Aprotonic polymer electrolyte based on polybenzimidazole is proposed for use in a hydrogen sensor, operating at room temperature, in air. The potentiometric response in inert gas containing hydrogen obeys the Nernst equation. In air, the EMF is a mixed potential which results from the hydrogen oxidation and the oxygen reduction. The response time is of the order of 30 s whatever the hydrogen concentration step within the hydrogen partial pressure range from 10(-3) to 1 atm.