Reliable hydrogen sensors are essential to detect accidental hydrogen releases when hydrogen will be used to fuel future vehicles. To assess the performance of hydrogen safety sensors under conditions typical of automotive applications a test protocol has been defined. It has been experimentally evaluated by performing tests on commercially available hydrogen sensors. Catalytic sensors measured hydrogen concentration accurately and sensor response was largely independent of ambient parameters. However they were significantly cross sensitive to carbon monoxide and the detection limit was high. metal-oxide semiconductive sensors had a low detection limit and showed a low cross sensitivity to carbon monoxide however almost all of these samples showed poor accuracy and a strong dependence on ambient parameters. Electrochemical sensors also had a low detection limit however ambient parameters, cross sensitivity and accuracy tests showed a high variation in results. Tests on a limited number of thermal conductivity sensors highlighted their high detection limit and strong dependence on temperature. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.