Terminology Services

Ozone Layer Protection Glossary

Description:

Important terms and acronyms to help understand information about ozone depletion.

Publishing Organization:

Office of Air and Radiation/Office of Atmospheric Protection/Stratospheric Protection Division

Last Update:

March 24, 2016

Program Site:

https://www.epa.gov/ozone-layer-protection

Terms & Acronyms

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	Term
	Aerosol	Definition 1: A small droplet or particle suspended in the atmosphere, typically containing sulfur. Aerosols are emitted naturally (e.g., in volcanic eruptions) and as the result of human activities (e.g., by burning fossil fuels). There is no connection between particulate aerosols and pressurized products also called aerosols. (See alternative definition of "aerosol"). Definition 2: A product that relies on a pressurized gas to propel substances out of a container. Consumer aerosol products in the United States have not used ozone-depleting substances (ODS) since the late 1970s because of voluntary switching followed by federal regulation. The Clean Air Act and EPA regulations further restricted the use of ODS for non-consumer products. All consumer products, and most other aerosol products, now use propellants that do not deplete the ozone layer, such as hydrocarbons and compressed gases.
	Aerosols	Definition 1: A small droplet or particle suspended in the atmosphere, typically containing sulfur. Aerosols are emitted naturally (e.g., in volcanic eruptions) and as the result of human activities (e.g., by burning fossil fuels). There is no connection between particulate aerosols and pressurized products also called aerosols. (See alternative definition of "aerosol"). Definition 2: A product that relies on a pressurized gas to propel substances out of a container. Consumer aerosol products in the United States have not used ozone-depleting substances (ODS) since the late 1970s because of voluntary switching followed by federal regulation. The Clean Air Act and EPA regulations further restricted the use of ODS for non-consumer products. All consumer products, and most other aerosol products, now use propellants that do not deplete the ozone layer, such as hydrocarbons and compressed gases.
	Appliance	Definition: Any device which contains and uses a Class I (chlorofluorocarbon; CFC) or Class II (hydrochlorofluorocarbons; HCFC) substance as a refrigerant and which is used for household or commercial purposes, including any air conditioner, refrigerator, chiller, or freezer. EPA interprets this definition to include all air-conditioning and refrigeration equipment except that designed and used exclusively for military purposes.
	Appliances	Definition: Any device which contains and uses a Class I (chlorofluorocarbon; CFC) or Class II (hydrochlorofluorocarbons; HCFC) substance as a refrigerant and which is used for household or commercial purposes, including any air conditioner, refrigerator, chiller, or freezer. EPA interprets this definition to include all air-conditioning and refrigeration equipment except that designed and used exclusively for military purposes.
	Apprentice	Definition: Any person who is currently registered as an apprentice in service, maintenance, repair, or disposal of appliances with the U.S. Department of Labor's Bureau of Apprenticeship and Training (or a State Apprenticeship Council recognized by the Bureau of Apprenticeship and Training).
	Carbon Tetrachloride	Definition: A compound consisting of one carbon atom and four chlorine atoms. Carbon tetrachloride was widely used as a raw material in many industrial uses, including the production of chlorofluorocarbons and as a solvent. Solvent use ended when it was discovered to be carcinogenic. It is also used as a catalyst to deliver chlorine ions to certain processes. Its ozone depletion potential is 1.2. Acronym: CCl4
	Chlorofluorocarbon	Definition: A compound consisting of chlorine, fluorine, and carbon. Chlorofluorocarbons (CFCs) are very stable in the troposphere. They move to the stratosphere and are broken down by strong ultraviolet light, where they release chlorine atoms that then deplete the ozone layer. CFCs were commonly used as refrigerants, solvents, and foam blowing agents. The most common CFCs were CFC-11, CFC-12, CFC-113, CFC-114, and CFC-115. CFCs have been phased out in the United States, with a few exceptions. Acronym: CFC
	Chlorofluorocarbons	Definition: A compound consisting of chlorine, fluorine, and carbon. Chlorofluorocarbons (CFCs) are very stable in the troposphere. They move to the stratosphere and are broken down by strong ultraviolet light, where they release chlorine atoms that then deplete the ozone layer. CFCs were commonly used as refrigerants, solvents, and foam blowing agents. The most common CFCs were CFC-11, CFC-12, CFC-113, CFC-114, and CFC-115. CFCs have been phased out in the United States, with a few exceptions. Acronym: CFCs
	Class I Ozone-Depleting Substance	Definition: One of several groups of chemicals with an ozone-depletion potential of 0.2 or higher. Class I ozone-depleting substances listed in the Clean Air Act include chlorofluorocarbons, halons, carbon tetrachloride, methyl chloroform hydrobromofluorocarbons, and methyl bromide.
	Class I Ozone-Depleting Substances	Definition: One of several groups of chemicals with an ozone-depletion potential of 0.2 or higher. Class I ozone-depleting substances listed in the Clean Air Act include chlorofluorocarbons, halons, carbon tetrachloride, methyl chloroform hydrobromofluorocarbons, and methyl bromide.
	Class II Ozone-Depleting Substance	Definition: A chemical with an ozone-depletion potential of less than 0.2. Currently, all hydrochlorofluorocarbons are Class II ozone-depleting substances.
	Class II Ozone-Depleting Substances	Definition: A chemical with an ozone-depletion potential of less than 0.2. Currently, all hydrochlorofluorocarbons are Class II ozone-depleting substances.
	Clean Air Act	Definition: A law amended by Congress in 1990. Title VI of the Clean Air Act directs EPA to protect the ozone layer through several regulatory and voluntary programs. Sections within Title VI cover production of ozone-depleting substances (ODS), the recycling and handling of ODS, the evaluation of substitutes, and efforts to educate the public. Acronym: CAA
	Column Ozone	Definition: The amount of ozone in a vertical column of air extending from the Earth's surface to outer space, typically measured using the Dobson Unit.
	Critical Use	Definition: Critical use means a circumstance in which the following two conditions are satisfied: (1) There are no technically and economically feasible alternatives or substitutes for methyl bromide available that are acceptable from the standpoint of environment and health and are suitable to the crops and circumstances involved, and (2) The lack of availability of methyl bromide for a particular use would result in significant market disruption.
	Critical Uses	Definition: Critical use means a circumstance in which the following two conditions are satisfied: (1) There are no technically and economically feasible alternatives or substitutes for methyl bromide available that are acceptable from the standpoint of environment and health and are suitable to the crops and circumstances involved, and (2) The lack of availability of methyl bromide for a particular use would result in significant market disruption.
	Destruction	Definition: The expiration of a controlled substance to the destruction efficiency actually achieved, unless considered completely destroyed as defined in this section. Such destruction does not result in a commercially useful end product and uses one of the following controlled processes approved by the Parties to the Protocol: (1) Liquid injection incineration; (2) Reactor cracking; (3) Gaseous/fume oxidation; (4) Rotary kiln incineration; (5) Cement kiln; (6) Radio frequency plasma; or (7) Municipal waste incinerators only for the destruction of foams.
	Dobson Unit	Definition: A measurement of column ozone levels, or how much ozone is in a vertical column of air. If 100 Dobson Units (DUs) of ozone were brought to the Earth's surface, it would form a layer 1 millimeter thick. Above the tropics, ozone levels are typically between 250 and 300 DU year-round. In temperate regions, seasonal variations can produce large swings in ozone levels. For instance, measurements in Leningrad have recorded ozone levels as high as 475 DU and as low as 300 DU. The DU is just one of many methods to measure ozone. Other measures include partial pressure, number density, and concentration of ozone, and can represent either column ozone or the amount of ozone at a particular altitude.
	Essential Uses	Definition: Those uses of controlled substances designated by the Parties to the Montreal Protocol to be necessary for the health and safety of, or critical for the functioning of, society; and for which there are no available technically and economically feasible alternatives or substitutes that are acceptable from the standpoint of environment and health. Beginning January 1, 2000 (January 1, 2002 for methyl chloroform) the essential use designations for Class I ozone-depleting substances must be made in accordance with the provisions of the Clean Air Act Amendments of 1990.
	Global Warming Potential	Definition: A number that refers to the amount of global warming caused by a substance. The GWP is the ratio of the warming caused by a substance to the warming caused by a similar mass of carbon dioxide (CO2). Thus, the GWP of CO2 is 1.0. Chlorofluorocarbon (CFC)-12 has a GWP of 8,500; CFC-11 has a GWP of 5,000; hydrochlorofluorocarbons and hydrofluorocarbons have GWPs ranging from 93 to 12,100; and water has a GWP of 0. Acronym: GWP
	Global Warming Potentials	Definition: A number that refers to the amount of global warming caused by a substance. The GWP is the ratio of the warming caused by a substance to the warming caused by a similar mass of carbon dioxide (CO2). Thus, the GWP of CO2 is 1.0. Chlorofluorocarbon (CFC)-12 has a GWP of 8,500; CFC-11 has a GWP of 5,000; hydrochlorofluorocarbons and hydrofluorocarbons have GWPs ranging from 93 to 12,100; and water has a GWP of 0. Acronym: GWPs
	Halon	Definition: A compound consisting of bromine, fluorine, and carbon. Halons are used as fire extinguishing agents, both in built-in systems and in handheld portable fire extinguishers. Halon production in the U.S. ended on December 31, 1993, because they contribute to ozone depletion.
	Heel	Definition: The residual amount of a substance that remains in a container after it is discharged or offloaded. By law, a heel can be no more than ten percent of the volume of the container. The person importing the heel must certify that the residual amount will remain in the container and be included in a future shipment, or be recovered for transformation, destruction, or a non-emissive purpose.
	Hydrobromofluorocarbon	Definition: An ozone-depleting substance consisting of hydrogen, bromine, fluorine, and carbon. Acronym: HBFC
	Hydrobromofluorocarbons	Definition: An ozone-depleting substance consisting of hydrogen, bromine, fluorine, and carbon. Acronym: HBFCs
	Hydrocarbon	Definition: A compound consisting of carbon and hydrogen. Hydrocarbons include methane, ethane, propane, cyclopropane, butane, and cyclopentane. Although they are flammable, hydrocarbons (HCs) may offer advantages as substitutes to ozone-depleting substances because they have zero ozone depletion potential, low toxicity, and with the exception of methane, have low global warming potentials. Acronym: HC
	Hydrocarbons	Definition: A compound consisting of carbon and hydrogen. Hydrocarbons include methane, ethane, propane, cyclopropane, butane, and cyclopentane. Although they are flammable, hydrocarbons (HCs) may offer advantages as substitutes to ozone-depleting substances because they have zero ozone depletion potential, low toxicity, and with the exception of methane, have low global warming potentials. Acronym: HCs
	Hydrochlorofluorocarbon	Definition: A compound consisting of hydrogen, chlorine, fluorine, and carbon. Hydrochlorofluorocarbons (HCFCs) are one class of chemicals that was used to replace the chlorofluorocarbons (CFCs). They contain chlorine and thus deplete stratospheric ozone, but to a much lesser extent than CFCs. HCFCs have ozone depletion potentials (ODPs) ranging from 0.01 to 0.1. Production of HCFCs is being phased out. Acronym: HCFC
	Hydrochlorofluorocarbons	Definition: A compound consisting of hydrogen, chlorine, fluorine, and carbon. Hydrochlorofluorocarbons (HCFCs) are one class of chemicals that was used to replace the chlorofluorocarbons (CFCs). They contain chlorine and thus deplete stratospheric ozone, but to a much lesser extent than CFCs. HCFCs have ozone depletion potentials (ODPs) ranging from 0.01 to 0.1. Production of HCFCs is being phased out. Acronym: HCFCs
	Hydrofluorocarbon	Definition: A compound consisting of hydrogen, fluorine, and carbon. Hydrofluorocarbons (HFCs) are a class of replacements for chlorofluorocarbons. Because they do not contain chlorine or bromine, they do not deplete the ozone layer. All HFCs have an ozone depletion potential of 0. Some HFCs have high global warming potentials. Acronym: HFC
	Hydrofluorocarbons	Definition: A compound consisting of hydrogen, fluorine, and carbon. Hydrofluorocarbons (HFCs) are a class of replacements for chlorofluorocarbons. Because they do not contain chlorine or bromine, they do not deplete the ozone layer. All HFCs have an ozone depletion potential of 0. Some HFCs have high global warming potentials. Acronym: HFCs
	Hydrofluoroolefin	Definition: A compound consisting of hydrogen, fluorine, and carbon. Hydrofluoroolefins (HFOs) are alternatives to ozone-depleting substances that typically have very low global warming potentials. Acronym: HFO
	Hydrofluoroolefins	Definition: A compound consisting of hydrogen, fluorine, and carbon. Hydrofluoroolefins (HFOs) are alternatives to ozone-depleting substances that typically have very low global warming potentials. Acronym: HFOs
	Major Maintenance, Service, or Repair	Definition: Maintenance, service, or repair that involves removal of the appliance compressor, condenser, evaporator, or auxiliary heat exchanger coil.
	Methyl Bromide	Definition: A compound consisting of carbon, hydrogen, and bromine. Methyl Bromide (MeBr) is an effective pesticide used to fumigate soil and many agricultural products. Because it contains bromine, it depletes stratospheric ozone. MeBr has an ozone depletion potential of 0.6. Production of methyl bromide was phased out on December 31, 2004, except for allowable exemptions. Acronym: MeBr
	Methyl Chloroform	Definition: A compound consisting of carbon, hydrogen, and chlorine. Methyl chloroform is used as an industrial solvent. Its ozone depletion potential is 0.11. Acronym: CH3CCl3
	Montreal Protocol	Definition: The international treaty governing the protection of stratospheric ozone. The Montreal Protocol on Substances That Deplete the Ozone Layer and its amendments control the phaseout of ozone-depleting substance (ODS) production and use. Under the Montreal Protocol, several international organizations report on the science of ozone depletion, implement projects to help move away from ODS, and provide a forum for policy discussions. In addition, the Multilateral Fund provides resources to developing nations to promote the transition to ozone-safe technologies.
	Motor Vehicle Air Conditioner-Like Appliance	Definition: Mechanical vapor compression, open-drive compressor appliances used to cool the driver's or passenger's compartment of a non-road vehicle, including agricultural and construction vehicles. This definition excludes appliances using hydrochlorofluorocarbon-22 (also called R-22). Acronym: MVAC-Like Appliance
	Motor Vehicle Air Conditioner-Like Appliances	Definition: Mechanical vapor compression, open-drive compressor appliances used to cool the driver's or passenger's compartment of a non-road vehicle, including agricultural and construction vehicles. This definition excludes appliances using hydrochlorofluorocarbon-22 (also called R-22). Acronym: MVAC-Like Appliances
	Nanometer	Definition: A distance of one billionth of a meter. The nanometer (nm) is a common unit used to describe wavelengths of light or other electromagnetic radiation such as ultraviolet radiation. For example, green light has wavelengths of about 500-550 nm, while violet light has wavelengths of about 400-450 nm. Acronym: nm
	Nanometers	Definition: A distance of one billionth of a meter. The nanometer (nm) is a common unit used to describe wavelengths of light or other electromagnetic radiation such as ultraviolet radiation. For example, green light has wavelengths of about 500-550 nm, while violet light has wavelengths of about 400-450 nm. Acronym: nm
	Opening	Definition: Any service, maintenance, or repair on an appliance that would release Class I or Class II refrigerant from the appliance to the atmosphere unless the refrigerant were recovered previously from the appliance. Connecting and disconnecting hoses and gauges to and from the appliance to measure pressures within the appliance and to add refrigerant to or recover refrigerant from the appliance shall not be considered "opening."
	Ozone	Definition: A gas composed of three atoms of oxygen. Ozone is a bluish gas that is harmful to breathe. Nearly 90% of the Earth's ozone is in the stratosphere and is referred to as the ozone layer. Ozone absorbs a band of ultraviolet radiation called UVB that is particularly harmful to living organisms. The ozone layer prevents most UVB from reaching the ground.
	Ozone-Depleting Substance	Definition: A compound that contributes to stratospheric ozone depletion. Ozone-depleting substances (ODS) include chlorofluorocarbons, hydrochlorofluorocarbons, halons, methyl bromide, carbon tetrachloride, hydrobromofluorocarbons, chlorobromomethane, and methyl chloroform. ODS are generally very stable in the troposphere and only degrade under intense ultraviolet light in the stratosphere. When they break down, they release chlorine or bromine atoms, which then deplete ozone. Acronym: ODS
	Ozone-Depleting Substances	Definition: A compound that contributes to stratospheric ozone depletion. Ozone-depleting substances (ODS) include chlorofluorocarbons, hydrochlorofluorocarbons, halons, methyl bromide, carbon tetrachloride, hydrobromofluorocarbons, chlorobromomethane, and methyl chloroform. ODS are generally very stable in the troposphere and only degrade under intense ultraviolet light in the stratosphere. When they break down, they release chlorine or bromine atoms, which then deplete ozone. Acronym: ODS
	Ozone Depletion Potential	Definition: A number that refers to the amount of ozone depletion caused by a substance. The ODP is the ratio of the impact on ozone of a chemical compared to the impact of a similar mass of chlorofluorocarbon (CFC)-11. Thus, the ODP of CFC-11 is 1.0. Other CFCs and hydrochlorofluorocarbon have ODPs that range from 0.01 to 1.0. Halon ODPs peak at 10. Carbon tetrachloride has an ODP of 1.2, and methyl chloroform's ODP is 0.11. Hydrofluorocarbons have zero ODP because they do not contain chlorine. Acronym: ODP
	Ozone "Hole"	Definition: A large area of the stratosphere with extremely low amounts of ozone.
	Ozone Layer	Definition: The region of the stratosphere containing the bulk of atmospheric ozone. The ozone layer lies approximately 15-40 kilometers (10-25 miles) above the Earth's surface, in the stratosphere. Depletion of this layer by ozone-depleting substances will lead to higher UVB levels (a band of ultraviolet radiation), which in turn will cause increased skin cancers and cataracts and potential damage to some marine organisms, plants, and plastics.
	Ozone Layer Depletion	Definition: Chemical destruction of ozone molecules in the ozone layer.
	Perfluorocarbon	Definition: A compound consisting of carbon and fluorine. Perfluorocarbons (PFCs) have extremely high global warming potentials and very long lifetimes. They do not deplete stratospheric ozone, but EPA is concerned about their impact on global warming. Acronym: PFC
	Perfluorocarbons	Definition: A compound consisting of carbon and fluorine. Perfluorocarbons (PFCs) have extremely high global warming potentials and very long lifetimes. They do not deplete stratospheric ozone, but EPA is concerned about their impact on global warming. Acronym: PFCs
	Reclaim	Definition: To reprocess refrigerant to at least the purity specified in the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) Standard 700-1995 and to verify this purity using the analytical methodology prescribed in the standard. Reclamation requires specialized machinery not available at a particular job site or auto repair shop. The technician will recover the refrigerant and then send it either to a general reclaimer or back to the refrigerant manufacturer.
	Recover	Definition: To remove refrigerant in any condition from an appliance and store it in an external container without necessarily testing or processing it in any way.
	Recycle	Definition: To extract refrigerant from an appliance and clean refrigerant for reuse without meeting all of the requirements for reclamation. In general, recycled refrigerant is refrigerant that is cleaned using oil separation and single or multiple passes through devices, such as replaceable core filter-driers, which reduce moisture, acidity, and particulate matter. Under Section 609 of the Clean Air Act, refrigerant can be removed from one car's air conditioner, recycled on site, and then charged into a different car.
	Refrigerant Circuit	Definition: The parts of an appliance that are normally connected to each other (or are separated only by internal valves) and are designed to contain refrigerant.
	Small Appliance	Definition: Any of the following products that are fully manufactured, charged, and hermetically sealed in a factory with five pounds or less of refrigerant: refrigerators and freezers designed for home use, room air conditioners (including window air conditioners and packaged terminal air conditioners), packaged terminal heat pumps, dehumidifiers, under-the-counter ice makers, vending machines, and drinking water coolers.
	Small Appliances	Definition: Any of the following products that are fully manufactured, charged, and hermetically sealed in a factory with five pounds or less of refrigerant: refrigerators and freezers designed for home use, room air conditioners (including window air conditioners and packaged terminal air conditioners), packaged terminal heat pumps, dehumidifiers, under-the-counter ice makers, vending machines, and drinking water coolers.
	Stratosphere	Definition: The region of the atmosphere above the troposphere. The stratosphere extends from about 10-50 km (6-31 miles) in altitude. Commercial airlines fly in the lower stratosphere. The stratosphere gets warmer at higher altitudes. In fact, this warming is caused by ozone absorbing ultraviolet radiation. Warm air remains in the upper stratosphere, and cool air remains lower, so there is much less vertical mixing in this region than in the troposphere.
	Technician	Definition: Any person who performs maintenance, service, or repair that could reasonably be expected to release Class I or Class II substances from appliances, except for MVACs, into the atmosphere. Technician also means any person performing disposal of appliances, except for small appliances, MVACs, and MVAC-like appliances, that could be reasonably expected to release Class I or Cass II refrigerants from appliances into the atmosphere.
	Technicians	Definition: Any person who performs maintenance, service, or repair that could reasonably be expected to release Class I or Class II substances from appliances, except for MVACs, into the atmosphere. Technician also means any person performing disposal of appliances, except for small appliances, MVACs, and MVAC-like appliances, that could be reasonably expected to release Class I or Cass II refrigerants from appliances into the atmosphere.
	Transform	Definition: To use and entirely consume (except for trace quantities) a controlled substance in the manufacture of other chemicals for commercial purposes.
	Transhipment	Definition: The continuous shipment of a controlled substance (e.g., chlorofluorocarbons), from a foreign state of origin through the United States or its territories, to a second foreign state of final destination, as long as the shipment does not enter into United States jurisdiction. A transshipment, may not be re-packaged, sorted, or otherwise changed in condition as it moves through the United States or its territories.
	Troposphere	Definition: The region of the atmosphere closest to the Earth. The troposphere extends from the surface up to about 10 km (6 miles) in altitude, although this height varies with latitude. Almost all weather takes place in the troposphere. Mt. Everest, the highest mountain on Earth, is only 8.8 km (5.5 miles) high. Temperatures decrease with altitude in the troposphere. As warm air rises, it cools, falling back to Earth. This process, known as convection, means there are huge air movements that mix the troposphere very efficiently.
	Ultraviolet Radiation	Definition: Ultraviolet radiation is a portion of the electromagnetic spectrum with wavelengths shorter than visible light. The sun produces UV, which is commonly split into three bands: UVA, UVB, and UVC. UVA is not absorbed by ozone. UVB is mostly absorbed by ozone, although some reaches the Earth. UVC is completely absorbed by ozone and normal oxygen. Acronym: UV
	Used Controlled Substances	Definition: A used Class I or Class II compound that has been either recovered from its intended use systems (e.g., chiller, refrigerator, etc.) or has been recycled or reclaimed.
	UVA	Definition: A band of ultraviolet radiation with wavelengths from 320-400 nanometers produced by the Sun. UVA is not absorbed by ozone. This band of radiation has wavelengths just shorter than visible violet light.
	UVB	Definition: A band of ultraviolet radiation with wavelengths from 280-320 nanometers produced by the Sun. UVB is a kind of ultraviolet light from the sun (and sun lamps) that has several harmful effects. UVB is particularly effective at damaging DNA. It is a cause of melanoma and other types of skin cancer. It has also been linked to damage to some materials, crops, and marine organisms. The ozone layer protects the Earth against most UVB coming from the sun. It is always important to protect oneself against UVB, even in the absence of ozone depletion, by wearing hats, sunglasses, and sunscreen. However, these precautions will become more important as ozone depletion worsens.
	UVC	Definition: A band of ultraviolet radiation with wavelengths shorter than 280 nanometers. UVC is extremely dangerous, but it is completely absorbed by ozone and normal oxygen (O2).

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