Dispersion models are important to governmental agencies tasked with protecting and managing ambient air quality. These models are typically employed to determine whether existing or proposed new industrial facilities are or will be in compliance with the National Ambient Air Quality Standards (NAAQS) in the United States and other nations. Such models also serve in the design of effective control strategies to reduce emissions of harmful air pollutants. The Clean Air Act requires the U.S. Environmental Protection Agency to regulate airborne emissions of hazardous air pollutants (HAPs) from a specific list of industrial sources called "source categories." Each source category that emits radionuclides in significant quantities must meet the technology requirements to control them and is required to achieve specific regulatory limits. These standards are the National Emission Standards for Hazardous Air Pollutants for Radionuclides.
Air dispersion models also play an important role in emergency management organizations for emergency planning of accidental radiological, chemical, and/or biological releases. The models help estimate the consequences of accidental releases of hazardous or toxic materials. Accidental releases may result from fires, spills, or explosions that involve any hazardous materials that may become airborne. Through the use of worst case source terms and meteorological conditions, dispersion modeling provides a means of estimating the location of impact areas, air concentrations, and a means of forecasting changes in these hazards.