Tunable diode laser absorption spectroscopy for open-path monitoring gas markers in fire combustion products

Abstract

This paper presents an open-path gas sensing technique based on tunable diode laser absorption spectroscopy (TDLAS) for simultaneously detecting multiple gas markers in fire combustion products for the purpose of early warning of fires. To demonstrate this detection method, a dual-gas sensing system was developed by combing calibration-free direct absorption spectroscopy (DAS) and a homemade three-mirror multi-pass optical system. A near-infrared (NIR) distributed feedback (DFB) diode laser emitting near 1579 nm was used as an excitation light source for simultaneously measuring dual-gas fingerprint absorption spectra of CO and CO2 in combustion products. Details of laser tuning characteristics, the cross-talk effect of CO and CO2 absorption spectra, and concentration response characteristics are initially investigated both theoretically and experimentally. Finally, various coal samples (anthracites) are used for evaluating the developed dual-gas sensor’s real-time response and combustion characteristics. The experimental results are in good agreement with the theoretical expectation, which proves its great potential for early diagnosis and warning research of fires and practical engineering applications.