First Alert 9V Battery Operated Smoke Alarm with Escape Light, Comes Equipped With A Bright Light To Illuminate A Clear Path To Assist Owners In Their Escape, Utilizing An Ionization Smoke Sensor, This Alarm Performs Exceptionally Well In Detecting Smoke Brought On By Flaming Fires, A Mute Button Has Been Included To Serve The Dual Purpose Of Silencing Nuisance Alarms & Testing The Functionality Of Your Alarm, EZ Access Battery Door Removes The Hassles & Burdens Associated With Changing Your Alarm's Batteries, Further Additions Such As A Theft Prevention Lock Establish Peace Of Mind & Eliminate The Thought Of Others Tinkering With Your Alarm, Meets UL217 Standards, 10 Year Limited Warranty.