Patent ID: 7418855

Claim:
A gas sensor comprising: a gas detection chamber into which a detection gas is introduced; a detecting element and a compensating element each disposed in the gas detection chamber and exposed to the detection gas; a first detection device which detects concentration of a detection target gas contained in the detection gas as a function of the difference in electrical resistance values between the detecting element and the compensating element; a dehumidifying element which is provided in the gas detection chamber, and reversibly absorbs water contained in the detection gas and drains off the water absorbed in the dehumidifying element; and a heater which changes the temperature of the dehumidifying element, wherein heating the dehumidifying element drains off the water absorbed in the dehumidifying element; wherein the dehumidifying element and the heater together prevent condensation within the gas detection chamber, and wherein the dehumidifying element includes a second dehumidifying member disposed on an inner wall of the gas detection chamber.