The "Guideline on Air Quality Models (Revised)" (hereinafter, the "Guideline"), as modified by supplement A (1987), sets forth air quality models and guidance for estimating ambient air concentrations due to sources of air pollutants. It is presently incorporated by reference into the prevention of significant deterioration regulations under the Clean Air Act. In this action, EPA added new models to the Guideline, improved existing models, incorporated supplement B as codified text and gave regulatory status to longstanding EPA policy regarding the use of air quality models for other regulatory programs.

• Requirements for Preparation, Adoption, and Submittal of Implementation Plans: Final Rule, Federal Register Notice (PDF)(69 pp, 4 MB, July 20, 1993, 58 FR 38816)