Abstract: A dual carbon monoxide detection system is provided including a gas furnace having a heat exchanger with a supply air duct for delivering heated air and a return air duct for receiving air to be heated. The gas furnace further has a gas input line for receiving gas from a gas supply line for heating purposes. A first carbon monoxide detector is situated within the supply air duct for generating an activation signal upon the detection of more than a predetermined amount of carbon monoxide. Associated therewith is a second carbon monoxide detector situated within the return air duct for generating the activation signal upon the detection of more than a predetermined amount of carbon monoxide. A gas valve is coupled between the gas input line and the gas supply line. The gas valve is adapted to preclude the flow of gas through the gas input line only upon the receipt of power. Connected to the gas valve is a relay for delivering power thereto upon the receipt of the activation signal.