The Kidde Smart Smoke & Carbon Monoxide Detector & Indoor Air Quality Monitor, WiFi, Alexa Compatible Device, Hardwired w/Battery Backup, Voice & App Alerts, model P4010ACSCOAQ-WF, uses photoelectric sensor technology to detect visible fire particles, associated with smoldering fires, & electrochemical sensor to detect carbon monoxide. The Kidde smart combination alarm alerts you by sounding an 85-decibel alarm with a voice alert announcing "Fire! Fire!" or "Warning! Carbon Monoxide!". The Kidde smart combination alarm connects to your home's wiring using standard 120V AC power voltage & provides battery backup in the event of a power failure. The built-in lithium battery backup lasts the full 10-year life of the alarm, so you'll never have to replace a battery. Real-time notifications are provided through the Kidde app, so your family & friends - even the pet sitter - can monitor your home's air quality & receive alerts to smoke or CO presence, high humidity levels that can lead to mold or Total Volatile Organic Compounds (TVOCs). Setup is easy: simply download the Kidde app, and scan the QR code at the back of the combination alarm. You can also use voice commands to check the connection & status of your detector 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, fire, or CO 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).Capable of hardwired interconnection to other select Kidde alarms for whole-home activation – when one alarm sounds, they all do**. UL Listed with a 10-Year limited manufacturer warranty on the alarm only (not a battery performance claim). Warranty begins when the alarm is powered on. If that date is unknown, it should be assumed that replacement is needed. **Alarms only connect with select Kidde alarms that have hardwired AC interconnect capability (see User Guide).