BRK Hardwired Interconnected Smoke Alarm with Battery Backup-9120B - The Home Depot
Message to Our Customers


Model # 9120B

Internet # 100065881

Hardwired Interconnected Smoke Alarm with Battery Backup

BRK Hardwired Interconnected Smoke Alarm with Battery Backup

This item has been discontinued.
The Home Depot no longer carries this specific product.

$14.97 / each


Model # 9120B

Internet # 100065881

The BRK 9120B 120-Volt AC Smoke Alarm with Battery Backup is designed to install faster, perform better, and be even smarter than before. This alarm is 120-volt AC inter-connectable (with maximum 18 compatible devices), which lets the alarm be interconnected with up to 12 other compatible smoke alarms and six compatible devices like bells, horns, repeaters, and door closers to network a comprehensive system for your home. If one unit triggers an alarm, all smoke alarms in the series will sound. The 9120B includes an ionization sensor which helps detect fast flaming fires that consume combustible materials rapidly. The dust-reducing packaging helps avoid accidental alarms due to contaminants and the 85 dB horn can be inspected with a test button. This unit includes a quick-connect wiring harness for easier installation to your household current and 9-volt battery backup ensures protection even during power outages or service interruptions. 10-year limited warranty.

  • 120V AC Smoke Alarm with Battery Backup
  • 85 dB horn sounds as smoke reaches dangerous levels
  • Can be interconnected with 12 additional BRK and First Alert Smoke Alarms and 6 compatible devices such as heat alarms for a complete safety system
  • Dust-blocking covers to reduce nuisance alarms associated with particulate contamination
  • Locking pins deter removal
  • A single button tests units functionality and silences nuisance alarms
  • 9-volt battery backup ensures operation during household current interruption
  • Power indicator lets you see at a glance that the alarm is powered
  • Universal mounting bracket with wide opening for easy wire access
  • Meets UL standards

Info & Guides

You will need Adobe® Acrobat® Reader to view PDF documents. Download a free copy from the Adobe Web site.


Product Depth (in.) 
Product Height (in.) 
Product Width (in.) 
Alarm Sensor Type 
Alarm Type 
Alarm/Detector Features 
No Additional Features 
Battery Back-Up 
Battery Power Type 
Battery Size 
Commercial / Residential 
Commercial / Residential 
Connector/Contact Type 
Electrical Product Type 
Smoke Detector 
Power Source 
Voltage (volts) 
Warranty / Certifications
Certifications and Listings 
1-UL Listed 


Rated 4.1 out of 5 by 62 reviewers.
Rated 5.0 out of 5.0 by Easy to install We bought two to replace older hard wired smoke alarms. Clear instructions and a very easy installation. They're new so we can't comment yet on their longevity nor performance. December 31, 2013
Rated 5.0 out of 5.0 by Performs as advertised We installed a combination of fifteen interconnected hard-wire and wireless smokes along with three interconnected wireless CO detectors. All eighteen linked together just as advertised and worked flawlessly. Here's to hoping we never need them but if we do, then we can sleep comfortably knowing we're well protected. October 15, 2013
Rated 5.0 out of 5.0 by BRK 9120B Bought our home new in 1999. The smoke alarms installed at that time were BRK 4150B. After 12 years they started to chirp even when new batteries were installed. I have read where dust will make any smoke alarm defective over time. So I replaced all 8 of them with the new BRK 9120B which has the battery backup and which used the same plug, but different base plate. It took me only 30 min to install all 8 of these smoke alarms. I tested them all and they all work perfectly. I then tested with a napkin on fire to see if all 8 of would go off at the same time and they did. I am a happy camper and easy install. February 6, 2014
Rated 5.0 out of 5.0 by good smoke With a 10 yr battery how can u go wrong. easy install April 14, 2015
Rated 4.0 out of 5.0 by Good replacement for earlier smoke detectors I had to replace four 15 year old First Alert smoke detectors. The 9120 had the same footprint, the same wire connection and the instillation was a snap. It took about a half an hour. The 9120 has upgraded features and design improvements that are well worthwhile. February 12, 2013
Rated 4.0 out of 5.0 by Safety The smoke detectors were easy to install, the only problem I had was getting one of them apart to install. I left one of the old ones installed. Other than that , I received the package quicker than expected, and in oood condition. This was important to me as I had been without working detectors for 3 months until I could afford to buy them. March 25, 2015
Rated 5.0 out of 5.0 by Replacing fire alarms I originally bought these as a six pack at Lowes but after only 5 years of service they needed replaced. You had the replacement cheaper so I bought them at Home Depot thanks for the fast delivery. March 24, 2015
Rated 5.0 out of 5.0 by Definitely recommend! Happy with my purchase. Bought two of these alarms. Easy to install. Very easy to change back-up battery. No false alarms. January 10, 2014
  • 2015-05-04T11:05:00.618-05:00
  • bvseo_lps, prod_bvrr, vn_prr_5.6
  • cp-1, bvpage1
  • co_hasreviews, tv_62, tr_62
  • loc_en_US, sid_100065881, prod, sort_default
2 3 >>


Standard Shipping includes delivery by small parcel service. Processing time varies by product.

If product is eligible for shipping to AK, HI and US Territories additional transit time and remote surcharges may apply.