The study of aerosols in indoor air and the assessment of human exposure to aerosols are relatively recent activities. The terms indoor air and exposure assessment refer primarily to nonindustrial settings, such as homes, offices, and public-access buildings (e.g., museums, airport terminals, retail stores). Although many occupational settings are 'indoors', the aerosol concentrations and constituents, airflow regimes, and turbulence levels pose related, but different, aerosol measurement constraints. Until recently, it was commonly believed that the quality of indoor air was superior to that of the outdoor (ambient) air nearby. Several factors have influenced the apparent deterioration of indoor air quality: life-styles have changed; building construction techniques have changed; and people have become more concerned about environmental tobacco smoke (ETS).

Caption title. Chapter from "Aerosol Measurement: Principles, Techniques, and Applications" edited by Klaus Willeke and Paul A. Baron. Includes bibliographical references (p.683-689).