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Air Quality Planning and Standards

Air Quality Modeling

The basic mission of the Office of Air Quality Planning and Standards is to preserve and improve the quality of our nation's air.  One facet of accomplishing this goal requires that new and existing air pollution sources be modeled for compliance with the National Ambient Air Quality Standards (NAAQS).  The following are some of the topics and areas associated with air quality modeling:

Support Center For Regulatory Air Models (SCRAM)

The Support Center For Regulatory Air Models (SCRAM) site provides information about mathematical models used to predict the dispersion of air pollution. The site includes computer codes, meteorological input data, documentation and guidance on usage. Its primary purpose is to provide air pollution control agencies with air quality models and related information that support selected requirements of the Clean Air Act.

EPA Regional Modeling Center

The EPA Regional Modeling Center  provides information and data associated with regional applications performed by the OAQPS/EMAD to support EPA policy development and regulatory actions.  The site includes a description of modeling projects, tabular and graphical  summaries of the emissions scenarios, simulated  model results, and access  to emissions and meteorological inputs and predictions.

Model Clearinghouse

The Modeling Clearinghouse is a single EPA focal point for reviewing the use of modeling techniques in specific regulatory applications.  In that capacity the Clearinghouse reviews specific actions which involved interpretations of modeling guidance, e.g., Regional Office acceptance of non guideline models and data bases.   The public has access to Clearinghouse memoranda and reports via the SCRAM website.

Air Toxics Modeling

Dispersion models are used to support a variety of air toxics regulations.  Several models, user's guides and guidance documents are available for these purposes from the Support Center for Regulatory Air Models (SCRAM) website.  One of the most commonly used dispersion models is the Industrial Source Complex (ISC3) model.  This model is accompanied by a three volume user's guide.  For screening level analyses, the TSCREEN  model is useful.  This user friendly model is accompanied by a user's guide and a document "Workbook of Screening Techniques for Assessing Impacts of Toxic Air Pollutants (Revised)" which contains useful information on air toxics modeling concepts.  In addition, EPA has developed "Guidance on the Application of Refined Dispersion Models for Hazardous/Toxic Air Releases" which provides guidance on the use of dense gas models.

Air Quality Modeling Group

The air quality modeling group provides leadership and direction on the full range of atmospheric dispersion models and other mathematical simulation techniques used in assessing source impacts and control strategies.  The Group serves as the focal point on modeling techniques for other EPA headquarters staff, Regional Offices, and State and local agencies.  It coordinates with the Office of Research and Development on the development of new models and techniques, as well as wider issues of atmospheric research.  Finally, the Group conducts modeling analyses to support policy/regulatory decisions in the Office of Air Quality Planning and Standards. 

Clearinghouse for Inventories and Emission Factors (CHIEF)

The Clearinghouse for Inventories and Emission Factors (CHIEF) provides access to tools for estimating emissions of air pollutants and preparing air emission inventories. CHIEF serves as EPA's central clearinghouse for the latest information on air emission inventories and emission factors. Emission estimation data bases, newsletters, announcements, and guidance on performing inventories are included in CHIEF.

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