The Kidde Smart Smoke Detector, WiFi, Alexa Compatible Device, Hardwired with Battery Backup, Voice & App Alerts Value Pack, models P4010ACS-WF, uses photoelectric sensor technology to detect visible fire particles, associated with smoldering fires, and alerts you by sounding an 85-decibel alarm with voice alert announcing "Fire! Fire!". The Kidde smart hardwired smoke alarm connects to your home's wiring using standard 120V AC power voltage and provides battery backup in the event of a power failure. The lithium battery backup lasts the 10-year life of the alarm, so you'll have the benefit of never having to replace a battery. Update-to-date, real-time notifications are provided through the Kidde app, so your family & friends - even the pet sitter - can monitor your home's air quality & received alerts to smoke presence, high humidity levels that can lead to mold, unexpected high or low temperatures, or Total Volatile Organic Compounds (TVOCs). Setup is easy: simply download the Kidde app and scan the QR code at the back of the smoke alarm. You can also use voice commands to check the connection & status of carbon monoxide or air quality by pairing it with your Amazon Alexa, Google Home, and select iPhone & Android smart devices. The LED ring-light indicator alerts you to the unit's operational status: red = a smoke or fire hazard, amber = operating error, and green = normal operation. The Test-Hush button silences temporary nuisance alarms, tests if the unit is operating properly, and silences a low battery or end-of-life chirp (up to 24 hours at a time for a maximum of 7 days). Install a smoke detector on each level of your home and inside and outside each bedroom. The Kidde smoke detector is capable of hardwired interconnection to other select Kidde alarms for whole-home activation – when one alarm sounds, they all do**. UL Certified with a 10-year limited warranty (not a battery performance claim).