Customer Reviews For The First Alert Hardwired Inter-connected Smoke Alarm, 9120

Overall Rating

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8 Reviews
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8 customers recommend this product
Joe Dure
May 7, 2026
Perfect

The First Alert 9120 is the gold standard for reliable, hardwired smoke detection. I recently replaced several units in my home that were nearly 20 years old, and the process couldn't have been easier. Because First Alert has maintained consistent design standards, the new 9120 units snapped right into my existing mounting brackets and used the same wiring harness. What I expected to be an afternoon-long project was finished in under twenty minutes.

Willy Sorenson
November 29, 2015
Verified Purchase
All installed

I purchased 8 of these to swap out the existing First Alert smoke detectors we got with the house 15+ years ago. The connections were the same so the install was less than 2 minutes each. Same size also.

Katherine Hodson
November 10, 2015
Verified Purchase

I was able to replace the discontinued item with this one. For someone who is not familiar with doing this type of stuff I was happy I was able to do it without asking for help.

Patricia Copeland
November 6, 2015
Verified Purchase
First Alert 9120

Simple to install. Bought to replace SA86??, it was probably 20 years old.

Dianne  Watts
September 7, 2015
Verified Purchase
thank you

very quick service, thought I was ordering a battery backup one, but they are working. thanks

Terry Friend
July 6, 2015
Verified Purchase
hardwired smoke alarm

it showed up on time, so far, so good. We will always use First Alert.

Joe Jozefczyk
January 27, 2015
Verified Purchase
Excellent customer service

Our smoke alarm had lived a long and useful life but when it came time to replace it, I couldn't find the most recent/comparable model. I called First Alert and the rep was very helpful and professional. Based on his recommendation, I purchased a new smoke alarm which is working perfectly!!!

James Boggess
December 4, 2014
Verified Purchase
no problems

the smoke alarms came promptly and were the ones I ordered. Thank you for prompt service.

First Alert 9120 Hardwired Interconnected Smoke Alarm with Battery Backup

The First Alert 9120 is a professional-grade, hardwired smoke alarm designed to provide a high level of fire safety for residential homes and commercial properties. As a 120V AC direct-wire unit, it integrates seamlessly into your building's electrical system to ensure constant, reliable protection. One of the most critical features of the 9120 is its interconnectivity capability. When properly installed, this alarm can be linked with up to eighteen other First Alert or BRK compatible devices, including twelve smoke alarms and six carbon monoxide or heat alarms. This "one-act-all-act" system ensures that if smoke is detected in a distant basement or garage, every interconnected alarm throughout the entire house will sound simultaneously, providing precious extra seconds for evacuation during a fire emergency.

  • Interconnected System: Connects with up to 18 devices so all alarms sound when one is triggered.
  • Dual Power Reliability: 120V AC hardwired connection with 9V battery backup for power outages.
  • Advanced Ionization Sensor: Specifically designed to detect fast-flaming fires quickly.
  • Easy Battery Access: Features a side-loading drawer for quick battery changes without dismounting.
  • Single-Button Function: Centralized button for functional testing and silencing of nuisance alarms.
  • Loud 85dB Siren: Penetrating alarm ensures notification is heard throughout the residence.
  • Quick-Connect Harness: Simplified wiring system for faster and safer installation.
  • UL Standards Certified: Fully compliant with UL217 benchmarks for residential fire safety.
  • Ten-Year Warranty: Includes a limited manufacturer warranty for a full decade of protection.

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