This polygon layer contains a spatial representation of geographic areas that are designated as Air Quality Maintenance Areas and Nonattainment Areas for the criteria pollutant CARBON MONOXIDE. A criteria pollutant means any of the six pollutants set out by the Clean Air Act (sulfur oxides, particulate matter, ozone, carbon monoxide, nitrogen dioxide, and lead) for which the EPA has promulgated standards in 40 CFR 50.4 through 50.12 (July, 1993).