Careful measurements by GC/MS techniques on atmospheric carbon tetrafluoride confirm that itsconcentration in 1979 was constant at about 69.9 pptv (standard deviation is 7.2 pptv). It is almost certainly produced entirely by emissions from the aluminium industry. Other compounds in the atmosphere containing the CF3 group have been identified by GC/MS as C2F6, CF3CI, CF3Br, and C2FsCI. The concentrations of the first pair are about 4 pptv, and the latter two are about 0.7 pptv and 4 pptv, respectively. The C:F6 is produced simultaneously with CF4 in the manufacture of aluminium. CF3C1, CF3Br, and CeFsCI are probably produced by the chemical industry. The environmental importance of these compounds is discussed in the context of two papers on CF4 recently published by Cicerone (1979) and by Wang ½t al. (1980). power of the GC/MS combination to detect, identify, and strip chart recorder. quantify the concentration of low-level trace gases in the at-Because of the low boiling points of many of the commosphere. Information is also presented concerning the pos-pounds being measured and the likelihood of evaporation sible sources of these compounds.during the concentration procedure, the cryotrap efficiencies for CF4, C:F6, and CF3C1 were measured using standards. In

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Recent global measurements of CHClF2 (F‐22) are reported. Originally, GC/MS techniques were used to obtain these data. Since then, significant advances using an O2‐doped electron capture detector have been made in the analytical techniques, so that F‐22 can be measured by EC/GC methods at ambient concentrations. The atmospheric burden of F‐22 calculated from these measurements (average mixing ratio, mid‐1979, ∼45 pptv) is considerably greater than that expected from the estimates of direct industrial emissions (average mixing ratio, mid‐1979, ∼30 pptv). This difference is probably due to underestimates of F‐22 emissions.

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