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.