CRACMM Mechanism After One Year

The Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM) After One Year

CRACMM is a chemical mechanism designed to treat all reactive organic carbon emissions to enable the best predictions of ozone, particulate matter, and hazardous air pollutants.

Version 1 was distributed in CMAQv5.4 released in October of last year. Since the release, several manuscripts documenting and applying CRACMM to understand the role of different emissions in pollutant endpoints have been published and are now highlighted on the EPA website.

In addition, the CMAQ team has set a timeline for releases through 2026 when CRACMM will become the ORD default mechanism. To learn more about CRACMM and the future of chemical mechanisms in CMAQ, see and the updated fact sheet.