CALPUFF Regulatory Status

CALPUFF has been adopted by the U.S. Environmental Protection Agency (U.S. EPA) in its  Guideline on Air Quality Models as the preferred model for assessing long range transport of pollutants and their impacts on Federal Class I areas and on a case-by-case basis for certain near-field applications involving complex meteorological conditions. CALPUFF is recommended by the U.S. EPA as a refined model for use in analyses for SO2 and particulate matter compliance assessments with ambient air quality standards and PSD increment consumption for (1) transport greater than 50km from a source, and (2) analyses involving a mixture of both long-range and short range source-receptor distances. The U.S. EPA Guideline on Air Quality Models also provides for the use of CALPUFF on a case-by-case basis for air quality estimates involving complex meteorological flow conditions, where steady-state straight-line transport assumptions are inappropriate. Download the November 9, 2005 Federal Register Notice for a complete description of the recently-promulgated revisions to the Guideline on Air Quality Models, including a description of the recommended regulatory uses of the CALPUFF modeling system. Also see the U.S. EPA SCRAM web site ( for more information on other EPA-recommended models.

The CALPUFF modeling system is recommended by the Federal Land Managers’ Air Quality Related Values Workgroup (FLAG) for assessing the effects of distant and multi-source plumes on visibility and pollutant wet/dry deposition fluxes. The CALPOST processor implements the FLAG recommended algorithms for assessing the change in plume extinction due to a modeled source or group of sources. CALPUFF postprocessors allow the calculation of pollutant deposition fluxes of nitrogen and sulfur as described by the FLAG guidance. Download the October 2010 FLAG Phase I Report Revised for more details.

The Interagency Workgroup on Air Quality Modeling (IWAQM) also recommends the use of CALPUFF. The Phase 2 Summary Report includes recommendations for conducting refined analyses with CALPUFF of PSD increment consumption, NAAQS impacts and Air Quality Related Value impacts in Class I areas. In addition, IWAQM discusses screening techniques for modeling worst-case impacts over long-range transport distances. Download the IWAQM Phase 2 Report (IWAQM, 1998) for more details.