The fast response characteristics of a Pt-FET hydrogen sensor have been investigated using a hydrogen gas flow system and a flow-through cell for the sensor. The Pt-FET hydrogen sensor showed good linear response, detecting hydrogen concentrations from 10 ppm to 10%, and had a sensitivity of -25.1 mV/decade at room temperature, which is close to the value for the Nemstian slope. The transient response characteristic shows that the equivalent catalytic reaction on the platinum surface is dominant in the response time. (c) 2005 Elsevier B.V. All rights reserved.