EPA prepares the National Emissions Inventory (NEI), a comprehensive and detailed estimate of air emissions of both Criteria and Hazardous air pollutants from all air emissions sources. The NEI is prepared every three years by the USEPA based primarily upon emission estimates and emission model inputs provided by State, Local, and Tribal air agencies for sources in their jurisdictions, and supplemented by data developed by the USEPA.
See: 2011 National Emissions Inventory (NEI) Documentation
2014 National Emissions Inventory (NEI) Information
EPA also develops and provides information about emission factors. An emissions factor is a tool used to estimate air pollutant emissions from a normally-operating process or activity (e.g., fuel combustion, chemical production). An emissions factor relates the quantity of pollutants released to the atmosphere from a process to a specific activity associated with generating those emissions.
To learn more about Emissions Factors, See: Clearinghouse for Inventories and Emission Factors
In addition, WebFIRE is EPA’s online emissions factor repository, retrieval, and development tool. The WebFIRE database contains EPA’s recommended emissions factors for criteria and hazardous air pollutants (HAP) for industrial and non industrial processes.