A small @R05088@ containing 3H or 63Ni ionizes the molecules of the @C00863@ (nitrogen or argon–methane), and a potential difference creates a small current. This current is reduced when an electronegative substance (such as a halocarbon) is introduced. The reduction in current is a measure of the concentration of the electronegative substance. The @D01628@ (threshold) varies greatly according to the substances to be analysed and can reach a mixing ratio of \(10^{-12}\). The linear dynamic range may be \(10^{4}\) but the maximum measuring value generally lies below \(1\ \text{ppmv}\).
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2191 [Terms] [Paper]