Indoor air quality is not a simple, easily defined concept like a wobbly desk or a leaky faucet. It is a constantly changing interaction of complex factors that affect the types, levels, and importance of pollutants in indoor environments. These factors include: sources of pollutants or odors; design, maintenance and operation of building ventilation systems; moisture and humidity; and occupant perceptions and susceptibilities. These and many other factors affect comfort or perception of indoor air quality.
Pollutants can be generated by outdoor or indoor sources, including building maintenance activities, pest control, housekeeping, renovation or remodeling, new furnishings or finishes, and building occupant activities. One important goal of an indoor air quality program is to minimize people’s exposure to pollutants from these sources. Some of the key pollutant categories include biological contaminants, chemical pollutants, and particles.
Biological contaminants
Excessive concentrations of bacteria, viruses, fungi (including molds), dust mite allergen, animal dander, and pollen may result from inadequate maintenance and housekeeping, water spills, and inadequate humidity control leading to moisture condensation on surfaces. Dust mites, like the one in Figure 1, can cause reactions in individuals prone to allergic reactions. These organisms are introduced into the building by occupants, infiltration, or ventilation air. Allergic responses to indoor biological pollutant exposures cause symptoms in allergic individuals and also play a key role in triggering asthma episodes for an estimated 15 million Americans.
Chemical pollutants
Sources of chemical pollutants include tobacco smoke, emissions from products used in constructing and furnishing a
building (e.g., office equipment; furniture, wall and floor coverings; and cleaning and consumer products), accidental spill of chemicals, and gaseous products of combustion such as carbon monoxide and nitrogen dioxide. Cleaning products, like those seen in Figure 2, can become pollutants if spilled or not stored properly.
