Hydrogen purity sensor cells were newly developed with the principle of PEFC. By using the phenomena of PEFC's voltage drop seen in the presence of impurities and further minimizing the amount of Pt to make the cells more sensitive to impurities, the sensor cells were prepared. This unique sensing principle was applied to typical impurities in practical hydrogen gases, including CO, H2S, and NH3. Sensor responses were derived by analyzing various kinds of dependency on Pt loading, current density, impurity concentration, and operational temperature. Possibility of recovery from impurity poisoning was also studied by varying impurities' supply and potential charge. Consequently, our simple PEFC-type hydrogen purity sensors were verified to have ability to sense ppm-level impurities within 10 min. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.