Issue link: https://hi.iaq.net/i/630729
82 Section 7 ■ modify other occupant activities Seal or cover the source ■ improve storage of materials that produce contaminants ■ seal surfaces of building materials that emit VOCs such as formaldehyde Modify the environment ■ after cleaning and disinfecting an area that is contaminated by fungal or bacterial growth, control humidity to make conditions inhospitable for regrowth Source removal or reduction can sometimes be accomplished by a one-time effort such as thorough cleaning of a spill. In other cases, it requires an ongoing process, such as establishing and enforcing a non-smoking policy. Sealing or covering the source can be a solution in some cases; application of a barrier over formaldehyde-emitting building materials is an example. Sealing may also involve educating staff or building occupants about the contaminant- producing features of materials and supplies and inspecting storage areas to ensure that containers are properly covered. In some cases, modification of the environment is necessary for effective mitigation. If the indoor air problem arises from microbiological contaminants, for example, disinfection of the affected area may not eliminate the problem. Regrowth of microbiologicals could occur unless humidity control or other steps, such as adding insulation to prevent surface condensation, are taken to make the environment inhospitable to micro- biologicals. Ventilation Ventilation modification is often used to correct or prevent indoor air quality problems. This approach can be effective either where buildings are underventilated or where a specific contaminant source cannot be identified. Ventilation can be used to control indoor air contaminants by: Diluting contaminants with outdoor air ■ increase the total quantity of supply air (including outdoor air) ■ increase the proportion of outdoor air to total air ■ improve air distribution Isolating or removing contaminants by controlling air pressure relationships ■ install effective local exhaust at the location of the source ■ avoid recirculation of air that contains contaminants ■ locate occupants near supply diffusers and sources near exhaust registers ■ use air-tightening techniques to maintain pressure differentials and eliminate pollutant pathways ■ make sure that doors are closed where necessary to separate zones Diluting contaminants by increasing the flow of outdoor air can be accom- plished by increasing the total supply airflow in the complaint area (e.g., opening supply diffusers, adjusting dampers) or at the air handling unit, (e.g., cleaning the filter on the supply fan). An alternative is to increase the proportion of outdoor air (e.g., adjusting the outdoor air intake damper, installing minimum stops on variable air volume (VAV) boxes so that they satisfy the outdoor air requirements of ASHRAE 62-1989). Studies have shown that increasing ventilation rates to meet ASHRAE Standard 62-1989 (e.g., from 5 to 15 or 20 cfm/person) does not necessarily signifi- cantly increase the total annual energy consumption. The increase appears to be less than 5% in typical commercial buildings. The cost of ventilation is generally overshadowed by other operating costs, such as lighting. Further, improved maintenance can produce energy savings to balance the costs that might otherwise result from increased ventilation.