Portable Raman hydrogen concentration mapping with parts-per-billion sensitivity

A portable multipass cavity Raman gas analyzer is described, which uses the vibrational band of hydrogen as a concentration measure. Integrated into a Pelican case and combined with a desiccating gas handling system, it was tested inside a laboratory, within an atrium, and in an outdoor open space. The hydrogen concentration was measured as a function of time and distance from an electrolyzer producing up to 600 mL/min, with a total measurement duration under 5 min per sample at 0.34 MPa. The instrument was found to be capable of mapping excess hydrogen concentrations of 63 parts per billion (one standard deviation) above the ambient level from a distance of several meters away, even outdoors, enabling applications in leak detection and geological prospecting.