EPA regulations issued under Sections 601–607 of the Clean Air Act phase out the production and import of ozone-depleting substances (ODSODSA family of man-made compounds that includes, but are not limited to, chlorofluorocarbons (CFCs), bromofluorocarbons (halons), methyl chloroform, carbon tetrachloride, methyl bromide, and hydrochlorofluorocarbons (HCFCs). These compounds have been shown to deplete stratospheric ozone, and therefore are typically referred to as ODSs. See ozone.), consistent with the schedules developed under the Montreal Protocol Exit. In stages, the U.S. phaseout has reduced the amount of ODS that may be legally produced or imported into the country. The Parties to the Montreal ProtocolMontreal 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 (http://ozone.unep.org/Publications/MP_Handbook/Section_1.1_The_Montreal_Protocol/) is available from the United Nations Environmental Programme (UNEP). have changed the phaseout schedule over time through adjustments and amendments. EPA has accelerated the phaseout in the United States under its Clean Air ActClean Air ActA law amended by Congress in 1990. Title VI of the CAA (http://www.epa.gov/ozone/title6/index.html) 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. authority.

In the United States, ODS are regulated as Class I or Class II controlled substances. Class I substances are primarily chlorofluorocarbons (CFCs). They have a higher ozone depletion potentialozone depletion potentialA 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 CFC-11. Thus, the ODP of CFC-11 is defined to be 1.0. Other CFCs and HCFCs have ODPs that range from 0.01 to 1.0. The halons have ODPs ranging up to 10. Carbon tetrachloride has an ODP of 1.2, and methyl chloroform's ODP is 0.11. HFCs have zero ODP because they do not contain chlorine. A table of all ozone-depleting substances (http://www.epa.gov/ozone/science/ods/index.html) shows their ODPs, GWPs, and CAS numbers. and have been completely phased out, except for limited exemptions allowed under the Montreal Protocol. Class II substances are hydrochlorofluorocarbonshydrochlorofluorocarbonsCompounds containing hydrogen, fluorine, chlorine, and carbon atoms. Although ozone depleting substances, they are less potent at destroying stratospheric ozone than chlorofluorocarbons (CFCs). They have been introduced as temporary replacements for CFCs and are also greenhouse gases. See ozone depleting substance. (HCFCs), which were transitional substitutes for many Class I substances. HCFCs are being phased out now.

• More information on the phaseout of Class I substances (CFCs)
• More information on the phaseout of Class II substances (HCFCs)