Chlorofluorocarbons (CFCs) have been widely used
as refrigerants in refrigerators and air conditioners, and
as aerosols, foaming agents, etc. Since the 1970s, their
high potential for depletion of the ozone layer in the
stratosphere has been pointed out (Molina and Rowland,
1974) and the production of specified CFCs has been
discontinued since 1995. Recently, hydrochlorofluorocarbons
(HCFCs) have mainly been used as substitutes
for CFCs. In particular, a large amount of HCFC-22
(CHClF2) is used as a substitute for CFC-12 (CCl2F2)
as the refrigerant in refrigerators and air conditioners.
However, HCFCs also have high ozone-depletion potential,
although not as high as CFCs, and it is planned to
replace HCFCs with HFCs, which have no ozone-