• Unclassified: a pollutant is designated unclassified if the data are incompete and do not support a designation of attainment or nonattainment.

• Attainment: a pollutant is designated attainment if the state standard for that pollutant was not violated at any site in the area during a three-year period.

• Nonattainment: a pollutant is designated nonattainment if there was at least one violation of a State standard for that pollutant in the area.

• Nonattainment / Transitional: is a subcategory of the nonattainment designation. An area is designated nonattainment / transitional to signify that the area is close to attaining the standard for that pollutant.

The size of the designated area may vary depending on the pollutant, the location of contributing emission sources, the meteorology, and the topographic features. The Board may designate areas smaller than an air basin or county, if the Board finds that a smaller area has distinctly different air quality.

• Air Basin: is the area designated for ozone, nitrogen dioxide, PM10, sulfates, and visibility reducing particles.

• County: (or the portion of a county located within an air basin) is the area designated for carbon monoxide, sulfur dioxide, lead, and hydrogen sulfide.

• See section 70300 through 70306 and Appendices 1 through 4 of the California Code of Regulations, Title 17)