorption material (e.g., activated strategies are ineffective in resolving com- carbon, chemically treated active clays): a plaints. chemical reaction between the pollutant and the sorbent, a binding of the pollutant Remedies for Complaints Not and the sorbent, or diffusion of the con- Attributed to Poor Air Quality taminant from areas of higher concentration Specific lighting deficiencies or localized to areas of lower concentration. Gas sorp- sources of noise or vibration can sometimes tion units are installed as part of the air be readily identified, and remedial action distribution system. Each type of sorption may be fairly straightforward (more or material performs differently with different fewer lights on, adjustments for glare; relo- gases. Gas sorption is not effective for cating, replacing or acoustically insulating a removing carbon monoxide. There are no noise or vibration source). Similarly, fla- standards for rating the performance of grant ergonomic stress or blatant psycho- gaseous air cleaners, making the design and social stress may be apparent even to evaluation of such systems problematic. an untrained observer. Operating expenses of these units can be In other cases, however, problems may quite high, and the units may not be effec- be more subtle or solutions more complex. tive if there is a strong source nearby. Since specialized knowledge, skills, and instrumentation are usually needed to Exposure Control evaluate lighting, noise, vibration, ergo- Exposure control is an administrative ap- nomic stress, or psychosocial stress, such proach to mitigation that uses behavioral evaluations are generally best done by a methods, such as: qualified professional in that particular field.
Mitigating IAQ Problems 85 Remedial actions for lighting, noise, that each solution listed would be an and vibration problems might range from effective treatment for all of the problems modifications of equipment or furnishings in its category. to renovation of the building. Ergonomic The example problems and solutions are deficiencies may require furniture or presented in the following sequence: equipment changes or different work Problem #1: Outdoor air ventilation rate practices. The solution to psychosocial is too low problems may involve new management practices, job redesign, or resolution of Problem #2: Overall ventilation rate is underlying labor-management problems. high enough, but poorly distributed and not sufficient in some areas SAMPLE PROBLEMS AND SOLUTIONS Problem #3: Contaminant enters building In the investigation section you were from outdoors introduced to a variety of problems that are Problem #4: Occupant activities contrib- often found in buildings. This section ute to air contaminants or to presents fifteen categories of IAQ prob- comfort problems lems. Specific problem “examples” are Problem #5: HVAC system is a source of given, followed by solutions” that have biological contaminants been used for that category of problem. Problem #6: HVAC system distributes Most of the problems presented here are contaminants common and do not have serious, life- Problem #7: Non-HVAC equipment is a threatening consequences. At the end of source or distribution mecha- the section is a brief description of nism for contaminants problems that can have severe health Problem #8: Surface contamination due to impacts. The basic correction principles poor sanitation or accidents that apply to these serious problems are similar to those used in less critical Problem #9: Mold and mildew growth situations. due to moisture from con- Reading these examples may help you densation to think about the best way to solve your Problem #10: Building materials and indoor air quality problems. Remember furnishings produce that these are brief sketches, and apparent contaminants parallels to your building could be mis- Problem #11: Housekeeping or mainte- leading. It is better to carry out a building nance activities contribute to investigation and learn the specific facts in problems your own case, rather than adopt a mitiga- Problem #12: Specialized use areas as tion approach that might not be appropri- sources of contaminants ate. Attempting to correct IAQ problems Problem #13: Remodeling or repair activi- without understanding the cause of those ties produce problems problems can be both ineffective and Problem #14: Combustion gases expensive. You will note that some solutions are Problem #15: Serious building-related simple and low-cost, while others are illness complex and expensive. Do not assume
86 Section 7 Problem #1: Outdoor Air Ventilation Rate is Too Low
Examples Routine odors from occupants and normal office activities result in problems (e.g., drowsiness, headaches, discomfort) Measured outdoor air ventilation rates do not meet guidelines for outdoor air supply (e.g., design specifications, applicable codes, or ASHRAE 62-1989)
Peak CO2 concentrations above 1000 ppm indicate inadequate ventilation Corrosion of fan casing causes air bypassing and reduces airflow in system
Solutions Open, adjust or repair air distribution system n outdoor air intakes n mixing and relief dampers n supply diffusers n fan casings Malfunctioning controls such as this broken Increase outdoor air within the design damper linkage can virtually eliminate capacity of intake of outdoor air. Such problems may go undetected for years without a careful n air handler investigation of the HVAC system n heating and air conditioning equipment components. n distribution system Modify components of the HVAC system as needed to allow increased outdoor air (e.g., increase capacity of heating and cooling coils) Design and install an updated ventilation system Reduce the pollutant and/or thermal load on the HVAC system n reduce the occupant density: relocate some occupants to other spaces to redistribute the load on the ventilation system n relocate or reduce usage of heat- generating equipment
Mitigating IAQ Problems 87 Problem #2: Examples Overall Ventilation Rate Is Measured outdoor air meets guidelines at High Enough, But Poorly building air inlet, but there are zones Distributed and Not where heat, routine odors from occu- Sufficient in Some Areas pants, and normal office activities result in complaints (e.g., drowsiness, headaches, comfort complaints)
Solutions Open, adjust, or repair air distribution system
n supply diffusers n return registers Ensure proper air distribution
n balance the air handling system n make sure that there is an air gap at tops and bottoms of partitions to prevent dead air space n relocate supply and/or return diffusers to improve air distribution Seal leaky ductwork Remove obstructions from return air plenum Control pressure relationships
n install local exhaust in problem areas Complaining of discomfort, building and adjust HVAC system to provide occupants blocked air supply diffusers in adequate make-up air their work areas. The HVAC system in this building was in poor condition and was not n move occupants so that they are closer to balanced. supply diffusers n relocate identified contaminant sources closer to exhaust intakes Reduce source by limiting activities or equipment use that produce heat, odors, or contaminants Design and install an appropriate ventilation system
88 Section 7 Problem #3: Contaminant Entering Building From Outdoors
Examples Soil gases (e.g., radon, gasoline from tanks, methane from landfills) Contaminants from nearby activities (e.g., roofing, dumpster, construction) Outdoor air intake near source (e.g., parking, loading dock, building exhaust) Outdoor air contains pollutants or excess moisture (e.g., cooling tower mist entrained in outdoor air intake)
Solutions Remove the source, if it can be moved easily n remove debris around outdoor air intake n relocate dumpster Reduce source (for example, shift time of activity to avoid occupied periods) Change air pressure relationships to For cosmetic reasons, air intakes are frequently located n painting, roofing, demolition control pollutant pathways on rooftops or near the n housekeeping, pest control n install subslab depressurization to ground. This air intake could prevent entry of soil gas contaminants become a means of drawing Relocate elements of the ventilation lawn cuttings, vehicle system that contribute to entry of outdoor (radon, gases from landfills and under- exhaust, and pesticides into air contaminants ground tanks) the building. n pressurize the building interior relative to n separate outdoor air intakes from sources outdoors (this will not prevent contami- of odors, contaminants nant entry at outdoor air intakes) n separate exhaust fan outlets from n close pollutant pathways (e.g., seal operable windows, doors, air intakes cracks and holes) n make rooftop exhaust outlets taller than intakes Add special equipment to HVAC system
n filtration equipment to remove pollutants (select to fit the situation)
Mitigating IAQ Problems 89 Problem #4: Examples Occupant Activities Smoking Contribute to Air Contaminants or to Special activities such as print shops, Comfort Problems laboratories, kitchens Interference with HVAC system operation:
n blockage of supply diffusers to eliminate drafts n turning off exhaust fans to eliminate noise n use of space heaters, desktop humidifiers to remedy local discomfort (Note: While such interference can cause IAQ problems, it is often initiated in response to unresolved ventilation or temperature control problems.)
Solutions Remove the source by eliminating the activity (Note: This may require a combination of policy-setting and educational outreach.)
n smoking n use of desktop humidifiers and other personal HVAC equipment n unsupervised manipulation of HVAC system Reduce the source n select materials and processes which Personal equipment such as humidifiers minimize release of contaminants while brought in by building occupants can maintaining adequate safety and efficacy become a source of contaminants if not properly maintained. An effective (e.g., solvents, art materials) communication strategy can help occupants to understand their role in Install new or improved local exhaust to causing indoor air quality problems and in accommodate the activity, adjust HVAC correcting those problems. system to ensure adequate make-up air, and verify effectiveness
n smoking lounge, storage areas which contain contaminant sources n laboratory hoods, kitchen range hoods (venting to outdoors, not recirculating)
90 Section 7 Problem #5: HVAC System is a Source of Biological Contaminants The HVAC system can act as a source of contaminants by providing a hospitable environment for the growth of microorgan- isms and by then distributing biologically- contaminated air within the building.
Examples Surface contamination by molds (fungi), bacteria n drain pans n interior of ductwork n air filters and filter media (collected debris).
Solutions Remove source by improving mainte- nance procedures n inspect equipment for signs of corrosion, high humidity n replace corroded parts n clean drip pans, outdoor air intakes, other affected locations This blackish deposit was scraped from a poorly-maintained air handling unit drain n use biocides, disinfectants, and sanitizers pan. The pan contained nutrients caused with extreme caution and ensure that by poor upstream filtration and stagnant occupant exposure is minimized water that fostered the growth of (Note: See discussion of duct cleaning in microbiological contaminants. Appendix B.) Provide access to all the items that must be cleaned, drained, or replaced periodically
Mitigating IAQ Problems 91 Problem #6: Examples HVAC System Distributes Unfiltered air bypasses filters due to Contaminants problems
n filter tracks are loose n poorly-maintained filters sag when they become overloaded with dirt n filters are the wrong size Recirculation of air that contains dust or other contaminants
n system recirculates air from rooms containing pollutant sources n return air plenum draws air from rooms that should be exhausted (e.g. janitor’s closets) n return air plenums draw soil gases from interiors of block corridor walls that terminate above ceilings
Solutions Modify air distribution system to minimize recirculation of contaminants
n provide local exhaust at point sources of contaminants, adjust HVAC system to provide adequate make-up air, and test to verify performance n increase proportion of outdoor air n seal unplanned openings into return air plenums and provide alternative local ventilation (adjust HVAC system to Standing water on a roof can cause water damage and potential mold growth sites provide adequate make-up air and test to inside the building as well as providing a verify performance) breeding area for insects and microbiologicals such as Legionella. The Improve housekeeping, pest control, outside air intake (near the far left of this occupant activities, and equipment use to photograph) is located close to the minimize release of contaminants from standing water and could be drawing in insects and microbiological contaminants. all sources Install improved filtration equipment to remove contaminants Check filter tracks for any gaps
92 Section 7 Problem #7: Non-HVAC Equipment is a Source or Distribution Mechanism for Contaminants
This discussion pertains to medium- to large-scale pieces of equipment.
Examples Non-HVAC equipment can produce contaminants, as in the case of: n wet process copiers n large dry process copiers n engineering drawing reproduction machines It can also distribute contaminants, as in the case of: n elevators, which can act as pistons and draw contaminants from one floor to another
Solutions Install local exhaust near machines (Note: Adjust HVAC system to provide adequate make-up air, and test to verify performance.) Sometimes there are unusual sources of indoor air quality problems. An inspection Reschedule use to occur during periods of of the HVAC system revealed air filters low occupancy covered with a graphite dust deposit from a broken elevator motor generator. The Remove source motor generator was repaired and corrections were made to prevent the n relocate occupants out of rooms crossover of ventilation air from the motor that contain contaminant-generating generator into the HVAC mechanical room. equipment n relocate equipment into special use areas equipped with effective exhaust ventilation (test to verify control of air pressure relationships) Change air pressure relationships to prevent contaminants from entering elevator shaft
Mitigating IAQ Problems 93 Problem #8: Examples Surface Contamination Biological contaminants result in aller- Due to Poor Sanitation or gies or other diseases Accidents n fungal, viral, bacterial (whole organisms or spores) n bird, insect, or rodent parts or droppings, hair, dander (in HVAC, crawlspace, building shell, or near outdoor air intakes) Accidents
n spills of water, beverages, cleansers, paints, varnishes, mastics or specialized products (printing, chemical art supplies) n fire damage: soot, odors, chemicals
Solutions Clean
n HVAC system components n some materials and furnishings (others may have to be discarded) (Note: Use biocides, disinfectants, and sanitizers with caution and ensure that occupant exposure is minimized.) Remove sources of microbiological contamination
n water-damaged carpet, furnishings, or building materials Modify environment to prevent recur- The carpet on this floor was flooded and an outbreak of humidifier fever rence of microbiological growth occurred. To eliminate microbiologicals, n improve HVAC system maintenance the contaminated carpet was removed and new carpet was installed. n control humidity or surface temperatures to prevent condensation Provide access to all items that require periodic maintenance Use local exhaust where corrosive materials are stored Adjust HVAC system to provide adequate make-up air, and test to verify perfor- mance
94 Section 7 Problem #9: Mold and Mildew Growth Due to Moisture from Condensation
Examples Interior surfaces of walls near thermal bridges (e.g., uninsulated locations around struc- tural members) Carpeting on cold floors Locations where high surface humidity promotes condensation
Solutions Clean and disinfect to remove mold and mildew. (Note: Follow up by taking actions to prevent recurrence of microbiological contamination. Use biocides, disinfec- tants, and sanitizers with caution and ensure that occupant exposure is mini- mized.)
Increase surface temperatures to treat This is a school crawlspace in which locations that are subject to condensation moisture should be controlled. The fungus is Fusarium, some species of which are n insulate thermal bridges toxigenic and should not be inside. The n improve air distribution spores were distributed by the air handler because the return plenum was open to the crawlspace. Reduce moisture levels in locations that are subject to condensation n repair leaks n increase ventilation (in cases where outdoor air is cold and dry) n dehumidify (in cases where outdoor air is warm and humid) Dry carpet or other textiles promptly after steam cleaning (Note: Increase ventilation to accelerate drying.) Discard contaminated materials
Mitigating IAQ Problems 95 Problem #10: Examples Building Materials and Odors from newly installed carpets, Furnishings Produce furniture, wall coverings Contaminants Newly drycleaned drapes or other textiles
Solutions Remove source with appropriate cleaning methods
n steam clean carpeting and upholstery, then dry quickly, ventilating to acceler- ate the drying process n accept only fully dried, odorless drycleaned products Encapsulate source
n seal surfaces of building materials that emit formaldehyde Reduce source
n schedule installation of carpet, furniture, and wall coverings to occur during periods when the building is unoccupied n have supplier store new furnishings in a clean, dry, well-ventilated area until VOC outgassing has diminished Increase outdoor air ventilation
n total air supplied n proportion of fresh air Remove the materials that are producing the emissions and replace with lower Low levels of contaminants are emitted from many of the building materials emission alternatives and furnishings in an office. Dust can (Note: Only limited information on accumulate on stacks of papers and emissions from materials is available at open shelves. Depending on how they are cared for, plants potentially this time. Purchasers can request that add moisture, soil microbiologicals, suppliers provide emissions test data, but and pesticides. should use caution in interpreting the test results.)
96 Section 7 Problem #11: Housekeeping or Maintenance Activities Contribute to Problems
Examples Cleaning products emit chemicals, odors Particulates become airborne during cleaning (e.g., sweeping, vacuuming) Contaminants are released from painting, caulking, lubricating Frequency of maintenance is insufficient to eliminate contaminants
Solutions Remove source by modifying standard procedures or frequency of maintenance (Note: Changing procedures may require a combination of policy-setting and training in IAQ impacts of staff activities.) n improve storage practices n shift time of painting, cleaning, pest control, other contaminant-producing activities to avoid occupied periods Indoor air quality problems can be caused by lack of adequate house-keeping n make maintenance easier by improving practices. On the other hand, deodorizers, access to filters, coils, and other compo- cleansers and other products can also nents produce odors and contaminants. Reduce source n select materials to minimize emissions of contaminants while maintaining ad- equate safety and efficacy n use portable HEPA (high efficiency particulate arrestance”) vacuums vs. low- efficiency paper-bag collectors Use local exhaust n on a temporary basis to remove contami- nants from work areas n as a permanent installation where contaminants are stored
Mitigating IAQ Problems 97 Problem #12: Examples Specialized Use Areas as Food preparation Sources of Contaminants Art or print rooms Laboratories
Solutions Change pollutant pathway relationships
n run specialized use area under negative pressure relative to surrounding areas n install local exhaust, adjust HVAC system to provide make-up air, and test to verify performance Remove source by ceasing, relocating, or rescheduling incompatible activities Reduce source by selecting materials to minimize emissions of contaminants while maintaining adequate safety and efficacy Reduce source by using proper sealing and storage for materials that emit contaminants
This chemical storage room should be maintained under negative pressure. Properly designed and maintained local exhaust will achieve the proper air pressure relationship with surrounding areas. Otherwise, such storage areas can be a source of occupant exposure to many airborne contaminants.
98 Section 7 Problem #13: Remodeling or Repair Activities Produce Problems
Examples Temporary activities produce odors and contaminants n installation of new particleboard, partitions, carpet, or furnishings n painting n reroofing n demolition Existing HVAC system does not provide adequate ventilation for new occupancy or arrangement of space
Solutions Modify ventilation to prevent recircula- tion of contaminants n install temporary local exhaust in work area, adjust HVAC system to provide make-up air, and test to verify performance n seal off returns in work area n close outdoor air damper during re-roofing Modify HVAC or wall partition layout if Remodeling may involve necessary many activities that can Reduce source by scheduling work for cause IAQ problems. unoccupied periods and keeping ventila- n partitions should not interrupt airflow Ventilation modifications can tion system in operation to remove odors n relocate supply and return diffusers be used to isolate the work area and prevent pollutant n adjust supply and return air quantities and contaminants build-up in occupied spaces. n adjust total air and/or outdoor air supply Reduce source by careful materials Proper storage practices can to serve new occupancy minimize the release of selection and installation contaminants. n select materials to minimize emissions of contaminants while maintaining adequate safety and efficacy n have supplier store new furnishings in a clean, dry, well-ventilated area until VOC outgassing has diminished n request installation procedures (e.g., adhesives) that limit emissions of contaminants
Mitigating IAQ Problems 99 Problem #14: Examples Combustion Gases Vehicle exhaust
n offices above (or connected to) an Combustion odors can indicate the underground parking garage existence of a serious problem. One n rooms near (or connected by pathways combustion product, carbon monoxide, is to) a loading dock or service garage an odorless gas. Carbon monoxide poisoning can be life-threatening. Combustion gases from equipment (e.g., spillage from inadequately vented appliances, cracked heat exchanger, re- entrainment because local chimney is too low)
n areas near a mechanical room n distributed throughout zone or entire building
Solutions Seal to remove pollutant pathway
n close openings between the contaminant source and the occupied space n install well-sealed doors with automatic closers between the contaminant source and the occupied space Remove source
n improve maintenance of combustion equipment n modify venting or HVAC system to prevent backdrafting n relocate holding area for vehicles at loading dock, parking area n turn off engines of vehicles that are waiting to be unloaded Modify ventilation system
n install local exhaust in underground parking garage (adjust HVAC system to Air intakes are frequently located near the provide make-up air and test to verify loading dock for aesthetic reasons. performance) Unfortunately, this air intake placement can draw car and truck exhaust into the n relocate fresh air intake (move away building, causing a variety of indoor air from source of contaminants quality complaints. Modify pressure relationships
n pressurize spaces around area containing source of combustion gases
100 Section 7 Problem #15: Serious Building-Related Illness
Some building-related illnesses can be life- threatening. Even a single confirmed diagnosis (which involves results from specific medical tests) should provoke an immediate and vigorous response.
Examples Legionnaire’s disease (Note: If you suspect Legionnaire’s disease, call the local public health department, check for obvious problem sites, and take corrective action. There is no way to be certain that a single case of this disease is associated with building occupancy; therefore, public health agencies usually do not investigate single cases. Watch for new cases.) Hypersensitivity pneumonitis n install drip pans that drain properly This air intake is located n provide access to all the items that must between the cooling towers. (Note: Affected occupant(s) should be If the water in the cooling removed and may not be able to return be cleaned, drained, or replaced periodi- towers becomes unless the causative agent is removed from cally contaminated with Legionella, there is potential for the affected person’s environment.) n modify schedule and procedures for improved maintenance Legionnaire’s disease in the building. Solutions Discontinue processes that deposit Work with public health authorities potentially contaminated moisture in air n evacuation may be recommended or distribution system
required n air washing Remove source n humidification n cease nighttime shutdown of air handlers n drain, clean, and decontaminate drip pans, cooling towers, room unit air conditioners, humidifiers, dehumidifiers, and other habitats of Legionella, fungi, and other organisms using appropriate protective equipment
Mitigating IAQ Problems 101 JUDGING PROPOSED situation worse (unless the outdoor air is MITIGATION DESIGNS cleaned). AND THEIR SUCESS Degree to Which the Strategy Mitigation efforts should be evaluated at Fits the Job the planning stage by considering the following criteria: It is important to make sure that you
n permanence understand the IAQ problem well enough n operating principle to select a correction strategy whose size The most economical n degree to which the strategy fits the job and scope fit the job. If odors from a special use area such as a kitchen are and successful n ability to institutionalize the solution causing complaints in a nearby office, solutions to IAQ n durability n installation and operating costs increasing the ventilation rate in the office problems are those n conformity with codes may not be a successful approach. The in which the operat- mitigation strategy should address the ing principle of the Permanence entire area affected. correction strategy If mechanical equipment is needed to Mitigation efforts that create permanent makes sense and is correct the IAQ problem, it must be solutions to indoor air problems are clearly powerful enough to accomplish the task. suited to the prob- superior to those that provide temporary For example, a local exhaust system lem. solutions (unless the problems are also should be strong enough and close enough temporary). Opening windows or running to the source so that none of the contami- air handlers on full outdoor air may be nant is drawn into nearby returns and suitable mitigation strategies for a tempo- recirculated. rary problem such as outgassing of volatile compounds from new furnishings, but Ability to Institutionalize would not be good ways to deal with the Solution emissions from a print shop. A permanent solution to microbiological contamination A mitigation strategy will be most success- involves not only cleaning and disinfec- ful when it is institutionalized as part of tion, but also modification of the environ- normal building operations. Solutions that ment to prevent regrowth. do not require exotic equipment are more likely to be successful in the long run than Operating Principle approaches that involve unfamiliar concepts or delicately maintained systems. The most economical and successful If maintenance or housekeeping proce- solutions to IAQ problems are those in dures or supplies must change as part of which the operating principle of the the mitigation, it may be necessary to plan correction strategy makes sense and is for additional staff training, new inspection suited to the problem. If a specific point checklists, or modified purchasing prac- source of contaminants has been identified, tices. Operating schedules for HVAC treatment at the source (e.g., by removal, equipment may also require modification. sealing, or local exhaust) is almost always a more appropriate correction strategy than Durability dilution of the contaminant by increased general ventilation. If the IAQ problem is IAQ mitigation strategies that are durable caused by the introduction of outdoor air and low-maintenance are more attractive to that contains contaminants, increased owners and building staff than approaches general ventilation will only make the that require frequent adjustment or
102 Section 7 specialized maintenance skills. New items of equipment should be quiet, energy- efficient, and durable, so that the operators MANAGING MITIGATION PROJECTS are encouraged to keep them running. INVOLVING SEVERE CONTAMINATION
Elements Cautions Installation and Operating Costs Identify the extent of contami- Locating the original source of a chemi- The approach with the lowest initial cost nation cal release or microbiological growth may only be the tip of the iceberg. may not be the least expensive over the Pollutants often tend to migrate through long run. Other economic considerations a building and collect in “sinks”, from include: energy costs for equipment opera- which they can be resuspended into the tion, increased staff time for maintenance; air. For example, particles accumulate differential cost of alternative materials on horizontal surfaces that are not and supplies; and higher hourly rates if subject to regular housekeeping; odors may adsorb (stick) to porous materials. odor-producing activities (e.g., cleaning) Detailed surface and/or bulk sampling must be scheduled for unoccupied periods. may be needed to locate such “second- Although these costs will almost certainly ary” sources in order to solve an air be less than the cost of letting the problem quality problem. continue, they are more readily identifi- able, so an appropriate presentation to Depending on the problem, a detailed management may be required. Develop a precise scope of work specifying exactly how knowledge of chemistry, microbiology, remediation will be performed building science, and health and safety Conformity with Codes may be required. Any modification to building components Monitor remediation to ensure Include air sampling along with regular or mechanical systems should be designed work practices are followed inspections if needed. Decontamination and installed in keeping with applicable of areas within an occupied building is fire, electrical, and other building codes. especially critical.
Conduct clearance In the event of severe contamination, Judging the Success of a sampling representative air samples should be Mitigation Effort collected to ensure that key indicators have returned to background levels and Two kinds of criteria can be used to judge that the space can be safely reoccupied. the success of an effort to correct an indoor air problem: n reduced complaints n measurement of properties of the indoor Many routine IAQ problems can be air (often only of limited usefulness) corrected by a common sense approach not requiring special expertise. However, when complex exposure or contamination Reduction or elimination of complaints issues are involved, more detailed techni- appears to be a clear indication of success, cal assistance may be needed for success- but that is not necessarily the case. ful remediation. Efforts such as those Occupants who see that their concerns are outlined above are sometimes needed to being heard may temporarily stop report- deal with severe contamination. ing discomfort or health symptoms, even if the actual cause of their complaints has not been addressed. Lingering complaints may also continue after successful mitigation if people have become upset over the
Mitigating IAQ Problems 103 handling of the problem. Ongoing (but hypothesis testing. Deeper and more reduced) complaints could also indicate detailed investigation is needed to suggest that there were multiple IAQ problems and new hypotheses after any unsuccessful or that one or more problems are still unre- partially-successful control attempt. solved. Even the best-planned investigations If you have made However, it can be very difficult to use and mitigation actions may not produce a several unsuccessful measurements of contaminant levels as a resolution to the problem. You may have efforts to control a means of determining whether air quality made a careful investigation, found one or has improved. Concentrations of indoor more apparent causes for the problem, and problem, then it may air pollutants typically vary greatly over implemented a control system. Nonethe- be advisable to seek time; further, the specific contaminant less, your correction strategy may not have outside assistance. measured may not be causing the problem. caused a noticeable reduction in the If air samples are taken, readings taken concentration of the contaminant or before and after mitigation should be improvement in ventilation rates or interpreted cautiously. It is important to efficiency. Worse, the complaints may keep the “before” and “after” conditions as persist even though you have been identical as possible, except for the successful at improving ventilation and operation of the control strategy. For controlling all of the contaminants you example, the same HVAC operation, could identify. When you have pursued building occupancy and climatic condi- source control options and have increased tions should apply during both measure- ventilation rates and efficiency to the limits ment periods. “Worst-case” conditions of your expertise, you must decide how identified during the investigation should important it is to pursue the problem be used. further. Measurements of airflows, ventilation If you have made several unsuccessful rates, and air distribution patterns are the efforts to control a problem, then it may be more reliable methods of assessing the advisable to seek outside assistance. The results of control efforts. Airflow mea- problem is probably fairly complex, and it surements taken during the building may occur only intermittently or cross the investigation can identify areas with poor borders that divide traditional fields of ventilation; later they can be used to knowledge. It is even possible that poor evaluate attempts to improve the ventila- indoor air quality is not the actual cause of tion rate, distribution, or direction of flow. the complaints. Bringing in a new Studying air distribution patterns will show perspective at this point can be very whether a mitigation strategy has success- effective. fully prevented a contaminant from being The next section provides guidance on transported by airflow. hiring professional indoor air quality assistance. An interdisciplinary team (such Persistent Problems as people with engineering and medical or health backgrounds) may be needed to Solving an indoor air quality problem is a solve particularly difficult problems. cyclical process of data collection and
104 Section 7