BRK First Alert - SC9120B Smoke & Carbon Monoxide Alarm, Hardwired, 9V Battery




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The First Alert Hardwire Combination Smoke/Carbon Monoxide Alarm wires directly into your home's electrical system. In the event of a power outage, this alarm has been equipped with a 9V battery backup to provide optimal protection. The realization of ionization technology combined with an electrochemical sensor ensure optimal safety. A Mute Button has been included to serve the dual purpose of silencing nuisance alarms brought on by cooking smoke and shower steam. This button also allows you to test the functionality of your alarm. This alarm carries a 10 year limited warranty and complies with new construction requirements.



  • Electrochemical Carbon Monoxide Sensor - the most accurate sensor available as compared to other sensing technologies
  • 9V Alkaline Battery Backup
  • Latching alarm indicator - remembers which unit initiated an alarm
  • Two silence features - can silence the low-battery chirp for up to eight hours or temporarily silence an unwanted nuisance alarm
  • End of Life Signal provides audible notification alarms needs to be replaced
  • Intelligent Sensing TechnologyTM helps reduce the number of nuisance alarms
  • Perfect Mount - allows for easy alignment of alarm
  • Dust Cover
  • 10-Years Limited Warranty

Easy Installation/Maintenance - First Alert SC9120B carbon monoxide alarm & smoke detector Preferred features include a large opening in the mounting bracket for easy access to wiring. Keyhole slots in the mounting bracket eliminate the need to remove the electrical box screws for installation. A battery pull tab keeps the battery fresh until the home is occupied. Battery installation and removal can occur while the unit is mounted to the ceiling or wall via the side load battery compartment. Two locking features are provided to prevent battery theft and/or theft of the unit. Connection to AC power is made with a "Quick-Connect" wiring harness. Installation is quick, easy and cost effective.

All BRK Electronics smoke alarms meet UL 217 standard and are listed with the California State Fire Marshal. They use the new UL mandated repeating 85-decibel alarm horn pattern. 10-year limited warranty. For a full list of states and cities requiring 10 Year alarms click here. 

Customer Reviews

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Ask a Question
  • What determines the "end of life" of the SC 9120B and is it based on date of manufacture or start date of use?

    The end of life for BRK Smoke alarms is 10 years from the manufacturer's date. Nevertheless, alarms may malfunction earlier if the alarm is placed in a humid environment. 

  • Chirping 3 times than stops a little minute or 2than chirps again might stop for a little longer than starts again. We changed the battery at least we put one in the compartment because you can not tell if it is in the slots. We cannot get it to stop chirping.

    The chirp pattern described indicates that the alarm malfunctioned and it needs to be replaced immediately. 

  • where is the mute button ?

    To silence an alarm, you must press the Test/Silence button on the initiating alarm (The unit with the flashing red light; the red light will be off on all other Alarms.). If you press the Test/Silence on any other Alarm, it will only silence that unit, not the whole interconnected series.

  • How do I replace the battery?

    The alarm does not need to be removed to in order to replace the battery. The battery compartment door opens from the side of the unit. 

  • Does this product include adapter plugs?

    Yes. Each unit includes the 6-to-7 inch 3-wire jumper cable (most systems only use two of the wires: the + & -). The rectangular connector plugs into the sensor, and the wires are typically connected to the house wiring via an electrical wire nut (not included, unless you are replacing an existing unit in your house already wired with one - if so then reuse the nut if in good condition). The 9-volt batteries are for backup - Be safe with the electrical wiring and good luck - get professional help if you need it

  • My alarm #9120B is chirping 5 times. I replaced the battery but it is still chirping every few minutes. What is the problem?

    It is likely that the reason your smoke alarm keeps chirping and beeping is that the battery is low and your product has reached the end of its life

  • Can this unit be interconnected?

    Yes the SC9120B is an interconnected alarm

  • what is the manufactured date on these units?

    All of our units in stock were manufactured within the last 2 months

In The Box

  • 1 x Smoke & Carbon Monoxide Alarm
  • 1 x Mounting Bracket
  • 1 x Power Connector
  • 1 x Dust Cover
  • 1 x English/ Spanish Instructions Manual

 Info & Guides

User manual

Spec sheet


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