Kidde KN-COB-B-LP Nighthawk Carbon Monoxide Alarm, Battery Operated - 21007268 Battery operated (three AAs included) to provide protection during power outages Test-reset button tests the unit for proper operation and resets the carbon monoxide alarm Forty percent longer life than other CO alarms Seven-year end-of-life warning alerts user to replace CO alarm Meets the requirements of Underwriters Laboratories (UL)