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AP-42 Emissions Factors (WebFIRE)

Published by U.S. EPA Office of Air and Radiation (OAR) - Office of Air Quality Planning and Standards (OAQPS) | U.S. Environmental Protection Agency | Metadata Last Checked: July 31, 2025 | Last Modified: 2014-01-01
Emissions factors have long been the fundamental tool in developing national, regional, state, and local emissions inventories for air quality management decisions and in developing emissions control strategies. More recently, emissions factors have been applied in determining site-specific applicability and emissions limitations in operating permits by federal, state, local, and tribal agencies, consultants, and industry. AP-42 is a compendium of EPA recommended emissions factors.

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