First Alert #1039868 slim photoelectric smoke and carbon monoxide alarm with 10-year battery helps protect homes from two potentially deadly threats by providing up to a decade of uninterrupted monitoring. Equipped with dual sensors, detects smoke from slow-burning, smoldering fires. Half as thick as a standard alarm, features a slim, contemporary design that mounts unobtrusively on a wall or ceiling. Includes a built-in 10-year lithium-ion battery provides continuous power, with no need to ever worry about changing the battery during the lifetime of the alarm.