Infrared fiber optic gas sensor for chlorofluorohydrocarbons

In this paper the detection of several gaseous species of chlorofluorohydrocarbons such as 1,2-dichlorotetrafluoroethane (R 114) or trifluoromethane (R 23) using the fiber optic evanescent field absorption spectroscopy is presented. By coupling mid-infrared transparent silver halide fibers to a conventional Fourier transform infrared spectrometer reasonable results could be obtained in the concentration range of 1–15% of the gas species diluted in synthetic air using a gas sensing device exploiting uncoated fibers. As shown for the example R 114 the enrichment of the analyte in a polymer layer (low-density polyethylene, polyisobutylene) coating the fiber lowered the detection limit to 0.1%.