Pros / It includes dual-sensor functionality that can detect smoldering fires and flaming fires.

Cons / It lacks an automatically illuminating safety light.

 Verdict / One of the best smoke detectors available, the First Alert BRK 3120B can interconnect with as many as 18 other devices and comes equipped with dual-sensor technology that provides maximum protection against different types of fires.

Editor's Note: This review has been removed from our side-by-side comparison because it no longer ranks as a top 10 product. The original review is below, but check out our current top 10 about Smoke Detectors here.

The First Alert BRK 3120B distinguishes itself as one of the best hardwired smoke detectors on the market today. Equipped with dual-sensor technology, this smoke alarm can alert you to the presence of smoke in your home emanating from smoldering fires or fast-burning, raging fires. It can interconnect with as many as 18 First Alert devices and comes with a 10-year manufacturer warranty.

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Detection & Alerts

The First Alert BRK 3120B smoke alarm is manufactured with dual-sensor capabilities, including a photoelectric sensor and an ionization sensor. Photoelectric sensors are better at detecting the presence of smoke coming from slow-burning, smoldering fires. Ionization sensors are better for detecting flaming fires. When combined into a single unit, these two technologies can keep you protected from different types of fires that may break out from a variety of sources.

This unit does not include a carbon monoxide (CO) detector; however, it should be noted that depending on the types of appliances you have in your home, you may not need one at all. CO detectors should be installed in homes with fuel-burning appliances, fireplaces or attached garages but may not be necessary in every room of your home. For optimal coverage against carbon monoxide, fast-burning fires and smoldering fires, we recommend installing a CO detector on every level of your home in addition to First Alert BRK 3120B units in every room. 


A key benefit of this hardwired smoke alarm is that it connects to your home’s electrical system and only requires battery power in the event of a power outage. Battery backup is provided by two AA batteries. Since battery power is only used during power outages, this means you may achieve greater longevity from your batteries – although it is strongly recommended that you replace your batteries at least once every 12 months.

Unlike the vast majority of wireless smoke alarms, which operate independently of one another, the BRK 3120B can interconnect with as many as 18 other First Alert units, including smoke, CO and heat alarms. The maximum limit of First Alert smoke alarms it can interconnect with is 12. Interconnected smoke detectors cause all alarms to go off if only one of them is activated, which can better notify you to the presence of a hazard in your home. Interconnectivity is highly beneficial if you have smoke detectors installed in your basement, garage or closed-off back rooms that might make it difficult to hear if a single alarm were to sound off.

Because this smoke alarm is powered by your home’s electrical system, it may not work in older homes that have not been retrofitted for smoke detector connectivity. Before you purchase a smoke alarm, contact an electrician to explore your options and to see if you would be better off opting for battery-operated smoke alarms.


The First Alert BRK 3120B includes standard features, including an alarm hush button that can be used to silence an alarm that’s been tripped. The same button can be used to test the alarm function, and it’s recommended that you do this once per week to ensure the unit is free of defects and operating properly. The front face of the unit also includes an LED indicator light that flashes when the backup batteries need to be replaced. This flashing light is accompanied by an audible chirp that goes off approximately once per minute when battery power is low. An additional feature of the First Alert BRK 3120B is a low-battery silencer feature that can mute the repetitive chirp for up to eight hours. The smoke detector’s alarm sounds off at 85 decibels, which is standard for all smoke alarms manufactured and sold in the U.S.


The First Alert BRK 3120B is one of the best-rated hardwired smoke detectors we evaluated. Due to the fact it is manufactured with both a photoelectric sensor and an ionization detector, it is better equipped to detect different kinds of fires. Interconnectivity with up to 18 First Alert devices and 12 First Alert smoke alarms ensures you are alerted immediately if a fire breaks out in your home. Its 10-year warranty protects you against defects and numerous avenues for getting help and support can deliver maximum peace of mind.

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