Methyl chloride atmospheric lifetime

Table 1 lA presents tabulations of the safety of important refrigerants, but this list does not include aU available refrigerants. Table 11-5 summarizes a limited list of comparative hazards to life of refrigerant gas and vapor. The current more applicable refrigerants from the m or manufacturers of the CFC and HCFC refrigerants and their azeotropes/ blends/mrxtures are included, but the list excludes the pure hydrocarbons such as propane, chlorinated hydrocarbons such as methyl chloride and others, inorganics, ammonia, carbon dioxide, etc. See Table 11-6. The CFC compounds have a longer and more serious ozone depletion potential than the HCFC compounds, because these decompose at a much lower atmospheric level and have relatively short atmospheric lifetimes therefore, they do less damage to the ozone layer. Table 11-7 summarizes alternate refrigerants of the same classes as discussed previously. Table 11-8 correlates DuPont s SUVA refrigerant numbers to the corresponding ASHRAE numbers.

Methyl chloride reacts with OH radicals by hydrogen abstraction in the same way as methane, except that the rate coefficient is about five times greater. From the known rate coefficient and the usual assumption of an average OH number density of 5 x 105 molecules/cm3 in the troposphere, one infers an atmospheric lifetime for CH3C1 of about 1.8 yr. The uniform distribution of methyl chloride in the troposphere would be incompatible with such a relatively short lifetime, if the substance were mainly human-... 

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