An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

The Accelerated Phaseout of Class I Ozone-Depleting Substances

Chlorofluorocarbons, halons, carbon tetrachloride, and methyl chloroform

On July 30, 1992, EPA issued a final rule 57 FR 33754 to limit the production and consumption of a set of chemicals known to deplete the stratospheric ozone layer. The rule required producers of Class I substances (chlorofluorocarbonsHelpchlorofluorocarbonsGases covered under the 1987 Montreal Protocol and used for refrigeration, air conditioning, packaging, insulation, solvents, or aerosol propellants. Since they are not destroyed in the lower atmosphere, CFCs drift into the upper atmosphere where, given suitable conditions, they break down ozone. These gases are being replaced by other compounds: hydrochlorofluorocarbons, an interim replacement for CFCs that are also covered under the Montreal Protocol, and hydrofluorocarbons, which are covered under the Kyoto Protocol. All these substances are also greenhouse gases. See hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, ozone depleting substance. [CFCs], halons, carbon tetrachlorideHelpcarbon tetrachlorideA 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 (CFCs), 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., and methyl chloroformHelpmethyl chloroformA compound consisting of carbon, hydrogen, and chlorine. Methyl chloroform is used as an industrial solvent. Its ozone depletion potential is 0.11.) to gradually reduce production of these chemicals and completely phase them out by January 1, 2000 (2002 for methyl chloroform).

On December 10, 1993, EPA announced in 58 FR 65018 that it would accelerate the phaseout date for the production of most Class I ozone-depleting substances (ODSHelpODSA compound that contributes to stratospheric ozone depletion. ODS include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), 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. A detailed list ( of class I and class II substances with their ODPs, GWPs, and CAS numbers are available.) from January 1, 2000, to December 31, 1995. EPA based this decision on scientific findings that these substances deplete the stratospheric ozone layer and responded to petitions from environmental and industry groups to accelerate their phaseout.

At the fourth meeting of the Parties to the Montreal ProtocolHelpMontreal ProtocolThe 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 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. The full text of the Montreal Protocol ( is available from the United Nations Environmental Programme (UNEP). in November 1992, the Parties agreed to accelerate the phaseout of CFCs, carbon tetrachloride, and methyl chloroform to the end of 1995 and halons to the end of 1993. In addition, the Parties agreed to add hydrobromofluorocarbonsHelphydrobromofluorocarbonA compound consisting of hydrogen, bromine, fluorine, and carbon. Although they were not originally regulated under the Clean Air Act, subsequent regulation added HBFCs to the list of class I substances. A table of class I substances (, shows their ODPs, GWPs, and CAS numbers. to the Class I list and phase them out by the end of 1995.

Methyl bromide

On February 11, 1992, the United States announced that it would consider the possible need to phase out methyl bromide. Starting in 1994, the United States froze the production and consumption at 1991 levels.

In revisions made to the Clean Air Act in 1998, the United States conformed its phaseout of methyl bromide to the Montreal Protocol phaseout. Learn more about methyl bromide and its phaseout schedule.

Additional Adjustments to the Phaseout

  • Inadvertent or coincidental production. EPA regulations permit the inadvertent or coincidental production of trace quantities of ODS during a manufacturing process.
  • Transformation or destruction processes. EPA regulations permit the production of controlled substances for transformation or destruction outside of the production and consumption allowance requirements, if the destruction is achieved by one of the processes approved by the Parties to the Montreal Protocol: liquid injection incineration, reactor cracking, gaseous/fume oxidation, rotary kiln incineration, and cement kilns.
    Learn more about ODS destruction and transformation.
  • Transhipment. The transhipment of bulk controlled chemicals from one foreign country to another through the United States does not count as consumption by the United States.
  • Importation. The import and export of recycled or used controlled substances does not count as consumption by the United States.
  • Feedstock. EPA regulations exempt controlled substances used for feedstock purposes from the requirements. No allowances are needed when producing or importing these substances for feedstock uses.
  • Trade limitation. EPA prohibits the trade of bulk controlled substances and products containing controlled substances with countries that are not Parties to the Montreal Protocol.