Plug In, Carbon Monoxide Alarm, With Battery Back Up, Utilizes An Electrochemical Carbon Monoxide Sensor To Accurately Effectively Warn You Of Elevated Carbon Monoxide Levels, Can Be Continuously Monitored For Dangerous Carbon Monoxide Gas, Even During Power Outages, Simply Plug The Alarm Into A 120V Outlet Personal Carbon Monoxide Detector Is Ready To Go, When Carbon Monoxide Levels Rise Above A Safe Threshold, A Loud 85 Decibel Alarm Alerts You To The Threat, Designed For Simple Use, Has Just 1 Button That Silences Or Tests The Unit, As Well As An End Of Life Timer That Lets You Know When It Is Time To Replace The Device