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California Air Pollution Control Officers Association (CAPCOA)

A nonprofit association of the air pollution control officers from all 35 air quality agencies throughout California. CAPCOA was formed in 1975 to promote clean air and to provide a forum for sharing of knowledge, experience and information among the air quality regulatory agencies around the state. CAPCOA is an organization of air quality professionals -- leaders in their field -- who promote unity and efficiency and strive to encourage consistency in methods and practices of air pollution control. For more information, visit our CAPCOA's website.

California Air Resources Board (ARB or CARB)

The state's lead air quality agency consisting of an 11-member board appointed by the Governor, and just over thousand employees. ARB is responsible for attainment and maintenance of the state and federal air quality standards, California climate change programs, and is fully responsible for motor vehicle pollution control. It oversees county and regional air pollution management programs.

California Ambient Air Quality Standard (CAAQS)

A legal limit that specifies the maximum level and time of exposure in the outdoor air for a given air pollutant and which is protective of human health and public welfare. CAAQSs are recommended by the OEHHA and adopted into regulation by the ARB. CAAQSs are the standards which must be met per the requirements of the California Clean Air Act (CCAA).

California Clean Air Act (CCAA)

A California law passed in 1988 which provides the basis for air quality planning and regulation independent of federal regulations. A major element of the Act is the requirement that local air districts in violation of the CAAQS must prepare attainment plans that identify air quality problems, causes, trends and actions to be taken to attain and maintain California's air quality standards by the earliest practicable date.

California Environmental Protection Agency (Cal/EPA)

A state government agency established in 1991 for unifying environmental activities related to public health protection in the State of California. There are five boards, departments and offices under the organization of Cal/EPA including the California Air Resources Board (ARB), State Water Resources Control Board (SWRCB) and its nine Regional Water Quality Control Boards (RWQCB), Department of Pesticide Regulation (DPR), Department of Toxic Substances Control (DTSC) and Office of Environmental Health Hazard Assessment (OEHHA). The Cal/EPA boards, departments and offices are directly responsible for implementing California environmental laws, or play a cooperative role with other regulatory agencies at regional, local, state and federal levels. For a full list of Cal/EPA organizations, see Cal/EPA's home page.

California Environmental Quality Act (CEQA)

A California law that sets forth a process for public agencies to make informed decisions on discretionary project approvals. The process aids decision-makers to determine whether any environmental impacts are associated with a proposed project. It requires environmental impacts associated with a proposed project to be eliminated or reduced and that air quality mitigation measures are implemented.

California Hydrogen Highway Network (CaH2Net)

An initiative to add hydrogen fueling infrastructure in California to meet the demands of hydrogen vehicles deployed in the state.P For more information, visit the California Hydrogen Highway Network website.

California Phase 2 Reformulated Gasoline (CaRFG Phase 2 or CaRFG2)

Gasoline sold, intended for sale, or made available for sale as a motor vehicle fuel in California subject to the California Phase 2 reformulated gasoline standards.

CaRFG Phase 2, CaRFG2
California Phase 3 Reformulated Gasoline (CaRFG Phase 3 or CaRFG3)

Gasoline sold, intended for sale, or made available for sale as a motor vehicle fuel in California subject to the California Phase 3 reformulated gasoline standards.

CaRFG Phase 3, CaRfg3
California reformulated gasoline blendstock for oxygenate blending (CARBOB)

A petroleum-derived liquid that is intended to be a product that will become California reformulated gasoline upon the addition of an oxygenate, such as ethanol.

California Solar Initiative (CSI)

A California Public Utilities Commission investor-owned utility program initiated on January 1, 2007, to provide incentives for installing solar distributed generation projects.


A group of diseases characterized by uncontrolled invasive growth of body cells leading to the formation of malignant tumors that tend to grow rapidly and spread (i.e., metastasize).


An enforceable limit on total emissions for the facilities covered under the cap-and-trade program. The cap is set for each compliance period of the program by the state and emissions are reduced as the cap declines over time.


Cap-and-trade is a regulatory approach used to control pollution by setting a firm cap on allowed emissions while employing market mechanisms to achieve emissions reductions while driving costs down. In a cap-and-trade program, a limit, or cap is put on the amount of greenhouse gases that can be emitted.

CARB gasoline, California Reformulated Gasoline (CaRFG)

Gasoline sold, intended for sale, or made available for sale as a motor vehicle fuel in California subject to the California reformulated gasoline standards.

Carbon Capture and Sequestration (CCS)

The process of capturing CO2 from a stationary source, followed by compressing, transporting and injecting it into a suitable geologic formation where it will be sequestered.

Carbon Dioxide (CO2)

A colorless, odorless gas that occurs naturally in the Earth's atmosphere. Significant quantities are also emitted into the air by fossil fuel combustion. (See also gloss.)

Carbon Dioxide Equivalent (CO2E)

The amount of carbon dioxide by weight that would produce the same global warming impact as a given weight of another greenhouse gas, based on the best available science, including from the Intergovernmental Panel on Climate Change.

Carbon Monoxide (CO)

A colorless, odorless gas resulting from the incomplete combustion of hydrocarbon fuels. CO interferes with the blood's ability to carry oxygen to the body's tissues and results in numerous adverse health effects. Over 80 percent of the CO emitted in urban areas is contributed by motor vehicles. CO is a criteria air pollutant.

Carbon Sequestration

The process of removing carbon dioxide (CO2) from the atmosphere by storing it in a carbon reservoir other than the atmosphere. Sequestration enhances carbon storage in trees and soils, preserves existing tree and soil carbon and reduces emissions of CO2, methane (CH4) and nitrous oxide (N2O).


A cancer-causing substance. (See also cancer)

Carl Moyer Fund

A multi-million dollar incentive grant program designed to encourage reduction of emissions from heavy-duty engines. The grants cover the additional cost of cleaner technologies for on-road, off-road, marine, locomotive and agricultural pump engines, as well as forklifts and airport ground support equipment.

CAS Registry Number

The Chemical Abstracts Service Registry Number (CAS) is a numeric designation assigned by the American Chemical Society's Chemical Abstract Service and uniquely identifies a specific compound. This entry allows one to conclusively identify a material regardless of the name or naming system used.


A substance that can increase or decrease the rate of a chemical reaction between the other chemical species without being consumed in the process.

Catalytic Converter

A motor vehicle pollution control device designed to reduce emissions such as oxides of nitrogen, hydrocarbons and carbon monoxide. Catalytic converters have been required equipment on all new motor vehicles sold in California since 1979.

Certified, Certification

The formal process where the manufacturer of a vehicle, product, or process demonstrates compliance with all applicable regulations and is granted permission to market, sell, or deliver the item in California. Certification in California is usually indicated by the granting of an Executive Order (EO).

Chlorofluorocarbons (CFCs)

Any of a number of substances consisting of chlorine, fluorine and carbon. CFCs are used for refrigeration, foam packaging, solvents and propellants.


See Combined Heat and Power.

Chronic Exposure

Long-term exposure, usually lasting one year to a lifetime.

Chronic Health Effect

A health effect that occurs over a relatively long period of time (e.g., months or years). (See also acute health effect.)

Chronic Obstructive Pulmonary Disease (COPD)

COPD is a lung disease characterized by chronic obstruction of airflow that interferes with normal breathing and is generally progressive, but may be partially reversible. The more familiar terms 'chronic bronchitis' and 'emphysema' are included within the COPD diagnosis. COPD is strongly associated with tobacco smoking but can occur in non-smokers as well and is a serious, life-threatening lung disease.

Clean Vehicle Rebate Project (CVRP)

CVRP is intended to encourage and accelerate zero-emission vehicle deployment and technology innovation by providing grants to eligible vehicles. For more details see the ARB website.

Cleaner-Burning Gasoline

Gasoline fuel that results in reduced emissions of carbon monoxide, nitrogen oxides, reactive organic gases and particulate matter, in addition to toxic substances such as benzene and 1,3-butadiene. Visit our cleaner-burning gasoline website or an overview of ARB's fuels program.

Climate Action Team (CAT)

The Secretary of Cal/EPA leads the Climate Action Team made up of representatives from state agencies, boards and departments. The CAT members work to coordinate statewide efforts to implement global warming emission reduction programs and the state's Climate Adaptation Strategy. The CAT is also responsible for reporting on the progress made toward meeting the statewide greenhouse gas targets that were established by Executive Order S-3-05 and further defined under AB 32.

Climate Change

see Global Warming and/or its own glossary.


A layer of any substance such as paint, lacquer, or varnish applied over a surface for protection. For more information, visit our coatings website.

Coefficient of Haze (COH)

A measurement of the quantity of dust and smoke in the atmosphere in a theoretical 1,000 linear feet of air. A COH of less than three is considered clean air and more than five is of some concern. COH readings of 20 or more can occur in urban areas.

Cold Ironing

Cold Ironing or Shore power refers to providing electrical power to a vessel that is docked. The purpose of shore power is to allow the vessel operator to turn off the vessel's auxiliary engines, which would normally be providing the necessary electricity. Although there are emissions associated with the generation of electricity used for shore power, those emissions are much less than those from the auxiliary engines, which burn diesel fuel.

Combined Heat and Power (CHP)

An approach to generating power and thermal energy from a single fuel source. CHP application involves the recovery of otherwise wasted thermal energy to produce additional power or useful thermal energy.


The act or instance of burning some type of fuel, such as gasoline, to produce energy. Combustion is typically the process that powers automobile engines and power plant generators.

Compressed Natural Gas (CNG)

(See alternative fuels.)


A demonstration of whether a federally-supported activity is consistent with the State Implementation Plan (SIP) -- per Section 176 (c) of the Clean Air Act. Transportation conformity refers to plans, programs and projects approved or funded by the Federal Highway Administration or the Federal Transit Administration. General conformity refers to projects approved or funded by other federal agencies.

Congestion Management Program

A state-mandated program (California Government Code Section 65089a) that requires each county to prepare a plan to relieve congestion and reduce air pollution.

Consumer Products

Products such as hairspray, detergents, cleaning compounds, polishes, lawn and garden products, personal care products and automotive specialty products that are part of our everyday lives and, through consumer use, may produce volatile organic air emissions which contribute to air pollution.

Continuous Emission Monitor (CEM)

CEM involves determining compliance of stationary sources with their emission limitations on a continuous basis by installing a system to operate continuously inside of the smokestack or other emission source. CEM are also used for process control and to monitor the operations of the control equipment.

Continuous Sampling Device

An air analyzer that measures air quality components continuously. (See also Integrated Sampling Device.)

Control Techniques Guidelines (CTG)

Guidance documents issued by U.S. EPA that define reasonably available control technology (RACT) to be applied to existing facilities that emit excessive quantities of air pollutants; they contain information both on the economic and technological feasibility of available techniques.


The cost of an emission control measure assessed in terms of dollars-per-pound, or dollars-per-ton, of air emissions reduced

Criteria Air Pollutant

An air pollutant for which acceptable levels of exposure can be determined and for which an ambient air quality standard has been set. Examples include: ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, PM10 and PM2.5. The term "criteria air pollutants" derives from the requirement that the U.S. EPA must describe the characteristics and potential health and welfare effects of these pollutants. The U.S. EPA and ARB periodically review new scientific data and may propose revisions to the standards as a result.


An air pollution control device that removes larger particles -- generally greater than one micron -- from an air stream through centrifugal force.