March 19, 2026

10 Best First Alert Sc9120b of 2026

Last Updated - March 19, 2026

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1

9.9

Outstanding

First Alert SC-9120B Hardwired Smoke and Carbon Monoxide Alarm with Battery Backup 2 Pack

First Alert

Clicked 397 times in the last week

First Alert SC-9120B Hardwired Smoke and Carbon Monoxide Alarm with Battery Backup 2 Pack

Why We Love It

Hardwired CO smoke alarm features battery backup for constant monitoring
Can connect to other compatible BRK or First Alert CO smoke detectors
Lights indicate if the alarm is for smoke or for carbon monoxide
Single test silence button for simple operation
Side-load battery compartment for convenience

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Why We Love It

Hardwired CO smoke alarm features battery backup for constant monitoring
Can connect to other compatible BRK or First Alert CO smoke detectors
Lights indicate if the alarm is for smoke or for carbon monoxide
Single test silence button for simple operation
Side-load battery compartment for convenience

2

9.5

Excellent

First Alert BRK SC-9120B Hardwired Smoke and Carbon Monoxide (CO) Detector with Battery Backup

First Alert

First Alert BRK SC-9120B Hardwired Smoke and Carbon Monoxide (CO) Detector with Battery Backup

Main Highlights

Superior carbon monoxide sensor and dual ionization smoke alarm
Inter-connectable with BRK and First Alert hardwired smoke and carbon monoxide alarms
Easy to install universal mount bracket
Simple to use silence/test button; separate smoke and CO latching alarm indicators
9-volt battery included; 10-year limited warranty
Faster turnarounds on job sites with the easy-to-install, most-trusted alarms in home safety

View Deal on:

Main Highlights

Superior carbon monoxide sensor and dual ionization smoke alarm
Inter-connectable with BRK and First Alert hardwired smoke and carbon monoxide alarms
Easy to install universal mount bracket
Simple to use silence/test button; separate smoke and CO latching alarm indicators
9-volt battery included; 10-year limited warranty
Faster turnarounds on job sites with the easy-to-install, most-trusted alarms in home safety

3

9.5

Excellent

BRK SC9120B Smoke and Carbon Monoxide Alarm

BRK SC9120B Smoke and Carbon Monoxide Alarm

Main Highlights

Superior carbon monoxide sensor and dual ionization smoke alarm
Simple to use silence/test button; separate smoke and CO latching alarm indicators
9-volt battery included; 7-year limited warranty
Inter-connectable with BRK and First Alert hardwired smoke and carbon monoxide alarms
Easy to install universal mount bracket

View Deal on:

Main Highlights

Superior carbon monoxide sensor and dual ionization smoke alarm
Simple to use silence/test button; separate smoke and CO latching alarm indicators
9-volt battery included; 7-year limited warranty
Inter-connectable with BRK and First Alert hardwired smoke and carbon monoxide alarms
Easy to install universal mount bracket

4

9.2

Excellent

First Alert BRK SC9120B-6 Hardwired Smoke and Carbon Monoxide Detector (CO) with Battery Backup. 6-Pack , White

First Alert

First Alert BRK SC9120B-6 Hardwired Smoke and Carbon Monoxide Detector (CO) with Battery Backup. 6-Pack , White

Main Highlights

The First Alert Hardwired Smoke and Carbon Monoxide Alarm with Battery Backup provides 2-in-1 protection from both types of dangers.
Hardwired alarm features battery backup for continued monitoring during power outages.
Includes easy adapter plugs, eliminating the need to rewire.
Light indicates if the alarm is for smoke or for carbon monoxide in the event of an emergency.
A single test button makes alarm easy to test regularly. The alarm is also equipped with a side-load battery compartment and its tamper-resistant locking brackets and universal mounting brackets make installation easy.

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Main Highlights

The First Alert Hardwired Smoke and Carbon Monoxide Alarm with Battery Backup provides 2-in-1 protection from both types of dangers.
Hardwired alarm features battery backup for continued monitoring during power outages.
Includes easy adapter plugs, eliminating the need to rewire.
Light indicates if the alarm is for smoke or for carbon monoxide in the event of an emergency.
A single test button makes alarm easy to test regularly. The alarm is also equipped with a side-load battery compartment and its tamper-resistant locking brackets and universal mounting brackets make installation easy.

5

9.0

Excellent

FIRST ALERT BRK SC9120B-3 Hardwired Smoke and Carbon Monoxide (CO) Detector with Battery Backup, White, Pack of 3

First Alert

FIRST ALERT BRK SC9120B-3 Hardwired Smoke and Carbon Monoxide (CO) Detector with Battery Backup, White, Pack of 3

Main Highlights

Keep your family safe with this 3-pack of hardwired smoke and carbon monoxide alarm; The battery backup means constant monitoring, even if there's a power failure
Features an electrochemical carbon monoxide sensing technology as well as an ionization sensor that detects the fine particles of a fast-burning fire
Indicator lights on the face of the unit display the presence of smoke or carbon monoxide, while an 85-decibel siren provides a clear, loud warning upon detection
Can connect to other compatible BRK or First Alert detectors, to ensure all alarms will sound when threat 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. Dust cover

View Deal on:

Main Highlights

Keep your family safe with this 3-pack of hardwired smoke and carbon monoxide alarm; The battery backup means constant monitoring, even if there's a power failure
Features an electrochemical carbon monoxide sensing technology as well as an ionization sensor that detects the fine particles of a fast-burning fire
Indicator lights on the face of the unit display the presence of smoke or carbon monoxide, while an 85-decibel siren provides a clear, loud warning upon detection
Can connect to other compatible BRK or First Alert detectors, to ensure all alarms will sound when threat 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. Dust cover

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6

8.8

Very Good

First Alert 9120B / SMI100-AC Smoke Detector, Hardwired Alarm with Battery Backup, 3-Pack

First Alert

First Alert 9120B / SMI100-AC Smoke Detector, Hardwired Alarm with Battery Backup, 3-Pack

Main Highlights

Keep your family safe with this 3 pack of hardwired smoke alarms; 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 standards
Faster turnarounds on job sites with the easy to install, most trusted alarms in home safety
First Alert has been the most trusted brand in home safety since launching the first residential smoke alarm in 1958 (Based on a First Alert Brand Trust Survey in February 2018)

View Deal on:

Main Highlights

Keep your family safe with this 3 pack of hardwired smoke alarms; 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 standards
Faster turnarounds on job sites with the easy to install, most trusted alarms in home safety
First Alert has been the most trusted brand in home safety since launching the first residential smoke alarm in 1958 (Based on a First Alert Brand Trust Survey in February 2018)

7

8.6

Very Good

BRK First Alert 9120BFF/ SMI100-AC Smoke Detector, Hardwired Alarm with Battery Backup, White, 1-Pack

BRK

BRK First Alert 9120BFF/ SMI100-AC Smoke Detector, Hardwired Alarm with Battery Backup, White, 1-Pack

Main Highlights

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
First Alert has been the most trusted brand in home safety since launching the first residential smoke alarm in 1958 (Based on a First Alert Brand Trust Survey in February 2018)
Faster turnarounds on job sites with the easy-to-install, most-trusted alarms in home safety

View Deal on:

Main Highlights

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
First Alert has been the most trusted brand in home safety since launching the first residential smoke alarm in 1958 (Based on a First Alert Brand Trust Survey in February 2018)
Faster turnarounds on job sites with the easy-to-install, most-trusted alarms in home safety

8

8.3

Very Good

FIRST ALERT BRK SC9120FF Hardwired Smoke and Carbon Monoxide (CO) Detector with Battery Backup, 1 pack , White

First Alert

FIRST ALERT BRK SC9120FF Hardwired Smoke and Carbon Monoxide (CO) Detector with Battery Backup, 1 pack , White

Main Highlights

Keep your family safe with this hardwired smoke and carbon monoxide alarm; The battery backup means constant monitoring, even if there's a power failure
Features an electrochemical carbon monoxide sensing technology as well as an ionization sensor for smoke detection.
Indicator lights on the face of the unit display the presence of smoke or carbon monoxide, while an 85 decibel siren provides a clear, loud warning upon detection
Can connect to other compatible BRK or First Alert detectors, to ensure all alarms will sound when threat 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 standards
Faster turnarounds on job sites with the easy-to-install, most-trusted alarms in home safety
First Alert has been the most trusted brand in home safety since launching the first residential smoke alarm in 1958 (Based on a First Alert Brand Trust Survey in February 2018)

View Deal on:

Main Highlights

Keep your family safe with this hardwired smoke and carbon monoxide alarm; The battery backup means constant monitoring, even if there's a power failure
Features an electrochemical carbon monoxide sensing technology as well as an ionization sensor for smoke detection.
Indicator lights on the face of the unit display the presence of smoke or carbon monoxide, while an 85 decibel siren provides a clear, loud warning upon detection
Can connect to other compatible BRK or First Alert detectors, to ensure all alarms will sound when threat 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 standards
Faster turnarounds on job sites with the easy-to-install, most-trusted alarms in home safety
First Alert has been the most trusted brand in home safety since launching the first residential smoke alarm in 1958 (Based on a First Alert Brand Trust Survey in February 2018)

9

8.1

Very Good

First Alert BRK 9120B/ SMI100-AC Smoke Detector, Hardwired Alarm with Battery Backup, 3-Pack

First Alert

First Alert BRK 9120B/ SMI100-AC Smoke Detector, Hardwired Alarm with Battery Backup, 3-Pack

Main Highlights

Imported
Tamper resistant locking pins, single button silence test and loud 85dB alarm
120-Volt AC power with 9-Volt battery backup (included) to keep alarm functioning during power outage

View Deal on:

Main Highlights

Imported
Tamper resistant locking pins, single button silence test and loud 85dB alarm
120-Volt AC power with 9-Volt battery backup (included) to keep alarm functioning during power outage

10

8.1

Very Good

First Alert 9120B 120 Volt Hardwired Smoke Alarm With Battery Back Up 5 Pack

First Alert

First Alert 9120B 120 Volt Hardwired Smoke Alarm With Battery Back Up 5 Pack

Main Highlights

Imported
Tamper resistant locking pins, single button silence test and loud 85dB alarm
120-Volt AC power with 9-Volt battery backup (included) to keep alarm functioning during power outage

View Deal on:

Main Highlights

Imported
Tamper resistant locking pins, single button silence test and loud 85dB alarm
120-Volt AC power with 9-Volt battery backup (included) to keep alarm functioning during power outage