Phaseout of Class II Ozone-Depleting Substances

“Class II” ozone-depleting substances ( ODS ozone-depleting substance (ODS) A 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 is available. ) have an  ozone depletion potential ozone depletion potential 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 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 detailed list of class I and class II substances with their ODPs, GWPs, and CAS numbers is available.  less than 0.2, and are all hydrochlorofluorocarbonshydrochlorofluorocarbonsA compound consisting of hydrogen, chlorine, fluorine, and carbon. The HCFCs are one class of chemicals being used to replace the 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 with the highest ODPs are being phased out first, followed by other HCFCs. A detailed list of class I and class II substances with their ODPs, GWPs, and CAS numbers is available. (HCFCs). HCFCs were developed as transitional substitutes for Class I ODS and are subject to a later phaseout schedule than Class I ODS.

As a Party 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 is available from the United Nations Environmental Programme (UNEP)., the United States must incrementally decrease HCFC consumption and production, culminating in a complete HCFC phaseout in 2030. HCFC usage must be reduced to at least 90 percent below baseline levels in 2015 and to at least 99.5 percent below baseline levels in 2020.

Section 605 of the Clean Air ActClean Air ActA law amended by Congress in 1990. Title VI of the CAA 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. establishes the U.S. phaseout targets for Class II substances. In 1993, EPA established the phaseout framework and the "worst-first" approach, which focused first on HCFC-22, HCFC-141b, and HCFC-142b because they have the highest ozone depletion potentials of all HCFCs.