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December 20, 2012 -
Today's tip from Building Operating Management is to control sources of indoor pollutants to safeguard indoor air quality. Rather than making the HVAC system the first line of defense, try to control pollutant sources locally. Localizing large pollutant contributors in separate rooms is an effective method of controlling contamination. These rooms should be maintained under negative pressure in relation to surrounding rooms and exhausted directly to the outdoors. Large contributors include photocopier rooms or special process print rooms.
Contaminant sensing can be used as a means to ensure there is adequate ventilation. In areas of a building where occupancy or contaminant levels are variable, consider the use of carbon dioxide, volatile organic compound, carbon monoxide or other contaminant-sensing inputs. HVAC systems can use the information from the contaminant-sensing inputs to control the amount of outdoor air introduced into an area within a building. When contaminant level thresholds are exceeded and the system calls for increased ventilation, precautions should be made that the outdoor air being brought in isn't itself contaminated.
You might also consider a night purge cycle. HVAC systems can often be programmed to operate on a night "flush" cycle on 100 percent outside air to clear out any unwanted indoor pollutants on a daily basis. However, this strategy is not advisable when the outside air is especially warm, humid or contaminated.
A good filtration system will also play a key role in preserving indoor air quality, even with these other measures in place. When possible, design or retrofit HVAC systems to incorporate high-efficiency filters. Some filtrations strategies to consider include:
- Consider upgrading filtration with a 30 percent ASHRAE prefilter and a 90 percent ASHRAE final filter, but first make sure the system can handle the additional pressure drop.
- Consider using antimicrobial filters.
- Make sure the filter system is properly sealed to eliminate filter bypass.
- Inspect the air filter system regularly.
- Change filters at the proper intervals. To help with this, use reliable filter gauges.