Hydrogen safety sensors must meet specific performance requirements, mandated by the U.S. Department of Energy, for hydrogen fueling station monitoring. Here, we describe the long-term performance of two zirconia-based mixed potential electrochemical hydrogen gas sensors, developed specifically with a high sensitivity to hydrogen, low cross-sensitivity, chemical stability across operating temperatures, and fast response time. Over a two-year period, sensors with two different working electrodes-tin-doped indium oxide and strontium doped lanthanum chromite-were deployed at hydrogen filling stations in the Los Angeles area. The sensors exhibit high baseline stability and excellent correlation with logged filling/release events, making these materials good candidates for applications requiring long-life, drift-free baseline operation, in which sensor calibrations and replacements are prohibitive.