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Air Emissions Factors and Quantification

  • What is an emission factor?

    An emissions factor is a representative value that attempts to relate the quantity of a pollutant emitted with an industrial activity.

Emissions factors are tools for building emissions inventories, guiding air quality management decisions and developing emissions control strategies.  

Alerts

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).

10/18/2024 - EPA has drafted new/revised emission factors for AP-42 Chapter 11, Section 7 – Ceramic Products Manufacturing. These factors can be found on the Draft Revisions to AP-42 Chapter 11, Section 7 – Ceramic Products Manufacturing page. Comments will be accepted through December 17, 2024.

10/10/2024 - EPA has finalized AP-42 Chapter 7, Section 1 – Organic Liquid Storage Tanks. The response to comments, a summary of changes made, and the final AP-42 section can be found on the  Final Revisions to AP-42 Chapter 7, Section 1 – Organic Liquid Storage Tanks page.

10/9/2024 -  EPA released TANKS 5.1 - an updated/final version of the TANKS 5.0 Beta application. This updated version includes improved and additional features, as well as bug fixes. To receive notifications related to application updates, sign up for the CHIEF Listserv by sending an e-mail to join-chief@lists.epa.gov. 

Air Emissions Factors / AP-42

  •  Basic Information About Air Emissions Factors and Quantification
  •  AP-42 Compilation of Air Pollutant Emissions Factors

Web Factor and Information Retrieval System (WebFIRE)

  •  WebFIRE

Emissions Estimation Tools

  • Spreadsheets and Methodology Documents
  • Software:  TANKS, SPECIATE, LandGEM, WATER9

See also Clearinghouse for Inventories and Emissions Factors (CHIEF)

Contact Us to ask a question, provide feedback, or report a problem.
Last updated on May 21, 2025
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