The Environmental Sensors Team of the Synergy Materials Research Center, AIST, has developed a low cost, wide range hydrogen sensor. The sensor is based on the novel gas sensor device combining a thermoelectric conversion material with a platinum catalyst which was presented last year by the same team. At operating temperature of 60 to 100 ºC, the platinum catalyst selectively reacts with hydrogen gas, so the sensor has high selectivity to hydrogen gas. This new sensor is uniquely able to sense hydrogen concentrations from 250ppm to 10% in air, and is suitable for integration into silicon substrates.