Patent ID: 8201992

Claim:
A sensor for detecting gas phase substances, comprising: a sensing element in contact with the gas phase substances, comprising: a first resistance temperature detector which functions as a temperature detector and a variable resistance heater, and a first catalyst in thermal contact with the first resistance temperature detector, wherein the first catalyst interacts with the gas phase substances; a reference element in contact with the gas phase substances, comprising: a second resistance temperature detector which functions as a temperature detector and a variable resistance heater, and a second catalyst in thermal contact with the second resistance temperature detector, wherein the second catalyst interacts with the gas phase substances; a thermal barrier separating the sensing element from the reference element; and a heat flow monitor connected to both the sensing and reference elements for measuring any change in heat flow for the sensing element relative to the reference element by monitoring the change in electric power needed to maintain the first resistance temperature detector at a desired temperature relative to the second resistance temperature detector.