California Air Resources Board

The Clean Air Act, which is federal law, describes the procedures that regulatory agencies must use to control emissions from affected stationary sources. Stationary sources, such as factories, are issued permits that define how much air pollution they can emit. In California, local air districts have the authority to grant permits to stationary sources, while CARB reviews and helps coordinate programs for California air districts.

Air districts regulate the emissions of criteria pollutants and toxic air contaminants by requiring all potential pollutant-emitting stationary sources to get a permit to construct and operate, unless explicitly exempted from permitting requirements. Permits issued by air districts outline all of the local, state, and federal rules that apply to each emission source, as well as any additional restrictions or emissions controls that must be enacted for the source. The amount of pollution that a source is permitted to emit is called the emission limit. There are numerous factors that can affect a source’s permitted emission limit, including the equipment type, it’s operational schedule, the specific activity the source is used for, and whether the permit is issued to a new, modified, or existing source.