The First Alert battery-operated smoke and carbon monoxide alarm features a photoelectric smoke sensor and an electrochemical carbon monoxide sensor. The photoelectric sensor detects larger smoke particles from smoldering fires from objects like cigarettes burning on furniture or in trash cans. The alarm features a loud, 85-decibel alarm, designed to wake even the soundest of sleepers. One button silences any nuisance alarms, and also tests detector functions, while lights indicate if the alarm detects smoke or carbon monoxide. The battery-operated smoke and CO detector can be installed easily, with no wires or electrician required, and its slim profile will seamlessly blend in with your home decor. The detector will continue monitoring during power outages, and its twist-lock mounting system makes replacing batteries easy. What's Included: Mounting Bracket with Hardware, User Manual, 9-volt BatteryKeep your family safe with this battery-operated smoke and carbon monoxide alarm; battery-operated means constant monitoring, even if there's a power failureFeatures electrochemical carbon monoxide sensing technology and photoelectric smoke sensor optimized to detect larger smoke particles produced by smoldering fires; helps minimize the number of false alarmsA loud 85-decibel alarm sounds when carbon monoxide, and smoke levels begin to riseFeatures a sleek, low-profile design to blend more fully into the wall and out of sight10-Year limited warranty; equipped with end-of-life signal chirp, so you know when it’s time to replace the unit for saferRigorously tested to meet UL standardsEasy-slide mounting bracket makes ceiling or wall installations a breezeAA battery included for long-lasting protection