Long-distance free space gas detection system based on QEPTS technique for CH4 leakage monitoring

• A long-distance free space QEPTS gas detection system is proposed. • An integral MDL of 3.79 ppb·m is achieved at 502 s integration time. • The system has a good ability to monitor CH 4 leakage. Based on the quartz tuning fork enhanced photothermal spectroscopy (QEPTS) technology, a long-distance free space gas detection system was proposed to monitor CH 4 leakage. A CH 4 absorption line at 1650.961 nm was selected for this gas detection system to reduce the interference of water vapor and carbon dioxide in the atmosphere. The Allan deviation analysis showed that the integral detection limit of this long-distance free space gas detection system for CH 4 detection could reach 3.79 ppb·m at the optimal integration time of 502 s. And the linear response of the proposed sensor was evaluated, with yielded R-square value of 0.997 being obtained. In addition, a CH 4 cylinder with concentrations of 5% was placed in different positions to simulate the leakage of CH 4 in free space, and the experimental results showed that the long-distance free space with a QEPTS gas detection system could meet the need for CH 4 leakage detection in the practical engineering application.