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First Alert AC Smoke Alarm with Battery Backup

SKU: BR9120B

Usually ships in 3-5 days.


WARNING: Cancer and Reproductive Harm –


Reduce Nuisance Alarms & Stay Protected

Smarten up your home's smoke detection with the First Alert Smoke Detector, AC Power with Battery Backup. This full-featured First Alert smoke detector incorporates smart technology to reduce "nuisance alarms" and increase true alarm performance. This First Alert smoke alarm is cost-effective and reliable, keeping you safe around the clock.

  • Single button test/silence
  • Latching alarm indicator
  • Smart Technology reduces nuisance alarms
  • Perfect Mount allows for easy alignment during installation
  • Dust cover protects unit during construction
  • Improved UV Resistance keeps the alarm from discoloring over time
  • Battery backup ensures operation during power outages

Smart Technology

The First Alert Smoke Detector includes multiple features that increase reliability and decrease the hassle that typical smoke detectors comprise. The First Alert smoke alarm's dual ionization sensing chamber is more effective at detecting small particles produced by flaming fires. Sources may include paper or kitchen grease. The First Alert Smoke Detector is also interconnectable with up to 18 devices (12 can be smoke alarms), allowing you to protect your home with a detection system rather than individually operating units.

Latching Alarm Indicator

As part of the Smart Technology system, the Latching Alarm feature remembers which detector in your home initiated an alarm. When interconnected in a series of detectors, the unit that triggered the alarm rapidly flashes its red LED indicator. After the alarm condition subsides, the initiating unit will store in memory or "latch" the information and begin to flash the green LED indicator two seconds on, two seconds off, signaling the source of smoke.

First Alert Interconnect Alarms

This First Alert Alarm can be integrated into a mesh network with other First Alert Alarms using “Interconnect Technology”. First Alert Interconnect Alarms operate on a mesh network that integrates multiple wireless or wired alarms for better safety and response in an emergency. The mesh network of alarms re-routes and resends the signal via other First Alert alarms, providing a greater chance all alarms will receive the signal. Up to 18 total units can be interconnected, wireless or hardwired: with a maximum of 12 smoke alarms and 6 carbon monoxide alarms. Ordinarily, wireless and hardwired alarms cannot work together on the same interconnected network. However, with the hardwired bridge unit (model SA520B), hardwired and wireless models can be interconnected together on the same mesh network.


  • Smoke detector
  • Dust cover
  • Mounting bracket
  • Installation components

Requires the 120VAC Smart Relay (sold separately) to activate an alert device.

FirstAlert: A Leader In Saving Lives

You can install FirstAlert products with confidence! Our products are designed to save lives. It's a responsibility we don't take lightly. We build each smoke alarm, carbon monoxide alarm, heat alarm, and fire extinguisher to the highest standards. Over the years, we've seen competitors come and go. We're still here, still making the most recognized consumer brands of smoke and CO alarms on the market.



  • Alarm Sounds
  • Power Up Indication
  • Supervisory Chirp

Technical Details

  • Alarm Dimensions: 5.6(Dia.) x 2(H) inches
  • Weight: 7.8 ounces
  • Operating Voltage: 120V AC 60Hz
  • Operating Current: 0.04 Amps (standby/alarm)
  • Temperature Range: 40 to 100° F (4 to 38° C)
  • Humidity Range: 10 to 90 percent relative humidity (RH)
  • Audio Alarm: 85dB at 10 feet
  • Test/Silence: Electronically simulates smoke condition, causing the unit to alarm. Press and hold test/silence button.
  • Alarm Reset: Automatic when smoke clears
  • Interconnections: Up to 18 units of First Alert or BRK Smoke, CO and Heat Alarms. Maximum of 12 smoke alarms. See user's manual for details.
  • Smoke Sensor: Dual chamber ionization
  • Indicator Lights/Sounds:
    • AC Power: Constant Green LED
    • DC Power: Intermittent Red LED
    • Local Alarm: Red LED flashes rapidly
    • Remote Alarm: Red LED out
    • Latching Alarm: Green LED flashes 2 seconds on/2 seconds off after local alarm
  • Listing: Listed to UL217 Standard
  • Warranty: 10 Years Limited