The environmental concern for air pollution has been largely focussed on questions of outdoor air contamination* Recently, however, attention has begun to shift to concerns about the quality of air within buildings. In the United States today, people spend only 10-15* of their time outdoors; the rest is spent at home, at work, or traveling in between. Yet existing air quality regulations are based solely on outdoor conditions, specifically on large-scale, highly visible, outdoor air-pollution sources, such as industrial effluents and vehicle exhaust. Buildings were assumed to shelter occupants from outdoor pollutants, and little thought was given to pollutants generated or trapped indoors. Recent studies have shown that concentrations of certain pollutants inside houses exceed standards set for outdoor concentrations. Because health effects are often correlated with exposure over time, it is now clear that air quality indoors requires far more attention than it has yet received. As an emerging health problem, contamination of indoor air has been linked with a wide variety of building materials and consumer products, as well as strategies that reduce the amount of infiltrating air as a means of promoting energy conservation...