Freon is a registered trademark of The Chemours Company, which it uses for a number of halocarbon products. They are stable, nonflammable, moderately toxic gases or liquids which have typically been used as refrigerants and as aerosol propellants. These include the chlorofluorocarbons (CFCs) that cause ozone depletion (such as chlorodifluoromethane), but also include newer refrigerants which typically include fluorine instead of chlorine and do not deplete the ozone layer. Not all refrigerant is labelled as "Freon" since Freon is a brand name for the refrigerants R-12, R-13B1, R-22, R-502, and R-503 manufactured by The Chemours Company.
The first CFCs were synthesized by Frédéric Swarts in the 1890s. In the late 1920s, a research team was formed by Charles Franklin Kettering in General Motors to find a replacement for the dangerous refrigerants then in use, such as ammonia. The team was headed by Thomas Midgley, Jr. In 1928, they improved the synthesis of CFCs and demonstrated their usefulness for such a purpose and their stability and nontoxicity. Kettering patented a refrigerating apparatus to use the gas; this was issued to Frigidaire, a wholly owned subsidiary of General Motors. In 1930, General Motors and DuPont formed Kinetic Chemicals to produce Freon. Their product was dichlorodifluoromethane and is now designated "Freon-12", "R-12", or "CFC-12". The number after the R is a refrigerant class number developed by DuPont to systematically identify single halogenated hydrocarbons, as well as other refrigerants besides halocarbons.
Most uses of CFCs are now banned or severely restricted by the Montreal Protocol, as they have been shown to be responsible for ozone depletion. Brands of Freon containing hydrofluorocarbons (HFCs) instead have replaced many uses, but they, too, are under strict control under the Kyoto protocol, as they are deemed "super-greenhouse effect" gases. They are no longer used in aerosols, but to date no suitable, general use alternatives to the halocarbons have been found for refrigeration that are not flammable or toxic, problems the original Freon was devised to avoid.
According to their material safety data sheets, CFCs and HCFCs are colourless, volatile, toxic liquids and gases with a faintly sweet ethereal odour. Overexposure at concentrations of 11% or more may cause dizziness, loss of concentration, central nervous system depression, and/or cardiac arrhythmia. Vapors displace air and can cause asphyxiation in confined spaces. Although non-flammable, their combustion products include hydrofluoric acid and related compounds.
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