First Alert Carbon Monoxide Alarm, Plug-In w/Battery Backup

Ac/dc, plug in, dual power carbon monoxide alarm, alerts you to dangerous carbon monoxide, dual power system with battery back up for continuous monitoring, even in the event of a power outage, the backlit digital screen tells you at a glance what the carbon monoxide & power levels are, features a convenient test & silence button & an end of life timer that lets you know when it is time to replace the unit, electrochemical sensor type.