First Alert CO5120BN Hardwired Electrochemical Carbon Monoxide Alarm with Battery Backup. Includes a battery backup that is perfect for meeting codes wherever CO detectors are required for new construction. Features a quick plug-in power connector that makes the installation process a near effortless one as it will connect right into your building's wiring. Additional features such as a microprocessor that limits nuisance alarms and a single test/silence button add versatility to an already efficient carbon monoxide alarm. Includes an advanced electrochemical sensor that detects carbon monoxide leaks from a variety of sources, such as faulty fuel-burning appliances, blocked chimneys, and cars left running in the garage. The unit comes with a 9-volt battery and features a pivoting, easy-to-access battery drawer that allows you to replace the battery without dismounting the alarm. Can also integrate with up to 12 other First Alert or BRK hardwired alarms for coverage of larger spaces. It also integrates with up to six other compatible devices, such as bells, horns, and repeaters. If one alarm in the series is triggered, they will all sound. The alarm features a latching indicator to identify which unit triggered the alarm, alerting you to the area of danger.