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Freeze 1995

Freeze 1995

Montreal protocol (September, 1987)

London amendment (June, 1990)

Copenhagen amendment (November, 1992)

Vienna amendment (November, 1995)

FIGURE 13.2 Summary of Montreal Protocol and subsequent amendments (adapted from Parson and Greene, 1995).

and, subsequently, for use as aerosol propellants and blowing agents. They were nontoxic, nonflammable, and highly stable. Of course, as described in the previous chapter, it is now known that it is these very properties that render them virtually nonreactive in the troposphere and hence give them sufficiently long lifetimes in the lower atmosphere to reach the stratosphere.

Table 13.1 shows the most common CFC substitutes currently in use. The physical and chemical properties that are needed for substitute compounds are described in an article by Manzer (1990) and the book edited by Miziolek and Tsang (1995). Overall, the approach in the short term has been to make these compounds more reactive in the troposphere by adding one or more abstractable hydrogens. The term "HCFC" is used for hydrochlorofluorocarbons, i.e., compounds containing hydrogen, chlorine, and fluorine, and "HFC"

TABLE 13.1 Some CFC Alternatesu

Name''

Compound

Use

HFC-134a

CH2FCF3

Automobile air conditioners, commercial chillers,

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