The U.S. EPA has proposed a number of revisions to the Guideline on Air Quality Models, published as Appendix W to 40 CFR Part 51 (Appendix W) in 2005, many of which are discussed in depth here. The proposed revisions include a large amount of new material as well as the reorganization or removal of outdated or obsolete information, and the U.S. EPA is planning to have the final rulemaking and promulgation of the revised Guideline in Summer 2016.

In response to one of the proposed revisions – the replacement of CALINE3 with AERMOD – BREEZE Software conducted a comparison study to evaluate the proposed replacement. By using results from a field study conducted in downtown Los Angeles in 2008, the model performance of AERMOD, CALINE4, and RLINE (a research model specifically for roadway sources developed by U. S. EPA’s Office of Research and Development) were evaluated and compared. The findings from the study support the proposed replacement of CALINE3 with AERMOD when onsite meteorological data is used as input for AERMOD. Read the full comparison study.

Last month, BREEZE Software presented the findings from this study at the AWMA 6th Specialty Conference in Chapel Hill, North Carolina. This month, BREEZE Software will be discussing the findings at the 17th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes in Budapest, Hungary.


Over 4,000 environmental professionals in more than 90 countries use BREEZE software to assess the impacts of air emissions, fires, and explosion. In addition to developing sophisticated modeling software programs, BREEZE also offers quality-assured model-ready meteorological and terrain data, professional training, high-speed modeling solutions, and specialized consulting services.

For more information on BREEZE Software, visit or email Subscribe to BREEZE News to stay on top of the modeling tips, latest software updates and events.