To ensure that Virginians enjoy clean air, DEQ monitors air quality at dozens of locations throughout the state. In partnership with state, local and federal agencies, DEQ monitors criteria pollutants, toxic air pollutants, and other parameters, using methods and procedures approved by the U.S. Environmental Protection Agency.

Criteria pollutants are carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone, lead and particulate matter, which are the six contaminants that cause acid rain, smog and other health hazards.

DEQ collects data in order to classify air quality, document compliance with national ambient air quality standards and provide real-time reporting of the air quality index.

Federal regulations establish requirements for the number and location of monitors, although states may expand monitoring networks to meet their needs. Each year, DEQ submits its network plan to EPA for approval, which provides detailed information about monitoring sites and any planned changes.

Most sites in Virginia are concentrated in populated areas, with locations determined by population, emissions sources, permitting needs, modeling results and site accessibility. Monitoring sites are also found in rural areas, where analyzers measure background, pollution that originated from other locations and source-specific pollution.