Best available control technology (BACT) is a standard used in air pollution control in the prevention of significant deterioration (PSD) of air quality in the United States. Under the Clean Air Act, a major stationary new source of air pollution, such as an industrial plant, is required to have a permit that sets emission limitations for the facility. As part of the permit, limitations are based on levels achievable by the use of BACT for each pollutant.

To prevent risk to human health and public welfare, each region in the country is placed in one of three PSD areas in compliance with National Ambient Air Quality Standards (NAAQS). Class I areas include national parks and wilderness areas, where very little deterioration of air quality is allowed. Class II areas allow moderate increases in ambient concentrations. Those classified as Class III permit industrial...