The Emissions Modeling Clearinghouse (EMCH) supports and promotes emissions modeling activities both internal and external to the EPA. Through this site, the EPA distributes and documents emissions datasets that are formatted for use in emissions models, which are used for emissions preparation for air quality modeling. The inventory data on this site are dervied from previous and current versions of the National Emission Inventory (NEI). This site also distributes the EPA's latest versions of ancillary datasets used to support the temporal, spatial, speciation, and future-year projection of these emissions.