FREON

(trademark), any of several chlorofluorocarbons (CFCs) that are used in commerce and industry. The CFCs are a group of aliphatic organic compounds containing the elements carbon and fluorine and, in many cases, other halogens (especially chlorine) and hydrogen. The name Freon is a trademark registered by the E.I. du Pont de Nemours & Company. The Freons are colourless, odourless, nonflammable, noncorrosive gases or liquids of low toxicity that were introduced as refrigerants in the 1930s; they also proved useful as propellants for aerosols and in numerous technical applications. Their low boiling points, low surface tension, and low viscosity make them especially useful refrigerants. The presence of fluorine atoms in Freon molecules makes them extremely stable, inert compounds that are entirely harmless to humans. The Freons neither present a fire hazard nor give off a detectable odour in their circulation through refrigerating and air-conditioning systems. The most important members of the group have been dichlorodifluoromethane (Freon 12), trichlorofluoromethane (Freon 11), chlorodifluoromethane (Freon 22), dichlorotetrafluoroethane (Freon 114), and trichlorotrifluoroethane (Freon 113). In the mid-1970s it was suggested that Freons and other CFCs were, by chemical reaction, destroying the ozone present in the stratosphere. Depletion of the ozone could create a threat to animal life on the Earth because ozone absorbs ultraviolet radiation that can induce skin cancer. The use of Freons in aerosol-spray containers was banned in the United States in the late 1970s. By the early 1990s, accumulating evidence of ozone depletion in the polar regions had heightened worldwide public alarm over the problem, and in 1992 most of the developed nations agreed to end their production of Freons and other CFCs by 1996. See also chlorofluorocarbon.