First Alert, 10 Year, Photoelectric Micro Smoke Alarm, Provides Early Warning Of A Fire, A Fully Insect Screened Photoelectric Smoke Sensing Chamber, An 85 Db Horn, A Sealed 10 Year Lithium Power Cell Power Supply That Is Permanently Installed, A Full Function Test Switch, A Silence Feature To Silence Unwanted Nuisance Alarms, An LED Light That Indicates DC Power Or Alarm, Tamperproof Design Will Not Allow The Powercell To Be Removed, Low Power Warning Indicator Will Cause The Alarm To Chirp When It Reaches The End Of Its Service Life & Needs To Be Replaced, Upon End Of Life, The Unit Meets UL Requirements For Disabling The Alarm & Non-Reinstallation Of Unit To Mounting Bracket, Designed For Wall Or Ceiling Mounting, Includes Mounting Anchors & Screws.