Indoor air quality is not a simple, easily defined concept like a 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. In addition, there are many other factors that affect comfort or perception of indoor air quality.
Studies indicate that persons in industrialized nations and mega cities spend 90% or more of their time indoors. The locations of highest concerns are those involving prolonged, continuing exposure – that is, home and workplace. Studies conducted by the U.S. Environmental Protection Agency (EPA) and others show that indoor environments sometimes can have levels of pollutants that are actually higher than levels found outside and also have consistently ranked indoor air pollution as important health problem.
Indoor air quality is a major concern to businesses, building managers, tenants, and employees because it can impact the health, comfort, well being, and productivity of building occupants.
“An EPA report to US congress estimates that poor indoor air may cost the nation tens of billions of dollars each year in lost productivity and medical care and an improved indoor air quality can result in higher productivity and fewer lost work days.”
Management of pollutants sources, both inside and outside the building
Pollutants can be generated by outdoor sources or indoor sources, including industrial pollution, construction, traffic, 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 occupants’ exposure to pollutants from these sources. Some key pollutant categories include:
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, inadequate humidity control, condensation, or may be brought into the building by occupants, infiltration, or ventilation air. Allergic responses to indoor biological pollutant exposures cause symptoms in allergic individuals and a key role in triggering asthma episodes for millions of asthma sufferers.
The transmission of airborne infectious diseases is increased where there is poor indoor air quality. Evidence is increasing that inadequate or inappropriately designed ventilation systems in health care settings or other crowded conditions can increase the risk of exposure.
Chemical pollutants: Sources of chemical pollutants include industrial and vehicular emissions, tobacco smoke, volatile organic compounds(VOCs) from products used inside the building (e.g., office equipment; furniture, wall and floor coverings; and cleaning and consumer products) accidental spill of chemicals, and gasses such as carbon monoxide and nitrogen dioxide, which are products of combustion. A study by EPA found indoor levels of VOCs ten times higher than outdoors – even in locations with significant outdoor air pollution sources, such as petrochemical plants.
Particles: Particles are solid or liquid substances which are light enough to be suspended in the air, the largest of which may be visible in sunbeams streaming into a room. However, smaller particles that you cannot see are likely to be more harmful to health. Particles of dust, dirt, or other substances may be drawn into the building from outside and can also be produced by activities that occur in buildings like sanding wood or drywalls, printing, copying, operating equipment, and smoking.
People can react differently when exposed to the same contaminants at similar concentrations. For example, some people can develop severe allergic reactions to biological contaminants to which other people will not react. Similarly, exposure to very low levels of chemicals may be irritating to some people but not others. For people with asthma and other pre-existing conditions, exposure to irritants like environmental tobacco smoke or certain gasses or particles from various indoor sources may cause more severe reactions than the same exposure would in others.
