First Alert SA303CN3 Battery Powered Smoke Alarm with Silence Button Help keep your family safe with this battery-powered smoke alarm featuring an ionization sensor for smoke detection; a loud 85-decibel alarm sounds when smoke levels are elevated Ionization sensor is effective in recognizing smoke from flaming fires such as paper and grease fires Battery-operated alarm unit provides continuous monitoring even if there's a power failure; plus, it's easy to install Tamper-resistant alarm also features a single test/silence button, side battery door, and missing-battery guard To ensure complete protection make sure to place one on each level of your home and in each bedroom