Hydrogen is considered crucial in the replacement of today’s fossil-based energy infrastructure. However, the production by water electrolysis poses some concerns, namely gas crossover, which has been reported as lowering the Faraday efficiency and presenting a safety risk. Hence, there is a demand for quantification and detection of this phenomena. In this study, semiconductor and potentiometric sensors have been utilized, and have been evaluated for their reliability pertaining to detecting hydrogen gas crossover. In situ measurements were performed for both sensor types, with varying the parameters temperature, oxygen gas concentration and hydrogen gas concentration. The semiconductor sensor used was Figaro TGS-2611 wired to an Arduino microcontroller for measurements of the resistance. The potentiometric sensor utilized was based on a fuel cell, and its open circuit potential was measured. After its calibrations, the potentiometric sensor was connected in-line with an anion exchange membrane water electrolyzer (AEM-WE) constructed with a Versogen’s PiperION® membrane. It is shown that semiconductor gas sensors are unreliable in high oxygen gas concentrations and could not detect changes in hydrogen gas concentration in this environment. On the contrary, the potentiometric sensor detected slight variations in hydrogen gas concentration even amidst high oxygen gas concentration, but the resolution was sensitive to relative humidity. Future aspects to improve regarding the sensors are its sensitivity to changes in relative humidity and oxygen gas concentration, signal-to-noise ratio and cost.