The First Alert CO615 Dual-Power Carbon Monoxide Plug-in Alarm alerts you to dangerous carbon monoxide levels. This carbon monoxide detector operates on a dual-power system with battery backup for continuous monitoring even in the event of a power outage. The backlit digital screen tells you at a glance what the carbon monoxide and power levels are. The monitor also features a convenient test and silence button and an end-of-life timer that lets you know when it is time to replace the unit.