Quick removal of concentrated air contaminants and building pressurization are two ways that exhaust systems affect IAQ. Special use areas such as science labs, vocational/technical shops, cafeterias, and indoor pools already have well established regulatory codes regarding ventilation with outdoor air and negative pressure requirements with respect to adjacent spaces. Less well recognized areas in schools where special exhaust ventilation is desirable are janitor closets, copy/work rooms and arts/crafts preparation areas where off-gasing from significant quantities of materials or products may occur. These areas should be maintained under negative pressure relative to adjacent spaces.

• Provide exhaust ventilation for janitor’s closets.

If housekeeping and maintenance supplies are properly stored in janitor closets, only enough air need be exhausted to place the closet under negative pressure relative to surrounding rooms. As long as air does not easily leak into or from the closet through openings such as plenums or utility chases, 10 CFM of air exhausted from the room will typically make it negative, and prevent the buildup of air pollutants.

• Provide exhaust ventilation for copy/work rooms.In addition to the code-required amount of outdoor air being supplied to this room for general ventilation, it is desirable to determine what types of equipment and activities the school plans for this room, and to supply special exhaust ventilation for concentrated pollutant sources. Two examples of sources are copy machines and work areas for adhesives. Most copier manufacturers can provide an optional vent kit, which is usually a simple plastic fitting, that allows a piece of 3″ or 4″ diameter flexible duct to be connected between the copier and an exhaust fan. This captures much of the heat, particles, ozone, and other pollutants and exhausts them outdoors before they can spread throughout the workroom. A small exhaust hood over a work surface, similar to a fume hood in a science lab, would also be helpful to reduce exposure when adhesives, sprays, paints, and solvents are being used in the workroom.
• Provide exhaust ventilation for arts and crafts preparation areas where off-gassing from significant quantities of materials or products may occur.
  
• Consider specifying a differential pressure monitor to monitor building pressurization.IAQ problems are often traced to improper pressurization, which causes unexpected airflow between indoors and outdoors, and between areas within the school. To reduce introduction of unconditioned moist air and pollutants from outdoors, the building should be designed to operate between zero and 0.03 in. w.g. (0 to 7 Pa) positive, relative to outdoors.
• Do not operate exhaust systems when the HVAC system is turned off to avoid bringing in unconditioned moist air that may condense on cooler indoor surfaces.