Taken from the Trane website
http://www.trane.com...ental/cfc6c.asp
CFC Refrigerants
Commercial chlorofluorocarbon (CFC) production began with R-12 in early 1931, R-11 in 1932, R-114 in 1933, and R-113 in 1934. The first hydrochlorofluorocarbon (HCFC) refrigerant, R-22, was produced in 1936.
By 1963, these five products accounted for 98% of the first total production of the organic fluorine industry. Annual sales had reached 372 million pounds, one-half of it R-12.[1] These chlorofluorochemicals were viewed as nearly nontoxic, nonflammable and highly stable, in addition to offering good thermodynamic properties and materials compatibility at a low cost.
Almost 50 years passed between the introduction of CFCs and recognition of their harm to the environment when released. Specific concerns relate to their depletion of stratospheric ozone and to possible global warming by their actions as greenhouse gases. Ironically, the high stability of CFCs enables them to deliver ozone-depleting chlorine to the stratosphere. The same stability prolongs their atmospheric lifetimes, and thus their persistence as greenhouse gases.