Stratospheric acidic chlorine vapors were sampled up to 36 km by means of base-impregnated filters. The results do not reveal a measurable seasonal variability. The composite curve indicates a maximum of 0.8 ppbv at 24 km, decreasing to a minimum of 0.5 ppbv at about 31 km. The concentration then increases with altitude to 1.0 ppbv at 36 km.

Laboratory simulation tests yield collection efficiencies of 80% or more for chlorine nitrate, and 100% for hydrochloric acid vapor. However, the concentration of acidic chlorine agrees well with spectrometrically determined concentrations of hydrochloric acid at 25 km and below. This suggests that large concentrations of chlorine nitrate are not present, though photochemical models predict similar concentrations for both chlorine nitrate and hydrochloric acid vapor at 25 km.