Forest Trail


17 results found for



The act of burning a material to ashes.

Incremental Reactivity (IR)

The additional ozone formed in the atmosphere with the incremental addition of a certain amount of a volatile organic compound.

Indirect Source

Any facility, building, structure, or installation, or combination thereof, which generates or attracts mobile source activity that results in emissions of any pollutant (or precursor) for which there is a state ambient air quality standard. Examples of indirect sources include employment sites, shopping centers, sports facilities, housing developments, airports, commercial and industrial development and parking lots and garages.

Indirect Source Control Program

Rules, regulations, local ordinances and land use controls and other regulatory strategies of air pollution control districts or local governments used to control or reduce emissions associated with new and existing indirect sources. Indirect source control programs include regulatory strategies such as transportation control measures (e.g., South Coast's Regulation XV for employer-based trip reduction); parking charges; land use controls that reduce the need for vehicle travel and increase transit, bicycle and pedestrian access; and, source-specific regulations such as truck idling and travel schedule requirements.

Indirect Source Review

A major component of an indirect source control program which applies to new and modified indirect sources. Strategies for indirect source review include permit programs, review and comment on new and modified indirect source projects through the California Environmental Quality Act (CEQA) process and coordination of air quality, transportation and land use policies through local government general plans. Indirect source review reduces emissions from new and modified sources through best available mitigation measures and additional offsite mitigation such as offsets and mitigation fees.

Individual Cancer Risk

The probability, expressed as chances in a million, that a person experiencing 70 years of continuous area-wide outdoor exposure to a toxic air contaminant will develop cancer.

Indoor Air Pollution

Air pollutants that occur within buildings or other enclosed spaces, as opposed to those occurring in outdoor, or ambient air. Some examples of indoor air pollutants are nitrogen oxides, smoke, asbestos, formaldehyde and carbon monoxide. For more information, visit our indoor air quality website.

Industrial Source

Any of a large number of sources -- such as manufacturing operations, oil and gas refineries, food processing plants and energy generating facilities -- that emit substances into the atmosphere.

Inert Gas

A gas that does not react with the substances coming in contact with it.

Innovative Clean Air Technologies program (ICAT)

ICAT is an ARB program that co-funds the demonstration of innovative technologies that can reduce air pollution. Its purpose is to advance such technologies toward commercial application, thereby reducing emissions and helping the economy of California.

Inspection and Maintenance Program (I/M Program)

A motor vehicle inspection program implemented by the California Bureau of Automotive Repair. The purpose of the I/M is to reduce emissions by assuring that cars are running properly. It is designed to identify vehicles in need of maintenance and to assure the effectiveness of their emission control systems on a biennial basis. Enacted in 1979 and strengthened in 1990. (Also known as the "Smog Check" program.)

I/M Program
Integrated Sampling Device

An air sampling device that allows estimation of air quality components over a period of time through laboratory analysis of the sampler's medium. (See also Continuous Sampling Device.)

Intergovernmental Panel on Climate Change (IPCC)

A scientific intergovernmental body set up by the World Meteorological Organization (WMO) and by the United Nations Environment Programme (UNEP) to provide the decision-makers and others interested in climate change with an objective source of information about climate change.

Internal Combustion Engine

An engine in which both the heat energy and the ensuing mechanical energy are produced inside the engine. Includes gas turbines, spark ignition gas and compression ignition diesel engines.

International Agency for Research on Cancer (IARC)

An expert international agency of the World Health Organization which publishes evaluations of evidence on the carcinogenicity of a wide range of chemicals. For more information, visit our IARC website.


A layer of warm air in the atmosphere that prevents the rise of cooling air and traps pollutants beneath it.

Investor Owned Utilities (IOUs)

Private companies that provide a utility, such as water, natural gas or electricity, to a specific service area.