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. People do not often take note of these small circular devices attached to the ceiling or square ones on the wall. These are devices that you probably have not touched at all, except when you needed to change the batteries. Or when you needed to check whether it was working or not. Whether you know what they are therefor or not, smoke detectors are actually life savers. They are usually connected to a fire alarm that sets off an audible warning when triggered, or to the automatic sprinkler system if you happen to have one installed in your house. In countless instances, smoke detectors have given ample time for home or office occupants to escape before the fires could do greater damage. They have certainly saved lives. Having a smoke detector warns a house occupant early on that something is burning and needs to be put out.