Dispersion modeling uses mathematical formulations to characterize the atmospheric processes that disperse a pollutant emitted by a source. This type of modeling is most often associated with the air permitting process and used to determine compliance with National Ambient Air Quality Standards (NAAQS) and other regulatory requirements.

Permit applicants must consult the Air Assessments staff and the appropriate DEQ regional office to ensure that modeling is performed correctly and is consistent with the information contained in the air permit application.

Photochemical models are typically used in regulatory or policy assessments to simulate the impacts from all sources by estimating pollutant concentrations and deposition. These models are often used for regulatory analysis and NAAQS attainment demonstrations (e.g., ozone and PM2.5) by assessing the effectiveness of pollution control strategies.

This modeling is performed by DEQ as well as through regional planning organizations. The modeling process follows EPA guidelines for regulatory application so that the modeling results can be used in the agency’s regulatory and policy planning.