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  2. General Conformity

Modeling Clarification Memorandum for Secondary Pollutants and Nitrogen Dioxide

EPA has clarified that air quality “modeling,” referring to the use of air quality modeling techniques, databases, or computer models to assess impacts to the National Ambient Air Quality Standards, is sufficient and appropriate for a demonstration of General Conformity when following the EPA 2017 Guideline on Air Quality Models (the Guideline). Federal agencies may rely upon the recommendations in the Guideline for demonstrating conformity of secondarily formed criteria pollutants when their actions are proposed to occur within nitrogen dioxide (NO2), ozone (O3), or fine particulate matter (PM2.5) nonattainment or maintenance areas.

Historically, EPA has recommended that federal agencies not use air quality modeling to demonstrate General Conformity for these areas because the science and technology of the models, and their capabilities, were not sufficient to handle the complexities of photochemical reactions in the atmosphere from a relatively small source. Recent advances in modeling, and EPA’s innovative, alternative modeling techniques, can now support the use of air quality modeling to demonstrate General Conformity of these pollutants using the recommendations of the Guideline. 

Read the Modeling Clarification Memorandum below. 

  • Use of Modeling Techniques to Demonstrate General Conformity for Ozone, Fine Particulate Matter and Nitrogen Dioxide (pdf) (2.81 MB)

General Conformity

  • What is General Conformity?
  • Basic Information About the Rule
  • Regulatory Actions
  • Training Modules I - IV
    • Module I: The Basics
    • Module II: Key Concepts
    • Module III: The Details
    • Module IV: State, Local, Tribal
    • Appendix A Sample Emissions Calculations
    • Appendix B 2010 Revisions to the Regulations
    • Glossary for Training Modules
Contact Us about General Conformity
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Last updated on September 10, 2024
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