Transportation of hydrogen is one of the greatest hurdles to overcome in the development of a clean hydrogen economy [1]. A cost-effective solution to transportation of hydrogen is to mix it with natural gas (NG) and utilize current pipeline infrastructure for transportation [2]. However, hydrogen embrittlement, the higher diffusivity of H2, and the uncertain state of much of existing infrastructure makes leaks of H2 an environmental and safety concern. Current NG leak detection technologies largely use optical sensors such as IR spectrometers that are incapable of detecting H2 gas [3]. Mixed potential electrochemical sensors (MPES) are low-cost, robust devices capable of detecting a wide variety of gases [4], with the sensitivity and selectivity necessary for point source monitoring of natural gas leaks [5].Multi-electrode MPES devices using Indium Tin Oxide, Au, and La0.87Sr0.13CrO3 and Pt electrodes have previously successfully quantified CH4 in natural gas at the 10-40 ppm level [5]. In this work, we demonstrated that the Au vs. Pt electrode has a low limit of detection of < 3 ppm for H2 in an air atmosphere. We also performed field testing of H2 emissions at CSU’s Methane Emissions Technology Evaluation Center (METEC) in both underground and above-ground emissions of H2 and H2 + natural gas mixes (Figure 1) with successful detection of H2 at the ppm level. Finally, we evaluate the stability of the selectivity and sensitivity during prolonged exposure to H2 and CH4.This work was supported by US Department of Energy Award DE-FE0031864.