The Kidde KN-COB-DP2 plug-in carbon monoxide alarm with battery backup provides you and your family with a warning signal to protect against dangerous levels of carbon monoxide in your home. The battery backup feature provides continuous monitoring of CO levels, even during power outages when AC-only units are not providing protection. The KN-COB-DP2 alarm has a 10-year product life, providing 40% longer protection than other CO alarms.