5 Best First Alert and BRK Hardwired Smoke Detectors (November 2026)

The best First Alert and BRK hardwired smoke detectors include the BRK First Alert 9120BFF/ SMI100-AC Smoke Detector for standard smoke protection, the First Alert BRK SC9120B-6 Hardwired Smoke for whole-home smoke and CO coverage, and the First Alert 9120B / SMI100-AC Smoke Detector for multi-room smoke upgrades.

On this page (5 sections)

1. Which First Alert and BRK hardwired smoke detector is best?
2. How do First Alert hardwired smoke alarms compare with other options?
3. How many hardwired smoke alarms should you install?
4. What should you check before installing a hardwired smoke alarm?
5. What is the best First Alert smoke detector hardwired choice?

The best First Alert smoke detector hardwired option for most homes is the BRK First Alert 9120BFF/SMI100-AC, with ionization smoke detection, 120V AC power, a 9V battery backup, and an 85 decibel alarm.

Choose the First Alert SC9120B-6 if you want smoke and carbon monoxide coverage across several rooms.

Hardwired alarms suit homes with existing alarm wiring and can keep working from a battery during a power outage.

That backup matters in daily use because a fire risk does not pause when the power goes out.

Interconnection also means one alarm can trigger other compatible alarms, which can make an alarm easier to hear in another room.

This is especially useful in larger or multi level homes where a single alarm may be hard to hear from a bedroom or kitchen.

If you need a basic explanation before comparing models, start with this guide to what is a smoke alarm.

For a wider look at wired options, see our picks for the best hardwired smoke detectors.

Our score weighs specs, features, and buyer feedback against the needs of someone shopping for the best First Alert smoke detector hardwired setup.

We checked the stated sensor type, backup power, alarm type, pack size, and interconnection details.

We also looked at how each model fits a real replacement job, including mounting, battery access, and test controls.

No single alarm suits every room, so the best choice depends on whether you need smoke only coverage or smoke and CO coverage.

The models here give you clear options for a single replacement, a small multi room upgrade, or a broader whole home update.

Our picks at a glance

1. 1
   Best for standard smoke protection

   BRK First Alert 9120BFF/ SMI100-AC Smoke Detector

   9.7/10 our score

   See it on Amazon
2. 2
   Best for whole-home smoke and CO coverage

   First Alert BRK SC9120B-6 Hardwired Smoke

   9.7/10 our score

   See it on Amazon
3. 3
   Best for multi-room smoke upgrades

   First Alert 9120B / SMI100-AC Smoke Detector

   9.7/10 our score

   See it on Amazon

4. 4

   Siterlink Hardwired Interconnected Smoke Detectors

   Best for photoelectric detection
   Check it
5. 5

   FIRST ALERT BRK SC9120FF Hardwired Smoke

   Best for one-room smoke and CO replacement
   Check it

Which First Alert and BRK hardwired smoke detector is best?

The BRK First Alert 9120BFF/SMI100-AC is the best standard smoke alarm here, while the SC9120B-6 is the strongest choice for broad smoke and CO coverage. The other models fit buyers who need a 3-pack, photoelectric sensing, or a single combination alarm.

1

BRK First Alert 9120BFF/ SMI100-AC Smoke Detector: Best for standard smoke protection

9.7/10Our score

• Hardwired alarm with battery backup
• Ionization sensor
• 85 decibel alarm
• Compatible BRK and First Alert interconnection

This 1-pack is a strong fit for replacing a standard hardwired smoke alarm. It combines ionization detection, a battery backup, and a single test or silence button.

See it on Amazon

Pros

• Battery backup
• 85 decibel alarm
• Tamper-resistant locking brackets

Cons

• Smoke-only alarm
• Ionization sensor is aimed at fast flaming fires

The BRK First Alert 9120BFF/SMI100-AC is the best fit for a home replacing a standard hardwired smoke alarm. Its ionization sensor is designed for smoke from fast flaming fires, and its 85 decibel alarm gives a clear audible warning.

The alarm connects to 120V AC power and includes a 9V battery backup for continued operation during a power failure. A single test and silence button makes routine checks simple, while the side-load battery compartment avoids removing the alarm from its mounting position just to reach the battery.

This 1-pack includes the smoke detector, batteries, and mount. Its universal mounting bracket and tamper-resistant locking brackets help with a replacement project, but you should still match the existing wiring and compatible alarm family before installation.

The model can connect to compatible BRK or First Alert smoke detectors. That makes it a sensible choice when your home already uses compatible hardwired alarms and you want the alarms to sound together.

2

First Alert BRK SC9120B-6 Hardwired Smoke: Best for whole-home smoke and CO coverage

9.7/10Our score

• Smoke and carbon monoxide detection
• 6-pack
• 9V battery backup
• Indicator distinguishes smoke from CO

Six combination alarms cover several rooms at once, with smoke and carbon monoxide detection in each unit. Adapter plugs can help with installation without rewiring.

See it on Amazon

Pros

• Smoke and CO protection
• 6-pack
• Adapter plugs included

Cons

• More coverage than a small home may need
• Hardwired installation still needs planning

The First Alert BRK SC9120B-6 is the best choice when you need smoke and carbon monoxide protection in several rooms. Each alarm combines an ionization smoke sensor with electrochemical CO sensing and has a 9V battery backup.

The 6-pack includes six alarms, six 9-volt batteries, and six mounting brackets. Adapter plugs can help with installation by reducing the need to rewire an existing setup, though you should confirm the connection and model compatibility before starting.

Indicator lights distinguish whether an alarm is responding to smoke or carbon monoxide. A single test button supports regular checks, and the side-load battery compartment keeps battery access straightforward.

This pack makes sense for a larger home, a multi-level layout, or a planned replacement of several combination alarms. If you only need smoke detection, the 9120B 3-pack avoids paying for CO sensing in each unit.

For more detail on voice features, compare it with the best hardwired smoke detectors with voice alerts.

3

First Alert 9120B / SMI100-AC Smoke Detector: Best for multi-room smoke upgrades

9.7/10Our score

• 3-pack
• Ionization sensor
• 85 decibel alarm
• Hardwired interconnection with battery backup

The 3-pack suits a smaller home or a partial replacement where several hardwired smoke alarms need the same style of coverage. Each alarm includes a mounting bracket with hardware.

See it on Amazon

Pros

• Useful 3-pack size
• Battery backup
• Single test and silence button

Cons

• Smoke-only detection
• Ionization sensor does not add CO detection

The First Alert 9120B / SMI100-AC 3-pack is the best match for replacing several smoke-only alarms at once.

Each unit uses an ionization sensor, an 85 decibel alarm, hardwired power, and a 9V battery backup.

That combination is aimed at fast flaming fires, where smoke builds quickly and a loud audible warning matters.

The pack includes three alarms, three batteries, and three mounting brackets with hardware.

That makes it useful when alarms on several levels or in several bedrooms need the same replacement model.

Having matching units can also make setup simpler, because you follow the same mounting and testing steps in each location.

A single test and silence button handles routine checks and temporary silencing.

That plain control suits homes where different family members may need to test the alarm without learning a more complex interface.

The alarms can connect to compatible BRK or First Alert detectors, allowing connected units to sound when one alarm detects smoke.

For daily care, keep the alarm face clear, test it as directed, and replace the backup battery when the low battery warning sounds.

This is a better fit than the 6-pack when you need three units and do not need carbon monoxide detection in each room.

It is also a more focused option than the combination models if your existing safety plan already uses separate CO alarms.

4

Siterlink Hardwired Interconnected Smoke Detectors: Best for photoelectric detection

9.7/10Our score

• 6-pack
• Photoelectric sensor
• 9V battery backup
• Interconnection for up to 12 devices

This 6-pack gives buyers a photoelectric alternative to the ionization alarms in the First Alert and BRK picks. A hidden LED, test button, and silence function support regular checks.

See it on Amazon

Pros

• Photoelectric sensor
• 6-pack
• Interconnected design

Cons

• Different brand from the First Alert and BRK picks
• Compatibility with existing alarms needs confirmation

The Siterlink Hardwired Interconnected Smoke Detectors are the best pick here for buyers who prefer photoelectric smoke detection. The GS562A model uses 120V AC hardwired power with a 9V battery backup and has an alarm louder than 85 dB.

This 6-pack can interconnect up to 12 devices. When one alarm detects smoke, the other connected alarms sound the same signal, while the red LED flashes on the alarm that detected the smoke.

The test button supports a weekly check, and holding it for 2 seconds can silence an alarm when there is no fire hazard. A hidden LED gives a softer visual indicator, with green showing operation and red showing an alarm or warning.

This model is a useful alternative when you want photoelectric sensing instead of the ionization sensors used by the First Alert and BRK smoke-only alarms. Before mixing it with existing alarms, confirm that the wiring and interconnection requirements match.

5

FIRST ALERT BRK SC9120FF Hardwired Smoke: Best for one-room smoke and CO replacement

9.3/10Our score

• Smoke and CO detection
• Electrochemical CO sensor
• Ionization smoke sensor
• 85 decibel siren

This 1-pack is a practical choice when one existing hardwired alarm needs replacement and you want smoke and CO detection in the same unit.

See it on Amazon

Pros

• Combination smoke and CO alarm
• 85 decibel siren
• Battery backup

Cons

• Single unit
• Ionization smoke sensor

The FIRST ALERT BRK SC9120FF is the best fit for replacing one hardwired alarm with combined smoke and CO detection.

It uses an ionization sensor for smoke and an electrochemical sensor for carbon monoxide.

That gives one unit two jobs, which can simplify replacement when an older combination alarm is already in place.

The 1-pack includes one combination alarm, a 9V backup battery, and a user manual.

Its 85 decibel siren and face-mounted indicator lights give you an audible and visual warning, including an indication of whether the detected hazard is smoke or CO.

That visual cue can be helpful because smoke and carbon monoxide need different responses.

A single test and silence button supports regular checks.

The battery drawer lock and mounting bracket lock add tamper resistance, while the hardwired design lets the unit connect with compatible BRK or First Alert detectors.

For care, keep the unit in its intended position, use the test control regularly, and follow the manual for battery changes and cleaning.

Choose this model when one room needs a combination replacement.

For several rooms, the SC9120B-6 provides the same general smoke and CO approach in a larger pack.

How do First Alert hardwired smoke alarms compare with other options?

First Alert and BRK are strongest in this group when you want familiar model families, battery backup, and compatible hardwired interconnection.

Their 9120B and SC9120B models share a similar design language, which can make a mixed replacement plan easier to manage.

Siterlink stands out because its GS562A uses a photoelectric sensor and comes as a 6-pack.

That sensor difference is the main practical split in this group.

The 9120B options focus on smoke detection through ionization sensors.

They suit buyers who want a smoke alarm that is set up for fast flaming fires and who do not need CO sensing in that same unit.

The SC9120 options add electrochemical carbon monoxide sensing, so they can cover smoke and CO in one alarm.

That can reduce the number of separate devices on a ceiling or wall, but it requires thinking about which rooms actually need CO coverage.

In a home with fuel burning appliances, a fireplace, or an attached garage, combination alarms may fit the plan more closely.

In a room far from those sources, a smoke only alarm may be enough.

The 1-pack, 3-pack, and 6-pack sizes also change how you plan the job.

A single unit works for a focused replacement, while a multipack can help you keep the same model across several rooms.

Battery backup is common across these picks, which helps during a power outage.

It does not remove the need for correct hardwired installation, because the alarms still depend on their AC connection for normal operation.

Test and silence controls are also similar on the First Alert and BRK models, with a single button for routine checks.

The Siterlink model uses its own test and silence approach with LED indicators, so the daily routine feels a little different.

That difference is not a major barrier, but it is worth noting if you want every alarm in the home to work the same way.

For buyers comparing brands, our guide to the best Kidde hardwired smoke detector covers another major hardwired alarm family.

If audible guidance matters, see the best smoke detector with voice alert options.

Staying with First Alert and BRK may suit a home that already has compatible alarms and wiring.

Choosing Siterlink may suit a buyer who prefers photoelectric detection and wants a six unit pack.

The right comparison is less about brand loyalty and more about sensor type, pack size, and compatibility with what is already installed.

How many hardwired smoke alarms should you install?

Place smoke alarms on each level and in each bedroom, then use compatible interconnected models where your wiring supports them.

The product information for the First Alert and BRK alarms specifically recommends one on each level and in each bedroom.

That placement rule is a useful starting point because it spreads coverage through the spaces where people sleep and move through the home.

Hallways and living areas on each level can also matter, especially when doors are closed at night.

A 3-pack can cover a smaller home or a partial replacement.

It can work well when you are updating alarms in a few key rooms and leaving the rest of the system for another stage.

For more pack-size options, see our hardwired smoke detector multipacks.

A 6-pack makes more sense when you need alarms across several rooms or want smoke and CO protection in multiple locations.

That larger count can suit a two story home, a home with several bedrooms, or a full refresh of an older system.

It also gives you spare units for areas where an older alarm needs to be replaced sooner.

Count the existing alarm boxes before choosing a pack.

Walk through the home and note each level, each bedroom, and any hallway location that already has an alarm box.

Also check whether the replacement uses the same wiring connector and whether your preferred model can connect to the alarms already installed.

A mismatch there can turn a simple swap into a longer project.

Think about CO placement separately from smoke placement.

Combination alarms may be most useful near fuel burning appliances and sleeping areas, while smoke only alarms can cover other rooms.

That mix can help you avoid buying more CO sensing than you need.

It can also help you keep the alarm style consistent where it matters most.

Plan for testing after installation on every level.

Once each alarm is mounted and powered, test it and make sure connected units respond as expected.

Leave enough access to the test button and battery compartment for regular care.

That access makes weekly checks and battery changes easier over time.

What should you check before installing a hardwired smoke alarm?

Check the existing wiring, model compatibility, mounting position, and battery type before installation.

Hardwired work involves household electrical connections, so follow the product instructions and local requirements.

Start by turning off power at the breaker before you open an existing alarm box.

That step protects you while you check the wiring and prepare the new mounting bracket.

Match the replacement model to the wiring connector in the box.

Some First Alert and BRK models are designed to work with compatible alarms, but not every model connects to every other model.

If you are mixing old and new units, confirm compatibility before you mount anything.

Also check the mounting position against the guidance for the room.

The alarms in this group are meant for ceiling or wall use as directed, and the bracket should sit flat and secure.

Keep the battery compartment accessible after installation.

The models here use battery backup, but the battery does not replace the AC connection.

It keeps the alarm working during a power failure, while the hardwired supply handles normal operation.

Test the alarm after installation and continue regular checks with the test button.

That first test confirms power, sound, and interconnection before you close up the job.

Keep the battery compartment accessible.

The First Alert and BRK models use side-load battery access, while the Siterlink model includes a test and silence button with LED status indicators.

Side load access can make battery changes simpler because you may not need to remove the whole alarm from its bracket.

Still, follow the manual for the exact opening and locking steps.

Dust, insects, and kitchen placement can affect nuisance alarms, so keep the sensor area clean and follow the placement limits in the instructions.

Replace the backup battery when the low battery warning sounds, even if the alarm still has AC power.

For a full comparison of power choices, read our guide to hardwired vs battery smoke detectors.

It explains when a wired setup may suit your home and when a battery-only alarm may be simpler.

What is the best First Alert smoke detector hardwired choice?

Choose the BRK First Alert 9120BFF/SMI100-AC for a standard smoke-only replacement with ionization detection, battery backup, and compatible interconnection.

It is the cleanest pick when one existing hardwired smoke alarm needs a direct upgrade.

Choose the First Alert BRK SC9120B-6 when you need smoke and CO detection across several rooms.

That 6-pack suits a larger home or a planned refresh of several combination alarms.

It also helps when you want the same two hazard coverage in each location.

Pick the 9120B 3-pack for a smaller multi-room smoke upgrade.

That size fits a partial replacement where three smoke only alarms need the same model.

Choose Siterlink if photoelectric sensing and a 6-pack matter more than staying within the First Alert and BRK model families.

The GS562A gives you a different sensor approach with a hidden LED and a test and silence button.

If one unit needs replacement and you want both hazard types, the FIRST ALERT BRK SC9120FF is the focused choice.

It pairs ionization smoke detection with electrochemical CO sensing in a single hardwired alarm.

Think about the room before you buy.

A bedroom, hallway, or living area may need different coverage than a room near a furnace, water heater, or fireplace.

That room by room plan helps you choose the right pack size and sensor mix.

Check the exact model and wiring compatibility before connecting it to an existing alarm system.

Confirm the connector, the interconnection limits, and the mounting hardware before you start.

Then test each alarm after installation and keep the test button routine in place.

That simple check helps you know the system is ready for daily use.

Our top 3 picks at a glance

1. 1
   Best for standard smoke protection

   BRK First Alert 9120BFF/ SMI100-AC Smoke Detector

   9.7/10 our score

   See it on Amazon
2. 2
   Best for whole-home smoke and CO coverage

   First Alert BRK SC9120B-6 Hardwired Smoke

   9.7/10 our score

   See it on Amazon
3. 3
   Best for multi-room smoke upgrades

   First Alert 9120B / SMI100-AC Smoke Detector

   9.7/10 our score

   See it on Amazon

Frequently asked questions

What is the best First Alert smoke detector hardwired option?

The BRK First Alert 9120BFF/SMI100-AC is the best match for standard hardwired smoke protection in this group. It has an ionization sensor, a 120V AC connection, a 9V battery backup, an 85 decibel alarm, and compatible BRK and First Alert interconnection.

Choose an SC9120 model instead when carbon monoxide detection is also part of your plan.

Are First Alert and BRK hardwired smoke alarms compatible?

Some First Alert and BRK hardwired alarms are designed to connect with compatible alarms from both brands. Compatibility depends on the specific model and wiring setup, so match the model instructions before combining alarms.

Do not assume every First Alert or BRK alarm can interconnect with every other model.

What is the difference between the First Alert 9120B and SC9120B?

The 9120B models in this roundup are smoke alarms with ionization sensors. The SC9120B models add carbon monoxide detection through an electrochemical sensor, so they cover two hazards in one hardwired unit.

Read our First Alert SC9120B vs 9120B comparison for the model differences.

Should you choose ionization or photoelectric smoke detection?

Ionization alarms in this roundup are designed to detect smoke from fast flaming fires. The Siterlink GS562A uses a photoelectric sensor, giving you a different detection approach.

Your local code, existing wiring, and the alarm types already installed in your home should guide the choice.