ABSTRACT
This chapter presents a remote gas-sensing system with an operation band between 200 GHz and 500 GHz, developed for detecting toxic gases at the scene of a fire. The system employs a photonic terahertz wave generator and a superconductor-insulator-superconductor tunneling mixer, which provides both fast frequency sweeping and high receiver sensitivity at the same time. In a performance test of the system with a full-scale simulated fire, we succeeded in detecting hydrogen cyanide (HCN), which is produced by incomplete
combustion of urethane. The coincidence of the HCN concentration obtained from the developed system with the result of chemical analysis of a sampled gas demonstrates the potential of the system for use as a remote toxic gas sensor at disaster sites.
