We show here that a palladium capped samarium film at room temperature can be used as an efficient sensor material for hydrogen detection. As low as 194 ppm of hydrogen gas can be detected without any cross sensitivity problem. Depending upon the partial pressure of hydrogen, response times varying from 6 to 30 s have been obtained. An interesting observation is very fast hydrogen desorption (2 s) at room temperature, thus making the sensing element ready for reuse quickly. No external source is needed with this sensor element.