Air toxics computational fluid dynamics (CFD) is an emerging scientific method for calculating human exposure to toxic air pollutants. The U.S. Environmental Protection Agency (EPA) defines toxic air pollutants, also known as hazardous air pollutants, as those pollutants that are known or suspected to cause cancer or other serious health effects, such as reproductive effects, birth defects, or adverse environmental effects. Most air toxics originate from human-made sources, including mobile sources (for example, cars, trucks, and buses) and stationary sources (for example, factories, refineries, and power plants), as well as indoor sources (for example, some building materials and cleaning solvents). Some air toxics are also released from natural sources, such as from volcanic eruptions and forest fires. People are exposed to toxic air pollutants in many ways that can pose health risks, including directly by breathing contaminated air or indirectly by consuming or contacting materials that have been exposed to contaminated air. Accurate estimates of exposures can be supported through a measurement of the contaminated air concentration being breathed or surrounding the material. However, measurements are expensive and very few in number. As a result, measurements are not possible everywhere that they are needed.