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First Alert BRK SC9120B-3 Hardwired Smoke and Carbon Monoxide (CO) Detector with Battery Backup: Great for overhead drilling or hard-to-reach applications. Rigid shaft construction ensures straight, precise drilling. Black oxide coating resists corrosion.


  • Keep your family safe with this 3-pack of hardwired smoke and carbon monoxide alarm. The battery backup means constant monitoring, even if there’s a power failure
  • Features an electrochemical carbon monoxide sensing technology as well as an ionization sensor that detects the fine particles of a fast-burning fire
  • Indicator lights on the face of the unit display the presence of smoke or carbon monoxide, while an 85-decibel siren provides a clear, loud warning upon detection
  • Can connect to other compatible BRK or First Alert detectors, to ensure all alarms will sound when a threat is detected
  • Simple to use, with a single test/silence button, and a side-load battery compartment, tamper-resistant locking brackets, and universal mounting brackets make installation easy. Dust cover
  • First Alert has been the most trusted brand in home safety since launching the first residential smoke alarm in 1958 (Based on a First Alert brand trust survey in February 2018)
  • Faster turnarounds on job sites with the easy-to-install, most-trusted alarms in-home safety


  • Brand: First Alert
  • Style: Hardwired Alarm
  • Size: 3 pack
  • Pattern: Detector
  • Power Source: Corded Electric
  • Item Dimensions LxWxH: 5.6 x 5.6 x 2.2 inches
  • Sensor Type: Electrochemical, Ionization
  • Batteries: 2 AA batteries required. (included)