State Area Designations Definitions
This page last reviewed January 27, 2014
For State Area Designations, there are three basic designation categories, and one sub-category. More detailed information regarding these categories can be found in the Regulatory Reference below.
- Nonattainment: is the category for an area has one or more violations within the last three years.
- Nonattainment-Transitional: is a subcategory of nonattainment. For ozone, there must be three or fewer exceedances in the last year.
- Attainment: is the category given to an area with no violations in the last three years.
- Unclassified: is the category given to an area with insufficient data.
Exceedance versus Violation
- Exceedance: is a concentration higher than the State standard. Some exceedances may be excluded if determined to be caused by an exceptional event, such as a wildfire or dust storm. Not all exceedances are violations.
- Violation: is a concentration higher than the State standard which is not determined to be caused by an exceptional event.
Geographic Extent of DesignationsThe 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. Further information, including maps, can be found on the California Air Basins webpage.
- 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 3 of the California Code of Regulations, Title 17