Emission Inventory

An emission inventory is an itemized list of pollutants in a given area for a specified time-period. Collecting emissions from previous and current years is a vital component in air quality planning for rule development and State Implementation Plan related modeling tasks.

Air pollution comes from many sources such as large industrial facilities, as well as things we use in our daily lives such as cars and trucks, paints, and aerosol spray products. Sources of air pollution are categorized into four source emission types: point, areawide, mobile, or natural sources. Point emission sources are stationary source equipment that require a District permit. This source type could include combustion engines and boilers, refineries, gas stations, dry cleaners and industrial plants. Areawide source emissions are from sources that are not regulated by the District, or are individually so small that they may not be included in our survey system. Examples of these areawide sources are residential water heating and use of paints, varnishes, and consumer products.  The District is responsible for collecting and submitting point and certain areawide source inventories to the California Air Resources Board (CARB).

Mobile sources consist of on-road motor vehicles and off-road mobile transportation and equipment. In addition to man-made air pollution, there are significant quantities of pollutants emitted from natural sources. Natural emission sources include biological and geological sources, wildfires, windblown dust, and biogenic emissions from plants and trees.  CARB is responsible for collecting these mobile and natural source emission inventories for the state.  For more information on mobile and natural source emission inventories, please refer to CARB’s Emission Inventory webpage.