Battery Operated, Carbon Monoxide Alarm, With Digital Display, Easy To Use, Protects Your Family, Detects The Carbon Monoxide You Can't See, Smell Or Taste In The Air, Alarm Uses An Electrochemical Carbon Monoxide Sensor, Easy To Read Back Lit Digital LED Display Communicates A Clear Read Out Of Current Carbon Monoxide Concentrations In Parts Per Million, Battery Back Up Gives You Peace Of Mind During Power Outages, Test/Silence Button Both Silences A Non-Threatening Alarm & Low Battery Warning & Allows You To Test The Unit's Functionality, Comes With 1 Carbon Monoxide Alarm, A User's Manual, & "AA" Batteries.