The relative importance of any single source depends on how much of a given pollutant it emits, how hazardous those emissions are, occupant proximity to the emission source, and the ability of the ventilation system (i.e., general or local) to remove the contaminant. In some cases, factors such as the age and maintenance history of the source are significant.
Sources of indoor air pollution may include:
Building Site or Location:
The location of a building can have implications for indoor pollutants. Highways or busy thoroughfares may be sources of particulates and other pollutants in nearby buildings. Buildings sited on land where there was prior industrial use or where there is a high water table may result in leaching of water or chemical pollutants into the building.
Design and construction flaws may contribute to indoor air pollution. Poor foundations, roofs, facades, and window and door openings may allow pollutant or water intrusion. Outside air intakes placed near sources where pollutants are drawn back into the building (e.g., idling vehicles, products of combustion, waste containers, etc.) or where building exhaust reenters into the building can be a constant source of pollutants. Buildings with multiple tenants may need an evaluation to ensure emissions from one tenant do not adversely affect another tenant.
Building Systems Design and Maintenance:
When the HVAC system is not functioning properly for any reason, the building is often placed under negative pressure. In such cases, there may be infiltration of outdoor pollutants such as particulates, vehicle exhaust, humid air, parking garage contaminants, etc. Also, when spaces are redesigned or renovated, the HVAC system may not be updated to accommodate the changes. For example, one floor of a building that housed computer services may be renovated for offices. The HVAC system would need to be modified for office employee occupancy (i.e., modifying temperature, relative humidity, and air flow).
When painting and other renovations are being conducted, dust or other by-products of the construction materials are sources of pollutants that may circulate through a building. Isolation by barriers and increased ventilation to dilute and remove the contaminants are recommended.
Local Exhaust Ventilation:
Kitchens, laboratories, maintenance shops, parking garages, beauty and nail salons, toilet rooms, trash rooms, soiled laundry rooms, locker rooms, copy rooms and other specialized areas may be a source of pollutants when they lack adequate local exhaust ventilation.
Disturbing thermal insulation or sprayed-on acoustical material, or the presence of wet or damp structural surfaces (e.g., walls, ceilings) or non-structural surfaces (e.g., carpets, shades), may contribute to indoor air pollution.
Cabinetry or furniture made of certain pressed-wood products may release pollutants into the indoor air.
Workers in areas in which pesticides, cleaning products, or personal-care products are being applied may be exposed to pollutants. Allowing cleaned carpets to dry without active ventilation may promote microbial growth.
Building occupants may be the source of indoor air pollutants; such pollutants include perfumes or colognes.