Laser-Based Monitoring of CH(4), CO(2), NH(3), and H(2)S in Animal Farming—System Characterization and Initial Demonstration

In this paper, we present a system for sequential detection of multiple gases using laser-based wavelength modulation spectroscopy (WMS) method combined with a Herriot-type multi-pass cell. Concentration of hydrogen sulfide (H(2)S), methane (CH(4)), carbon dioxide (CO(2)), and ammonia (NH(3)) are retrieved using three distributed feedback laser diodes operating at 1574.5 nm (H(2)S and CO(2)), 1651 nm (CH(4)), and 1531 nm (NH(3)). Careful adjustment of system parameters allows for H(2)S sensing at single parts-per-million by volume (ppmv) level with strongly reduced interference from adjacent CO(2) transitions even at atmospheric pressure. System characterization in laboratory conditions is presented and the results from initial tests in real-world application are demonstrated.