In any application involving the production, storage or use of hydrogen, sensors are important devices for alerting to the presence of leaked hydrogen. Hydrogen sensors should be accurate, sensitive, and specific, as well as resistant to long term drift and varying environmental conditions. Furthermore, as an integral element in a safety system, sensor performance should not be compromised by operational parameters. For example, safety sensors may be required to operate at reduced oxygen levels relative to air. In this work we evaluate and compare a number of sensor technologies in terms of their ability to detect hydrogen under conditions of varying oxygen concentration.