First Alert BRK SC9120B-12 Hardwired Smoke and Carbon Monoxide (CO) Detector with Battery Backup, 12-PackThe First Alert SC9120B Hardwired Combination Ionization Smoke and Carbon Monoxide Alarm with Battery Backup delivers both smoke and carbon monoxide detection in a single unit. This 120-volt AC smoke detector uses an ionization smoke sensor to reliably detect smoke from hot, fast-flaming fires. It also features an advanced electrochemical sensor that detects carbon monoxide leaks from multiple sources such as faulty fuel-burning appliances and blocked chimneys. If a threat is detected, the alarm sounds a loud siren that helps alert you to danger. Designed to be hardwired directly into the electrical system of your home or facility, this 120-volt hardwired smoke detector features a backup battery that helps keep the alarm functioning even in the event of a power outage. A universal mounting bracket makes installation easy and helps hide drywall cutouts, while tamper-resistant locking pins keep the alarm secure. And thanks to the convenient test/silence button, you can easily check whether the alarm is functioning properly and mute false alarms. This smoke and carbon monoxide alarm can integrate with up to 12 other First Alert or BRK hardwired alarms and features a latching indicator that identifies which unit triggered the alarm. Ideal for coverage of larger areas, this pack of 12 alarms can help you protect your entire home or facility from carbon monoxide leaks and fires.First Alert 9120B Smoke Detector, Hardwired Alarm with Battery Backup, 6-PackThis 6 pack of First Alert hardwired smoke alarms includes a 9 volt battery backup that continues to protect you in the event of a power failure. The detector features an ionization sensor for detection of smoke and fast flaming fires, as well as a loud, 85 decibel alarm. One button silences any nuisance alarms, and also tests detector functions, while lights indicate if the alarm detects smoke. The latching alarm indicator automatically identifies which unit initiated the alarm, even after the conditions that set off the alarm have subsided. And an end of life signal enhances your safety by letting you know when it's time to replace the unit. Connect it to compatible BRK or First Alert alarms within a single family residence. When one alarm is triggered, all connected alarms will sound.NOTE:The product is a hardwired alarm, also confirm if the wiring polarity is correct and that all wire nut connections are secure. A loose neutral (white wire) connection within the home junction box could prompt a device malfunction. First Alert 120 Volt Wire-In with Battery Backup smoke alarm in 6 pack contractor pack