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