An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Air Emissions Inventories

2008 NEI Technical Support Document

The primary purpose of this technical support document is to explain the sources of information included in the inventory. This includes showing which sources of data are used for each sector, and then providing more information about the EPA-created components of the data.

The Appendices shows the percentage of emissions from different data sources in 2008 NEI by pollutant and EIS sector. The data sources are grouped from the full suite of datasets used to compile the 2008 NEI.

You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.