ADLib Glossary (C)

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Ozone Depleting Substances

Chlorofluorocarbons (CFCs) - Definition

CFCs are a family of inert, nontoxic, and easily liquified chemicals used in refrigeration, air conditioning, packaging, insulation, or as solvents and aerosol propellants. At first they were thought to be harmless, due to their chemical inactivity but they are now known to be persistent in the upper atmosphere where they become active and destroy the ozone layer, they are also greenhouse gases. Until recently used extensively as aerosol propellants, solvents, refrigerants and in foam making. The signatories of the Montreal Protocol, set up under the auspices of the United Nations to control CFCs, have agreed to eliminate production of CFCs. Air conditioning and refrigeration equipment often contains CFCs or the related HCFCs.


The halons are used as fire extinguishing agents, both in built-in systems and in handheld portable fire extinguishers. They cause ozone depletion because they contain bromine. Bromine is many times more effective at destroying ozone than chlorine. Recent scientific studies indicate that the ozone depletion potentials of halon  are at least 12 and 6, respectively. Note: technically, all compounds containing carbon and fluorine and/or chlorine are halons, but in the context of the Clean Air Act, "halon" means a fire extinguishing agent as described above

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