Compact TDLAS Sensor System for ppm-Level CO Detection in Early Electrical Fires Using a Low-Power Laser Diode and Miniature Multipass Cell

A compact tunable diode laser absorption spectroscopy (TDLAS) gas sensor system for ppm-level carbon monoxide (CO) detection is demonstrated, featuring a miniature multipass cell (MPC) gas sensor module with an effective optical path length of ~4.8 m to take advantage of the directly proportional relationship between sensitivity and gas absorption path length, thereby improving the detection sensitivity. A low-power distributed feedback (DFB) laser with a power output of 2.8 mW was used as the excitation light source to further reduce power consumption, size, and weight of the TDLAS gas sensor system. The sensor performance was optimized and evaluated in terms of modulation depth, pressure, gas flow rate, signal linearity, accuracy, and stability. A minimum detection limit of 1.7 ppm was achieved with a 1-s integration time, further improved to 0.12 ppm with a 208-s integration time. Real-time measurements of CO concentration released during the combustion of cigarettes, heat-shrink tubing, and cable sheaths were performed to demonstrate the practicality and feasibility of the reported CO sensor system in early electrical fires.