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Photochemical Modeling Tools


The Air Quality Modeling Group has developed the Modeled Attainment Test Software (MATS). MATS is a PC-based software tool that can perform the modeled attainment tests for particulate matter (PM2.5) and ozone (O3), and calculate changes in visibility at Class I areas as part of the uniform rate of progress analysis for regional haze. Detailed information on the recommended attainment tests can be found in U.S. EPA's modeling guidance, Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of the Air Quality Goals for Ozone, PM2.5, and Regional Haze."


  • MATS version 2.5.1: Version 2.5.1 includes an update to the 24-hour PM2.5 attainment test as outlined in the following guidance memo: Update to the 24 Hour PM2.5 NAAQS Modeled Attainment Test
    Additional changes are documented here: version 2.5.1 change log This version performs the ozone, annual average PM2.5, 24-hour PM2.5, and visibility tests outlined in the modeling guidance. Note that spatial fields for the 24-hr PM2.5 test are not implemented in this version.

    There are updates to the ambient datasets in this installer package (see change log). Updates to ambient datasets will be included in future releases.

    If a previous version of MATS is installed, please uninstall the old version (using Windows "add or remove programs") before installing the new version.

    • MATS 2.5.1 installer package - The installer package is large (~200Mb) due to the inclusion of several large example model and ambient datasets.

    • MATS 2.5.1 executable - The executable (~7Mb) will only work if the installer package is installed first. We are providing the executable as a separate download because there may be periodic updates to the executable that don't require downloading and installing the entire installer package.

    • MATS 2.5.1 User's Manual - A PDF version of the user's manual is also included in the MATS installer package. Additionally, the user's manual is built into the help section of the MATS graphical user interface.


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