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Definition: chlorofluorocarbon from Hawley's Condensed Chemical Dictionary

Any of several compounds composed of carbon, fluorine, chlorine, and hydrogen, the best known of which are trichlorofluoromethane and dichlorodifluoromethane. Their use was prohibited in 1979 except for a few specialized items because of their depleting effect on stratospheric ozone.

Summary Article: chlorofluorocarbon
From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide

A class of synthetic chemicals that are odourless, non-toxic, non-flammable, and chemically inert. The first CFC was synthesized in 1892, but no use was found for it until the 1920s. Their stability and apparently harmless properties made CFCs popular as propellants in aerosol cans, as refrigerants in refrigerators and air conditioners, as degreasing agents, and in the manufacture of foam packaging. They are now known to be partly responsible for the destruction of the ozone layer. In 1987, an international agreement called the Montréal Protocol was established; it was one of the first global environmental treaties and it banned the use of chemicals responsible for ozone damage, such as CFCs in aerosols and refrigerants.

When CFCs are released into the atmosphere, they drift up slowly into the stratosphere, where, under the influence of ultraviolet radiation from the Sun, they react with ozone (O3) to form free chlorine (Cl) atoms and molecular oxygen (O2), thereby destroying the ozone layer which protects the Earth's surface from the Sun's harmful ultraviolet rays. The chlorine liberated during ozone breakdown can react with still more ozone, making the CFCs particularly dangerous to the environment. CFCs can remain in the atmosphere for more than a hundred years. Replacements for CFCs are being developed, and research into safe methods for destroying existing CFCs is being carried out.

In 1998, the EU proposed a number of restrictions on CFCs and their production. They imposed a ban on maintaining machinery that still contained CFCs, a ban on production of equipment that used ‘safe’ hydrochlorofluorocarbons (HCFCs) other than in specific exemptions, leading to a total ban in 2007.

Under the terms of the Montréal Protocol, the production of ozone-depleting substances such as CFCs was banned in industrial countries in 1996, while developing countries were allowed to continue to produce them until 2010.


Ozone: Thinning of the Ozone Layer


greenhouse effect

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