Kidde Intelligent Alarm Battery Operated Combination Smoke & Carbon Monoxide Alarm offers a fast response to real fires, including smoldering and fast-flaming, as well as protect you from carbon monoxide and dramatically reduce the chance of nuisance alarms. The Intelligent Alarm combines the detection capabilities of an ionization smoke sensor - which is more likely to detect smaller, less visible fire particles, like those produced by flaming fires - with that of an electrochemical sensor, which is used to detect CO.