The First Alert PRC710 Slim Photoelectric Smoke and Carbon Monoxide Combo Alarm with 10-Year Battery helps protect your home from 2 potentially deadly threats by providing up to a decade of uninterrupted monitoring. Equipped with dual sensors this low-profile alarm detects smoke from slow-burning smoldering fires and elevated carbon monoxide levels. This detector has a slim contemporary design that mounts unobtrusively on a wall or ceiling. A built-in 10-year Li-Ion battery provides continuous power with no need to ever worry about changing the battery during the lifetime of the alarm.