Patent ID: 7329389

Claim:
A sensor for detecting gas phase substances, comprising: a) a sensing element in contact with the gas phase substances, comprising: a first supporting substrate, a first heater attached to the first supporting substrate, a first temperature detector in thermal contact with the first heater, and a catalyst in thermal contact with the first temperature detector and the first heater, wherein the catalyst interacts with the gas phase substances, and wherein the interaction comprises one of endothermic and exothermic heat flow from the catalyst to the first temperature detector; b) a reference element in contact with the gas phase substances, comprising; a second supporting substrate, a second heater attached to the second supporting substrate, a second temperature detector in thermal contact with the second heater; and c) a thermal barrier separating the sensing element from the reference element, and d) a heat flow monitor connected to both the sensing and reference elements for measuring any change in heat flow between the sensing element relative to the reference element.