Support Center for Regulatory Atmospheric Modeling (SCRAM)

The Guideline on Air Quality Models provides the requirements and recommendations for regulatory air quality modeling
Photochemical and Dispersion models are critical components of regulatory compliance demonstrations
Air quality modeling projects the impacts of air emissions to ensure regulatory compliance
Air quality modeling supports regulatory programs required by the Clean Air Act

This website provides access to air quality models and other mathematical simulation techniques used in assessing control strategies and source impacts.

Air Quality Models

Dispersion Modeling
Photochemical Modeling
Receptor Modeling

Modeling Applications and Tools

Photochemical Modeling Applications
Photochemical Modeling Tools
Dispersion Modeling Applications
Multipollutant Modeling Applications

Modeling Guidance and Support

Permit Modeling Guidance
State Implementation Plan Attainment Demonstration Guidance
Applicable Guidance for Air Toxics Modeling
Model Clearinghouse
State and EPA Regional Modeling Contacts

Meteorological Data and Processors

Observational Meteorological Data
Meteorological Grid Models
Meteorological Guidance

Training and Resources

Conferences and Workshops
Reports and Journal Articles
Resources from Selected Organizations

Announcements

12/10/2025 - The presentation from the 2024 Revisions to Appendix W / AERMOD Final Rule Webinar is now available.

12/04/2024 - An AERMOD 64-bit Executable Refresh Memorandum is now available.

11/20/2024 - The final rule revising the Guideline on Air Quality Models (Appendix W to 40 CFR Part 51) was signed by the EPA Administrator on Wednesday, November 20, 2024.

11/20/2024 - An updated version of the AERMOD Modeling System (dated 24142), including new versions of AERMOD, AERMET, and AERMAP, and updated versions of AERSUFACE (v24142), AERPLOT (v24142), and MMIF (v4.1.1) are now available.

11/20/2024 - The final Guidance on Developing Background Concentrations for Use in Modeling Demonstrations is now available.

09/20/2024 - A Model Clearinghouse Concurrence Memorandum to Region 2 regarding the use of a site-specific alternative approach to demonstrate modeled attainment of the 2010 SO2 NAAQS at the Alcoa West Aluminum Smelter in Massena, New York has been added to the MCHISRS database.

08/27/2024 - A Model Clearinghouse Concurrence Memorandum to Region 2 regarding the use of AERCOARE-AERMOD as an alternative model for an Outer Continental Shelf permitting effort (Atlantic Shores P3Co Project) has been added to the MCHISRS database.

08/05/2024 - The final presentations from the 2024 Regional, State, and Local (RSL) Dispersion Modelers' Workshop are now available.

07/24/2024 - A Model Clearinghouse Concurrence Memorandum to Region 6 regarding the use of AERMOD-HBP as an alternative model for a 1-hour SO2 attainment demonstration SIP effort (Rusk-Panola Nonattainment Area) has been added to the MCHISRS database.

06/14/2024 - A Model Clearinghouse Concurrence Memorandum to Region 1 regarding the use of AERCOARE-AERMOD as an alternative model for an Outer Continental Shelf permitting effort (Vineyard Wind NE) has been added to the MCHISRS database.

04/30/2024 - Supplement to the Guidance on Significant Impact Levels for Ozone and Fine Particles in the Prevention of Significant Deterioration Permitting Program

04/30/2024 - Effective Permitting Tools for Fine Particulate Matter under the Prevention of Significant Deterioration Permitting Program Fact Sheet

See Historical Announcements

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