First Alert BRK 3120b-3 Hardwired Smoke Detector with Photoelectric and Ionization with Battery Backup, 3-Pack - Megean

Equipped with both a photoelectric and ionization sensor to quickly detect both fast burning, and smoldering fires, which alerts you with an 85-decibel alarm - Equipped with Optipath 360 technology that enhances detection with 360-degree access, and reliably detects smoke - To ensure complete protection make sure to place one on each level of your home and in each bedroom - Simple to use, with a single test/silence button and side-load battery compartment; included mounting bracket makes installation easy - Equipped with a dual photoelectric and ionization smoke sensor to quickly detect both fast-burning and smoldering fires