Using the KIDDE i4618 Hardwired Ionization Smoke Alarm with Battery Back Up Pack Of 4 you can get reliable smoke detection and peace of mind in your home. These smoke alarms are designed to be hardwired into your homes electrical system and feature a battery backup, so they will continue to monitor your home in the event of a power outage. The smoke alarm requires a 120-volt AC power source, and has a 9-volt battery backup that ensures continued function in the event of a power outage. With Kidde's Smart Hush feature, you can quickly silence the alarm.Each smoke alarm in this pack features ionization sensing technology that detects invisible fire particles sooner than photoelectric alarms. When an alarm occurs, a loud 85 decibel alarm will sound. This alarm is compatible with various home automation systems, including Amazon Alexa, Google Home, and Nest. With these features no one in your home is ever far from peace of mind.