The FIRST ALERT CO615 dualpower carbon monoxide plugin alarm alerts you to dangerous carbon monoxide This carbon monoxide detector operates on a dualpower 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 CO monitor also features a convenient test and silence button and an endoflife timer that lets you know when it is time to replace the unit Digital Display, 85 dB