Characterization of H(2)S QEPAS detection in methane-based gas leaks dispersed into environment.

The increase in fatal accidents and chronic illnesses caused by hydrogen sulfide (HS) exposure occurring in various workplaces is pushing the development of sensing systems for continuous and in-field monitoring of this hazardous gas. We report here on the design and realization of a Near-IR quartz-enhanced photoacoustic sensor (QEPAS) for HS leaks detection. HS QEPAS signal was measured in matrixes containing up to 1 % of methane (CH) and nitrogen (N) which were chosen as the laboratory model environment for leakages from oil and gas wells or various industrial processes where HS and CH can leak simultaneously. An investigation of the influence of CH on HS relaxation and photoacoustic generation was proposed in this work and the sensor performances were carefully assessed with respect to CH content in the mixture. We demonstrated the high selectivity, with no cross talk between HS, HO and CH absorption lines, high sensitivity, and fast response time of the developed sensor, achieving a minimum detection limit (MDL) of 2.5 ppm for HS with 2 s lock-in integration time. The employed 2.6 µm laser allowed us to employ the sensor also for CH detection, achieving an MDL of 85 ppm. The realized QEPAS sensor lends itself to the development of a portable and compact device for industrial monitoring.