AP-42: Compilation of Air Emissions Factors from Stationary Sources

Alerts

5/28/25 - EPA has finalized AP-42 Chapter 11, Section 7 – Ceramic Clay Manufacturing. The finalized factors, the comment received, the response to the comment, and the final AP-42 section can be found on the Final Revisions to AP-42 Chapter 11, Section 7 – Ceramic Clay Manufacturing page. 

3/13/25 - EPA has extended the public comment period deadline to August 18, 2025 for AP-42 Chapter 9 Section 4 - Livestock and Poultry Feed Operations and included the associated emission model reports for animal feeding operations and VOC emissions from animal sectors.  Comments should be sent to the NAEMS Group (NAEMS@epa.gov).

11/19/2024 - EPA has drafted a new AP-42 Chapter 9 Section 4 - Livestock and Poultry Feed Operations and included the associated emission model reports for animal feeding operations and VOC emissions from animal sectors for review. This section and these models can be found on the Draft AP-42 Chapter 9, Section 4 - Livestock and Poultry Feed Operations and Air Emissions Estimating Methodologies for Animal Feeding Operations page. The EPA is offering 90-day public review period that will end on February 17, 2025. Comments should be sent to the NAEMS Group (NAEMS@epa.gov).

Compilation of Air Pollutant Emissions Factors from Stationary Sources (AP-42)

AP-42, Compilation of Air Pollutant Emissions Factors from Stationary Sources, has been published since 1972 as the primary compilation of EPA's emissions factor information. It contains emissions factors and process information for more than 200 air pollution source categories. A source category is a specific industry sector or group of similar emitting sources. The emissions factors have been developed and compiled from source test data, material balance studies, and engineering estimates. The latest emissions factors are available below on this website. Use the AP-42 Chapter webpage links below to access the document by chapter. Emission factors are being updated as data are received and evaluated. 

AP-42, Compilation of Air Pollutant Emissions Factors from Stationary Sources 

ChapterTitle
 Table of Contents AP-42 Table of Contents (pdf) (245.41 KB)
Introduction  AP-42 Introduction (pdf) (288.31 KB)
Chapter 1External Combustion Sources
Chapter 2Solid Waste Disposal
Chapter 3Stationary Internal Combustion Sources
Chapter 4Evaporation Loss Sources
Chapter 5Petroleum Industry
Chapter 6Organic Chemical Process Industry
Chapter 7Liquid Storage Tanks
Chapter 8Inorganic Chemical Industry
Chapter 9Food and Agricultural Industries
Chapter 10Wood Products Industry
Chapter 11Mineral Products Industry
Chapter 12Metallurgical Industry
Chapter 13Miscellaneous Sources
Chapter 14Greenhouse Gas Biogenic Sources
Chapter 15Ordnance Detonation
Appendix A Miscellaneous Data and Conversion Factors (pdf) (88.1 KB)  -- September 1985
Appendix B.1 Particle Size Distribution Data and Sized Emission Factors for Selected Sources (pdf) (1.78 MB) -- October 1986
Appendix B.2 Generalized Particle Size Distributions (pdf) (132.81 KB)  -- September 1996
Appendix C.1 Procedures for Sampling Surface/Bulk Dust Loading (pdf) (65.05 KB)  -- July 1993
Appendix C.2 Procedures for Laboratory Analysis of Surface/Bulk Dust Loading Samples (pdf) (43.39 KB)  -- July 1993
Chapter References AP-42 Chapter References 

AP-42 Draft Emissions Factors for Review

Chapter & SectionDescriptionComments Requested by:
9.4Livestock and Poultry Feed Operations and Air Emissions Estimating Methodologies for Animal Feeding Operations08/18/2025

Documentation Supporting Draft and New Emissions Factors

Other AP-42 Information

AP-42 FAQ

Previous Versions , Supplements and Updates 

Emission Factor Improvements Rulemaking 

Air Emissions Factors and Quantification

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Last updated on February 9, 2026