For the smoke detection the unit includes ionization sensing technology, which detects visible fire particles and warns of impending danger. The carbon monoxide alarm goes off if the carbon monoxide levels in your home increase to a dangerous level. The Kidde KN COSM B Battery Operated Combination Monoxide has four verbal warnings including fire, carbon monoxide, low battery and smart hush announcement. There is a voice alarm, a flashing light, along with a loud beeping sound that warns of danger. The Kidde KN COSM B Battery Operated Combination Monoxide alarm needs 3 AA batteries to operate and comes with a 5 year warranty. Smoke and Carbon Monoxide detectorIonization sensing fire technologyVoice warnings for fire, carbon monoxide, low battery and hushFlashing LED light and beeping warnings5 Year limited warranty– Anthony DawsonSmoke Detector Buying GuideYou do not have to experience any kind of fire or anything that causes excessive smoke in the house to understand how important smoke detectors are.