Where they are not, over-time individual vents may have been changed from original settings or there may have been changes in occupancy and space design. Additional return and supply air vents or other means of improving ventilation effectiveness may be needed. A re-balancing of the ventilation system to reflect current use and occupancy should be done by a professional balancing company. The capacity of the ventilation system to supply both total and fresh air for the occupancy and size of the space is often critical. Exhaust ventilation in restrooms and other areas should be provided and operating at all times of building occupancy.
Preventive maintenance is essential to the operation of all mechanical systems.
Elements within the ventilation system such as the condensate drip pans and heat exchanger coils need to be checked and cleaned periodically. Clogged drip pan drains can lead to microbiological growth and the release of allergens or pathogens into supply air. Filters should have a minimum efficiency of 25-30 percent. If windows are present and able to be opened, they should have screening and perhaps appropriate deflectors, to allow use without drafts. General cleanliness, in general and specific work areas, is an important component of perceived indoor air quality.