Carbon Monoxide (CO) is a colorless and odorless gas produced by incomplete combustion that is lethal at high concentrations. In the home CO can be formed, for example, by open flames, space heaters, water heaters, blocked chimneys or running a car inside a garage. A carbon monoxide detector or CO detector is a device that detects the presence of the carbon monoxide (CO) in order to prevent carbon monoxide poisoning . If a high concentration of CO is detected, the device sounds an alarm, giving people in the area a chance to ventilate the area or safely leave the building. CO detectors do not serve as smoke detectors and vice versa. However, dual smoke/CO detectors are also sold. Smoke detectors detect the smoke generated by flaming or smoldering fires, whereas CO detectors can alarm people about faulty fuel burning devices.