First Alert Carbon Monoxide Plug-In Alarm with Battery Backup: * Easy to install * UL-listed * Features advanced technology, a user-friendly design, and backup battery * Comes with an "Alarm Action" chart that instructs you on what to do if the alarm sounds * Uses an electrochemical carbon monoxide sensor, the most accurate CO sensor available * If a high concentration of CO is detected, the unit will sound a clear, loud, 85-decibel alarm * Runs on A/C power * In case of electrical outage, unit switches to battery operation * Installation is a snap. CO605 plugs into any wall outlet, with no additional mounting * Features 2 "AA" batteries (included) for backup * Button clearly labeled "Test/Silence" lets you test the unit * Front-open compartment allows for easy battery changes without dismounting the alarm * End-of-life chirp lets you know when it"s time to replace the unit * 5-year limited warranty * Model# CO605-8CSD-8