See our Air Pollution Data page for further information. An emission factor is a representative value that attempts to relate the quantity of a pollutant released into the atmosphere to an activity associated with the release of that pollutant. Such factors may be used in equations to estimate emissions from a process where more specific data is not available. Our Introduction to Emission Factors page contains a more detailed discussion. One of the first activities for developing an air quality control strategy for these areas is to prepare an inventory of the emissions of interest.
Emission inventories can serve many purposes.
They are used in ambient dispersion modeling and analysis, control strategy development, and in screening sources for compliance investigations. Together with ambient monitoring data, inventory emission estimates have been used as a direct indicator of annual changes in air quality. The inventory also serves as the basis for the annual National Air Pollutant Emission Trends report. The estimates are made for over 450 individual source categories that include all major sources of anthropogenic emissions for the years 1900 through 1984. The National Air Pollutant Emission Trends report presents the latest estimates of national and regional emissions for criteria air pollutants .