Regulatory Dispersion Model AERMOD Updated

An update to the AERMOD dispersion model was released by EPA on October 23, 2009. This new release, version 09292, contains a number of modifications and enhancements to the previous version (07026). A detailed list of changes can be found in the latest Model Change Bulletin (MCB) available for download from Trinity's BREEZE Website at The list of enhancements includes the following:

  • Additional options to vary emissions by hour-of-day and day-of-week
  • Improved efficiency of allocating array storage
  • Option to specify hourly varying release height and initial dispersion coefficients for volume and area sources
  • Increased maximum filename length to 200 characters
  • Allowance to use optional methods for particulate and gaseous emissions from open pit sources

BREEZE AERMOD, from Trinity Consultants, was updated to incorporate EPAs changes into all versions of the model. Users with current software maintenance were provided with the update at no charge. Other users can obtain updated products by contacting