Atmospheric dispersion models are computer programs that use mathematical algorithms to simulate how pollutants in the ambient atmosphere disperse and, in some cases, how they react in the atmosphere. The dispersion models are used to estimate or to predict the downwind concentration of air pollutants emitted from sources such as industrial plants and and vehicular traffic. Such models are important to governmental agencies tasked with protecting and managing the ambient air quality. The models are typically used to determine whether existing or proposed new industrial facilites are or will be in compliance with national ambient air quality standards. The models may also be used assist in the design of effective control strategies to reduce emissions of harmful air pollutants.