BRK 9120B Hardwired Ionization Smoke Alarm, Interconnectable with Battery Backup

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BRK 9120B Hardwired Ionization Smoke Alarm, Interconnectable with Battery Backup

Name: BRK 9120B Hardwired Ionization Smoke Alarm, Interconnectable with Battery Backup
Brand: BRK
SKU: 9120B
Price: 19.91 USD
Availability: InStock
Rating: 4.85 (13 reviews)

BRK SKU: 9120B Smoke Detector GTIN: 029054015327

★ ★ ★ ★ ★ 4.85 (13 verified reviews)

$19.91 $30.99

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EDITORIAL REVIEW: 4.5/5 WC Safety Review — BRK 9120B Hardwired Ionization Smoke Alarm — Interconnectable Editorial assessment by the WC Safety Editorial Team, based on published BRK specifications and category fit...

Key Features

Keep your family safe with this hardwired smoke alarm the battery backup means constant monitoring, even if there's a power failure
Equipped with an ionization sensor, this smoke alarm reliably detects smoke from fast flaming fires and alerts you with an 85 decibel alarm
To ensure complete protection make sure to place one on each level of your home and in each bedroom
Can connect to other compatible BRK or first alert smoke detectors, to ensure all alarms will sound when smoke is detected
Simple to use, with a single test/silence button, and side load battery compartment tamper resistant locking brackets and universal mounting brackets make installation easy
Rigorously tested to meet UL standards120 volt AC power with 9V battery backup to keep alarm functioning during power outage

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9120B 9120BFF BRK restructured Smoke Detectors & Fire Alarms White

EDITORIAL REVIEW: 4.5/5 WC Safety Review — BRK 9120B Hardwired Ionization Smoke Alarm — Interconnectable

Editorial assessment by the WC Safety Editorial Team, based on published BRK specifications and category fit. We did not laboratory-test this product.

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BRK 9120B Hardwired Ionization Smoke Alarm, Interconnectable with Battery Backup Overview

The BRK 9120B is a 120V AC hardwired ionization smoke alarm with 9V battery backup, designed to be interconnected so that when one unit detects smoke, every linked alarm in the home sounds. It is a smoke-only alarm tested to the UL 217 smoke-alarm standard; it does not detect carbon monoxide. If your goal is CO coverage as well, pair it with a dedicated carbon monoxide alarm or choose a combination smoke/CO alarm.

Ionization sensing reacts fast to flaming, fast-moving fires. The hardwired connection keeps the unit powered from house wiring, while the replaceable battery maintains protection during a power outage. Because alarms are interconnected, a fire starting in a basement or garage triggers the bedroom units too, buying critical escape time. Browse more options in smoke detectors, or compare top picks in our best smoke detectors guide.

Mount one on every level of the home, inside each bedroom, and outside each sleeping area, following the spacing in the BRK installation instructions. Smoke alarms should be replaced about every 10 years from the date of manufacture printed on the back of the unit. For setup and monthly testing, see how to test a smoke & CO alarm.

What It Is Built For

Use case	Fit	Buyer guidance
Whole-home hardwired smoke protection	Excellent	Wire one on every level and near each sleeping area; interconnect so all alarms sound together when one detects fire.
Fast-flaming fire detection (kitchens, garages, living areas)	Excellent	Ionization sensing responds quickly to flaming fires; mount per spacing instructions, away from cooking steam to limit nuisance trips.
Replacing a failed interconnected BRK/First Alert smoke alarm	Excellent	Compatible with standard 3-wire interconnect harnesses; confirm your existing connector and AC voltage before swapping.
Carbon monoxide protection	Not suitable	This unit detects smoke only. Add a separate CO alarm or a combination smoke/CO unit for colorless, odorless CO.
Smoldering-fire-prone areas (bedrooms with upholstery)	Limited	Ionization excels at flaming fires; consider adding a photoelectric or dual-sensor alarm where slow, smoldering fires are a concern.
Homes without existing AC wiring at the alarm location	Not suitable	This is a 120V hardwired unit; choose a battery-only smoke alarm where no AC wiring is present.

A smoke alarm and a carbon-monoxide alarm detect different hazards — install both (or a combination unit) on every level and near each sleeping area, and interconnect them where possible. Test monthly and replace at the unit's end-of-life date (CO sensors typically last 5–10 years; smoke alarms about 10). Carbon monoxide is colorless and odorless, so a working alarm is your only warning — look for UL 2034 (CO) / UL 217 (smoke) listing. See how to test a smoke & CO alarm and the CO detector placement guide.

Pros & Cons

Pros

Hardwired 120V power with 9V battery backup keeps it active during outages
Interconnects so one detected fire sounds every linked alarm in the home
Ionization sensor reacts quickly to fast-flaming fires
Continuous house-current power means no reliance on battery alone
Compatible with standard BRK/First Alert interconnect wiring for easy upgrades

Cons

Smoke only, it does not detect carbon monoxide
Ionization sensing is less responsive to slow smoldering fires than photoelectric
Requires existing 120V AC wiring, not a plug-in or standalone battery unit
Battery backup must be replaced periodically, not a sealed 10-year cell
Like all smoke alarms, must be replaced about every 10 years

How It Compares

The BRK 9120B is the workhorse hardwired, interconnectable ionization smoke-only alarm: it links across the home and runs on house current with battery backup. If you want a sealed unit with no annual battery swaps, look to a 10-year sealed-battery smoke alarm instead; if a location lacks AC wiring, a battery-only model like the kidde i9010 ionization smoke alarm or the kidde 10sdr battery operated smoke alarm fits better.

Remember the 9120B covers fire only. For colorless, odorless carbon monoxide you need a separate device such as the first alert co250 carbon monoxide alarm, or browse all CO detectors. A complete home setup pairs interconnected smoke alarms with CO coverage on every sleeping level.

Specifications

Detects	Smoke only (not carbon monoxide)
Sensing type	Ionization (fast-flaming fire response)
Power	120V AC hardwired with 9V battery backup
Interconnect	Yes, links with compatible BRK/First Alert devices so all sound together
Standard	Tested to UL 217 smoke-alarm requirements
Display	None (audible alarm with status indicator)
Recommended replacement	About every 10 years from manufacture date
Brand / Model	BRK 9120B

Related Resources

CO detectors smoke detectors carbon monoxide alarms combination smoke/CO alarms gas detectors best CO detectors best smoke detectors CO detector placement guide how to test a smoke & CO alarm kidde kn copp b lpm battery carbon monox

Frequently Asked Questions

Does the BRK 9120B detect carbon monoxide?

No. The 9120B is a smoke-only alarm. It detects smoke from fire and does not sense carbon monoxide, which is colorless and odorless. For CO protection, add a separate carbon monoxide alarm or a combination smoke/CO unit.

Is the BRK 9120B hardwired or battery-powered?

It is a 120V AC hardwired alarm with a 9V battery backup. It draws power from your home's wiring and the battery keeps it working during a power outage. It is not a plug-in or battery-only unit.

What type of sensor does the 9120B use?

It uses ionization sensing, which responds quickly to fast-flaming fires. Ionization is generally less responsive to slow, smoldering fires, so some homes add a photoelectric or dual-sensor alarm in bedrooms for broader coverage.

Can I interconnect the 9120B with my existing smoke alarms?

Yes. The 9120B is interconnectable and links with compatible BRK and First Alert devices using standard 3-wire interconnect. When one alarm detects smoke, all connected alarms sound. Confirm your existing connector and voltage before installing.

How many alarms can be interconnected together?

BRK hardwired alarms in this family typically support interconnecting multiple compatible smoke and CO devices on one circuit, up to the limit listed in the BRK installation manual. Always follow the wiring count and device-compatibility limits printed in the included instructions.

Is the BRK 9120B UL listed?

It is built to the UL 217 standard that applies to residential smoke alarms. UL 217 covers smoke detection performance; carbon monoxide alarms fall under a different standard (UL 2034), which does not apply here since this is a smoke-only device.

Where should I install the 9120B?

Install a smoke alarm on every level of the home, inside each bedroom, and outside each sleeping area, following the spacing in the instructions. Keep it away from kitchens and bathrooms where steam can cause nuisance alarms. See our smoke and CO testing guide for setup help.

Does the battery backup need replacing?

Yes. The 9120B uses a replaceable 9V backup battery rather than a sealed 10-year cell. Replace the battery on the schedule in the manual (commonly once a year) and whenever the low-battery chirp sounds, so backup power is always ready.

How often should I replace the alarm itself?

Smoke alarms should be replaced about every 10 years from the date of manufacture printed on the back of the unit. After that, sensor reliability declines and the whole alarm should be swapped, not just the battery.

Will the 9120B work without AC wiring?

No. It is designed for 120V hardwired installation. If a location has no AC wiring, choose a battery-only smoke alarm such as a 9V or sealed-battery model instead of this hardwired unit.

Do I need a CO alarm too?

Yes, for complete home safety. The 9120B covers fire only. Carbon monoxide is colorless and odorless, so you need a dedicated CO alarm or a combination smoke/CO alarm on every sleeping level in addition to your interconnected smoke alarms.

How do I test the BRK 9120B after installation?

Press and hold the test button until the alarm sounds, and test every interconnected unit monthly to confirm the whole system sounds together. Our step-by-step guide on how to test a smoke and CO alarm walks through testing interconnected and standalone units.

Written by Steven Eaton, WC Safety Editorial. Specifications sourced from BRK published data. Compare the range in carbon monoxide & smoke alarms.

WC Safety is an independent PPE retailer and Amazon Associate; no paid placement. Match the product to your specific hazard and follow your site PPE program.

Brand / Vendor

BRK

Model / SKU

9120B

Product Type

Smoke Detector

Condition

New

MPN

9120B

Price

$19.91 (Amazon)

Rating

4.85 / 5 — 13 reviews

Availability

✓ In Stock on Amazon

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Customer Reviews

★★★★★4.8 / 5· 13 verified reviews

★★★★★

Great alarm at a generic price!

It took me a long time to decide which smoke detectors to buy for my house, this model or the brand made by Kiddie. My house already had the Kiddie brand and this would mean a much faster replacement for all the smoke detectors in my house. Over time the Kiddie brand tended to chirp a lot and that drove everyone in the house crazy, especially my older and wonderful dog. My daughter said a candle lit in her room also set off all the smoke detectors in our house.