The levels of most air pollutants in indoor air exceed those observed outdoors, even in the nation's most polluted cities. Sources of indoor pollution are numerous and often poorly understood. Outdoor air entering buildings through natural or forced ventilation, generally contains only a small percentage of the toxic chemicals observed in indoor air. Many toxic chemicals are released to indoor environments by consumer products, including deodorizers, cleaning solutions, moth cakes, dry-cleaned clothes, paints, and candles. Even activities as seemingly harmless as cooking have been observed to lead to elevated levels of pollutants.
Building materials can also release toxic chemicals to the indoor environment.
Contributing materials include particleboard, carpet, adhesives, and more. Thus, it is important to consider building ventilation, HVAC systems, and energy conservation measures to understand and predict the overall quality of the indoor environment. For example, it was recently estimated that lost productivity due to illnesses generated by poor indoor air quality results in up to a 170 billion dollar annual loss to the U.S. economy. This figure does not reflect the magnitude of individual suffering that can occur due to such illnesses. Many experts now believe that poor indoor air quality plays a major role in this trend.