9 Best First Alert Smoke and Carbon Monoxide Alarms (November 2026)

The best First Alert smoke and carbon monoxide alarms include the First Alert Hardwire Combination Smoke & Carbon for whole-home hardwired coverage, the Kidde Smoke & Carbon Monoxide Detector for voice alerts, and the First Alert Plug in Carbon Monoxide Alarm for visible CO readings.

On this page (16 sections)

1. Which First Alert smoke carbon monoxide alarm is best?
2. How we chose these smoke and CO alarms
3. First Alert Hardwire Combination Smoke & Carbon: Best for whole-home hardwired coverage
4. Kidde Smoke & Carbon Monoxide Detector: Best for voice alerts
5. First Alert Plug in Carbon Monoxide Alarm: Best for visible CO readings
6. X-Sense Smoke & Carbon Monoxide Alarm: Best for no-rewire installation
7. BRK SC9120B Smoke and Carbon Monoxide Alarm: Best for BRK replacement installs
8. First Alert SC-9120B Hardwired Smoke and Carbon: Best for a 2-alarm hardwired update
9. First Alert BRK SC-9120B xrHsEW: Best for larger SC9120B replacements
10. First Alert BRK CO5120BN: Best for hardwired CO-only coverage
11. First Alert 1039734 Fat Plug-in Carbon Monoxide: Best for simple plug-in CO coverage
12. How do you choose between hardwired and battery-backed alarms?
13. Do First Alert combination alarms detect smoke and carbon monoxide?
14. What should you check before installing a First Alert smoke and CO alarm?
15. How should you care for smoke and CO alarms?
16. Verdict: which First Alert smoke carbon monoxide alarm should you buy?

The best First Alert smoke carbon monoxide alarm for most homes is the First Alert Hardwire Combination Smoke & Carbon, because it combines smoke and CO detection, battery backup, and compatible First Alert and BRK interconnection. That mix suits a home that wants coordinated warnings from alarms in more than one room.

Choose a plug-in model for simpler CO monitoring, or a BRK alarm when you are matching an existing hardwired system. The right pick depends less on the name on the box and more on the wiring, sensor type, and alarm family already in place.

A combination alarm can save wall space because one unit watches for two hazards. It also means a smoke warning and a carbon monoxide warning may sound from the same device, so the indicators and instructions matter.

We compared the First Alert and BRK options here by sensor type, power source, battery backup, alarm coverage, pack size and system compatibility. We also looked at how each design fits daily use, from testing and silencing to replacing a backup battery.

Our score weighs specs, features and buyer feedback against what you are shopping for. A high score does not mean a model fits every home, because a plug-in CO alarm and a hardwired combination alarm solve different problems.

Hardwired alarms suit replacement projects and homes with an existing alarm network. Plug-in and battery models suit renters, small spaces, or rooms where adding alarm wiring is not practical.

Pack size also changes the value of a purchase. A multi-pack can cover several rooms at once, while a single unit may be enough for one replacement or an added CO location.

Battery backup is a key detail for hardwired models. It helps maintain monitoring during a power outage, but it does not remove the need to test the alarm and follow replacement guidance.

If you need a basic explanation first, read what is a smoke alarm before choosing between a smoke-only, CO-only or combination alarm. That background helps you match the hazard, the sensor, and the installation method.

The sections below separate the picks by job instead of expecting one alarm to do everything. Read the trade-off notes before you order, especially where compatibility or CO-only coverage changes what the product can do.

Our picks at a glance

1. 1
   Best for whole-home hardwired coverage

   First Alert Hardwire Combination Smoke & Carbon

   9.7/10 our score

   See it on Amazon
2. 2
   Best for voice alerts

   Kidde Smoke & Carbon Monoxide Detector

   9.6/10 our score

   See it on Amazon
3. 3
   Best for visible CO readings

   First Alert Plug in Carbon Monoxide Alarm

   9.5/10 our score

   See it on Amazon

4. 4

   X-Sense Smoke & Carbon Monoxide Alarm

   Best for no-rewire installation
   Check it
5. 5

   BRK SC9120B Smoke and Carbon Monoxide Alarm

   Best for BRK replacement installs
   Check it
6. 6

   First Alert SC-9120B Hardwired Smoke and Carbon

   Best for a 2-alarm hardwired update
   Check it
7. 7

   First Alert BRK SC-9120B xrHsEW Hardwired Smoke

   Best for larger SC9120B replacements
   Check it
8. 8

   First Alert BRK CO5120BN Hardwire Carbon Monoxide

   Best for hardwired CO-only coverage
   Check it
9. 9

   First Alert 1039734 Fat Plug-in Carbon Monoxide

   Best for simple plug-in CO coverage
   Check it

Which First Alert smoke carbon monoxide alarm is best?

The best overall choice is the First Alert Hardwire Combination Smoke & Carbon, while the First Alert Plug in Carbon Monoxide Alarm is better when you need a visible CO reading at an outlet. Your existing wiring and alarm brand should guide the final choice.

The top pick is a 6-count hardwired combination alarm with a 9V battery backup. It can interconnect with most First Alert and BRK alarms, so compatible alarms can sound together when one detects a hazard.

The Kidde model is the strongest alternative for buyers who want spoken warnings. It is a hardwired combination alarm with voice alerts for fire, carbon monoxide and low battery, plus a 2-AA battery backup.

The X-Sense SC06 is the most convenient option for homes where rewiring is not practical. It uses a 10-year built-in lithium battery, but it is a standalone model without wireless interconnection.

How we chose these smoke and CO alarms

We checked each product's stated alarm coverage, sensor type, power source, backup power, pack size and connection method. We also considered how each option fits a real installation, such as replacing several hardwired alarms or adding CO monitoring near an outlet.

For combination alarms, smoke and carbon monoxide coverage matters more than a single extra feature. A hardwired model may suit an existing alarm network, while a sealed-battery model may make installation easier in a home without alarm wiring.

For CO-only alarms, we looked for details that affect daily use. A digital display shows more information than a basic alarm, while a test and silence button gives you a direct way to check or quiet the unit when appropriate.

Smoke detector vs carbon monoxide detector explains why the two hazards need different detection and why a CO-only alarm cannot replace a smoke alarm.

First Alert Hardwire Combination Smoke & Carbon: Best for whole-home hardwired coverage

1

First Alert Hardwire Combination Smoke & Carbon: Best for whole-home hardwired coverage

9.7/10Our score

• Smoke and CO detection
• Battery backup
• Interconnects with most First Alert and BRK alarms
• 6-count pack

This 6-count hardwired combination alarm suits homes that need coordinated smoke and CO coverage across several rooms. Battery backup continues protection during power outages.

See it on Amazon

Pros

• 6-count pack
• Battery backup
• Compatible First Alert and BRK alarm interconnection

Cons

• Requires hardwired installation
• Ionization smoke sensor may not suit every buyer

The First Alert Hardwire Combination Smoke & Carbon is the best match for a larger home that needs several coordinated alarms. Its 6-count pack gives you multiple combination units for a planned installation across bedrooms, hallways and other suitable locations.

The alarm uses First Alert's Precision Detection technology and an ionization sensor. First Alert says the sensing system helps reduce cooking nuisance alarms while providing early warning.

Treat that as a design claim, and still follow the placement and care instructions.

A 9V battery backup keeps the alarm operating during a power outage. The unit also has a Perfect Mount bracket, a latching alarm indicator and a stated size of 5.6 in D x 5.6 in W x 1.9 in H.

Interconnection is the main reason to choose this model over a standalone alarm. It works with most First Alert and BRK alarms, but check the existing system before connecting units from different product families.

Choose this pick when you want smoke and CO detection in one hardwired alarm across several rooms. Its main trade-off is that installation depends on suitable wiring and compatible alarms.

Kidde Smoke & Carbon Monoxide Detector: Best for voice alerts

2

Kidde Smoke & Carbon Monoxide Detector: Best for voice alerts

9.6/10Our score

• Hardwired smoke and CO detection
• Voice alerts
• 2-AA battery backup
• Pack of 2

The Kidde combination alarm adds spoken warnings for fire, carbon monoxide and low battery. It fits homes already using compatible Kidde devices and hardwired connections.

See it on Amazon

Pros

• Voice alert messages
• Hush feature
• Interconnects with up to 24 Kidde devices

Cons

• Kidde system compatibility matters
• Hardwired installation required

The Kidde Smoke & Carbon Monoxide Detector is best for households that want an audible voice message to identify the hazard. It says “Fire,” “Warning!

Carbon Monoxide!” or “Low Battery!” instead of relying only on a tone.

This is a hardwired combination alarm with a 120VAC power source and 2-AA battery backup. Its ionization smoke sensor detects invisible fire particles, and the alarm uses an 85 dB warning.

The Test-Hush feature silences the unit for about 9 minutes. A tamper-resistant design helps deter removal, and the alarm can connect with up to 24 Kidde devices, with limits on how many can initiate an alarm.

The pack contains 2 alarms. Choose it when you are building or extending a compatible Kidde system and want voice alerts.

The main trade-off is that it is not a First Alert or BRK replacement for every existing wired setup.

For a wider look at combination alarms, compare it with the best combination smoke and CO detectors.

First Alert Plug in Carbon Monoxide Alarm: Best for visible CO readings

3

First Alert Plug in Carbon Monoxide Alarm: Best for visible CO readings

9.5/10Our score

• Digital display
• Electrochemical CO sensor
• AA battery backup
• Peak CO level feature

This plug-in alarm is designed for carbon monoxide monitoring rather than smoke detection. Its digital display shows CO and power information at a glance.

See it on Amazon

Pros

• Digital display
• Peak level memory
• Works with a standard outlet

Cons

• CO-only protection
• Battery backup is not intended for extended standalone use

The First Alert Plug in Carbon Monoxide Alarm is the best choice here when you want CO monitoring with a digital display. It plugs into a standard outlet and shows current carbon monoxide and power information.

Its electrochemical CO sensor includes a peak-level feature that displays the highest measured concentration. An 85 dB alarm sounds when carbon monoxide reaches dangerous levels, and the unit has a test and silence button.

The alarm uses corded electric power with AA battery backup. The battery supports monitoring during a power failure, but it is not intended to run the alarm for an extended period without AC power.

This is a CO-only unit, so it does not replace smoke alarms. First Alert recommends placing CO alarms on each level and in each bedroom for complete coverage.

Choose it for an outlet near a sleeping area or another location where a visible reading is useful. Skip it if you need smoke detection in the same device or if you are replacing a hardwired alarm network.

X-Sense Smoke & Carbon Monoxide Alarm: Best for no-rewire installation

4

X-Sense Smoke & Carbon Monoxide Alarm: Best for no-rewire installation

9.4/10Our score

• Photoelectric smoke and electrochemical CO sensors
• 10-year built-in lithium battery
• Wall or ceiling mounting
• 5-count pack

The X-Sense SC06 suits homes where rewiring is not practical. Its sealed battery and included mounting hardware support a simple standalone installation.

See it on Amazon

Pros

• 10-year built-in battery
• Dual-sensor detection
• 5-count pack

Cons

• No wireless interconnection
• Not a First Alert product

The X-Sense Smoke & Carbon Monoxide Alarm is the best fit when you want combination protection without rewiring. The 5-count pack uses wall or ceiling mounting with included brackets, screws and anchor plugs.

The SC06 combines a photoelectric smoke sensor with an electrochemical CO sensor. X-Sense says the dual-sensor design responds to smoldering fires, reduces cooking-related false alarms and detects carbon monoxide.

A built-in lithium battery keeps each alarm powered for 10 years. That removes routine battery swaps, but the battery is sealed into the unit and the alarm is not designed to join a wireless network.

This is a standalone model. It does not support wireless interconnection, Wi-Fi or a base station connection, so every alarm operates independently.

Choose it when a simple installation matters more than interconnection. If you want to compare more X-Sense options, see the best X-Sense combination smoke and CO detector guide.

BRK SC9120B Smoke and Carbon Monoxide Alarm: Best for BRK replacement installs

5

BRK SC9120B Smoke and Carbon Monoxide Alarm: Best for BRK replacement installs

9.1/10Our score

• Dual ionization smoke detection
• CO sensor
• 9V battery
• Interconnects with BRK and First Alert hardwired alarms

The BRK SC9120B is a practical replacement choice for compatible BRK or First Alert alarm systems. Separate smoke and CO indicators help identify the warning type.

See it on Amazon

Pros

• BRK and First Alert interconnection
• Separate smoke and CO indicators
• Test and silence button

Cons

• Single-unit pack
• Ionization smoke sensor

The BRK SC9120B is the best match for replacing one compatible BRK or First Alert hardwired alarm. It combines ionization smoke detection with a carbon monoxide sensor and uses a 9V battery for backup use.

A single test and silence button keeps routine checks simple. Separate smoke and CO latching indicators help show which hazard triggered the alarm, which can save time when several alarms sound at once.

The universal mounting bracket supports a replacement installation in many existing locations. That helps when the old alarm and the new alarm use the same general mounting approach, but the exact fit should still be checked.

The SC9120B can interconnect with BRK and First Alert hardwired smoke and carbon monoxide alarms. It can connect with up to 12 smoke alarms and 6 compatible devices within the stated system limits.

Choose it when the model matches your current wiring and alarm network. It suits a one-for-one swap better than a full home refresh, because the purchase covers a single unit.

Its main limitation is that replacing several alarms may require multiple units or a multi-pack alternative. For a larger project, compare pack options and confirm that every new alarm matches the existing system.

First Alert SC-9120B Hardwired Smoke and Carbon: Best for a 2-alarm hardwired update

6

First Alert SC-9120B Hardwired Smoke and Carbon: Best for a 2-alarm hardwired update

8.7/10Our score

• Hardwired smoke and CO detection
• Battery backup
• 2-unit pack
• Side-load battery compartment

This 2-unit SC-9120B pack fits a smaller replacement project where compatible hardwired alarms already exist. Battery backup helps maintain monitoring during outages.

See it on Amazon

Pros

• 2-unit pack
• Battery backup
• Compatible BRK and First Alert connections

Cons

• Compatibility should be checked before installation
• Hardwired installation required

The First Alert SC-9120B Hardwired Smoke and Carbon is a practical choice for a smaller two-alarm replacement project. The pack contains 2 units, each with hardwired power and battery backup for continued monitoring during an outage.

The alarm uses electrochemical CO sensing and ionization smoke sensing. Lights indicate whether the alarm concerns smoke or carbon monoxide, while the single test and silence button keeps operation familiar.

It can connect with compatible BRK or First Alert CO smoke detectors in a single-family residence. That makes it a fit for homes where the installed alarms already use a compatible hardwired network.

The side-load battery compartment makes battery access easier after the alarm is installed. You still need to test the unit, listen for low-battery signals, and replace backup power as directed.

Choose this pack when two compatible hardwired combination alarms need replacement at the same time. It can create a consistent setup across two locations without buying separate single units.

Before buying, match the model and connection requirements with the alarms already mounted in your home. Do not assume that every First Alert or BRK alarm will interconnect with this model.

For more hardwired options, read best combination smoke co detector hardwired.

First Alert BRK SC-9120B xrHsEW: Best for larger SC9120B replacements

7

First Alert BRK SC-9120B xrHsEW Hardwired Smoke: Best for larger SC9120B replacements

8.5/10Our score

• Hardwired smoke and CO detection
• Battery backup
• 4-unit pack
• Latching alarm indicator

The 4-unit pack makes sense when several compatible alarms need replacement at once. Its latching indicator can identify the alarm that initiated a warning after conditions settle.

See it on Amazon

Pros

• 4-unit pack
• Battery backup
• Latching alarm indicator

Cons

• Hardwired installation required
• Compatibility should be confirmed first

The First Alert BRK SC-9120B xrHsEW is best for replacing several compatible alarms at once. Its 4-unit pack gives you a consistent SC-9120B setup for a larger hardwired installation.

The combination alarm uses electrochemical CO sensing and ionization smoke sensing. Indicator lights help distinguish a smoke warning from a carbon monoxide warning when the alarm sounds.

A 9V backup battery allows the alarm to function during a power outage. That backup role matters most in the hours when normal power is unavailable and the home still needs monitoring.

The latching alarm indicator identifies the unit that initiated an alarm even after the triggering condition has ended. That can help you find the source room after the sound has stopped or conditions have changed.

Tamper-resistant and universal mounting brackets support a secure replacement. They also help keep the alarm in place, which matters in homes where alarms can be knocked or removed during routine care.

Choose this model when your existing system accepts compatible First Alert or BRK SC-9120B alarms. Its trade-off is that hardwired connection and system compatibility need to be confirmed before installation.

First Alert BRK CO5120BN: Best for hardwired CO-only coverage

8

First Alert BRK CO5120BN Hardwire Carbon Monoxide: Best for hardwired CO-only coverage

8.3/10Our score

• Electrochemical CO sensor
• Battery backup
• 2-count pack
• Hardwired design

This 2-count alarm focuses on carbon monoxide rather than smoke detection. It suits a hardwired setup that needs added CO coverage alongside separate smoke alarms.

See it on Amazon

Pros

• CO-only focus
• Electrochemical sensor
• 2-count pack

Cons

• Does not detect smoke
• Hardwired installation required

The First Alert BRK CO5120BN is the right choice when you need carbon monoxide detection without combination smoke sensing. Its electrochemical sensor focuses on CO, and the 2-count pack helps cover more than one location.

This model is a hardwired carbon monoxide alarm with battery backup. It can work alongside separate smoke alarms when your home already has smoke detection in place but needs added CO coverage.

A CO-only design can suit a system where smoke and CO alarms have separate jobs. That may make placement simpler, because each alarm is chosen for one hazard rather than sharing a single housing.

Choose it for a hardwired system where smoke alarms and CO alarms serve separate roles. It can fit a plan that adds CO monitoring near sleeping areas or fuel-burning appliances.

Do not use it as the only alarm in a room where smoke detection is also required. A CO alarm cannot warn you about smoke from a fire, and a smoke alarm cannot replace CO detection.

The main advantage is focused CO coverage in a two-unit pack. The main limitation is equally clear: this model does not detect smoke.

First Alert 1039734 Fat Plug-in Carbon Monoxide: Best for simple plug-in CO coverage

9

First Alert 1039734 Fat Plug-in Carbon Monoxide: Best for simple plug-in CO coverage

8.0/10Our score

• Electrochemical CO sensor
• Battery backup
• 85 dB alarm
• Test and silence button

This plug-in alarm offers a simple way to monitor carbon monoxide in a home, office or other space. It is a CO-only alarm with battery backup.

See it on Amazon

Pros

• Simple plug-in design
• Electrochemical sensor
• Battery backup

Cons

• Does not detect smoke
• Large stated dimensions need outlet-space planning

The First Alert 1039734 Fat Plug-in Carbon Monoxide Alarm suits buyers who want a straightforward plug-in CO detector with battery backup. It uses an electrochemical sensor and has an 85 dB alarm for audible warning.

A test and silence button keeps the controls simple. That simple layout can suit a busy household, because there is less to learn before testing the alarm or responding to a warning.

The product includes the detector, hardware, battery and owner's manual. Keeping the manual with the alarm helps you follow placement, testing, and replacement instructions for the exact model.

Its stated dimensions are 8.50 x 6.75 x 2.25 in. Those dimensions should be checked against the outlet and nearby furniture before you buy, so the alarm does not block other plugs.

This is a CO-only alarm for a home, office or other space with a standard electrical socket. It does not detect smoke, so pair it with appropriate smoke alarms when you need both types of protection.

Choose it when simple installation matters more than a digital display or hardwired interconnection. Plan the outlet space carefully because the stated dimensions are larger than some compact plug-in alarms.

How do you choose between hardwired and battery-backed alarms?

Choose a hardwired alarm when your home already has compatible wiring or you are replacing an interconnected system. Choose a sealed-battery standalone model when you want to mount alarms without rewiring.

Hardwired models can coordinate several alarms when the devices are compatible. That can make a warning easier to hear in another part of the home, but the wiring and alarm family must match.

Battery backup matters because a corded alarm may lose normal power during an outage. The First Alert Hardwire Combination Smoke & Carbon, Kidde model and SC-9120B models all include backup power in their stated designs.

The X-Sense SC06 takes a different approach with a built-in 10-year lithium battery. It avoids battery changes, but it does not provide wireless interconnection.

Do First Alert combination alarms detect smoke and carbon monoxide?

Yes, the combination models in this roundup detect both smoke and carbon monoxide, but the sensor types differ. Smoke sensors include ionization or photoelectric designs, while the CO sensors listed here are electrochemical.

The First Alert Hardwire Combination Smoke & Carbon uses an ionization sensor for smoke. The Kidde detector also uses ionization smoke sensing, while the X-Sense SC06 combines photoelectric smoke sensing with electrochemical CO sensing.

The BRK SC9120B and First Alert SC-9120B models use ionization smoke sensing and electrochemical CO sensing. Their indicators help separate smoke warnings from CO warnings, which can guide your next step.

A combination alarm reduces the number of devices you need to mount. It also means one housing, one power source, and one set of indicators must cover two different hazards.

Sensor choice affects the kinds of particles or gases the alarm is designed to detect. Ionization and photoelectric smoke sensors respond in different ways, so the best match depends on the fire conditions you want to cover.

Electrochemical CO sensing is the CO technology used across the CO alarms in this guide. A CO-only model, such as the First Alert Plug in Carbon Monoxide Alarm or CO5120BN, cannot replace a smoke alarm.

That distinction matters when you plan coverage for a room. If a space needs both smoke and CO protection, you need either a combination alarm or separate alarms for each hazard.

Placement also matters because different hazards move through a home in different ways. Read the instructions for placement, testing, silence functions and replacement timing for the exact alarm you install.

What should you check before installing a First Alert smoke and CO alarm?

Check the existing power connection, alarm family, interconnection rules, mounting location and backup battery before installation. A replacement alarm must fit both the physical location and the electrical system.

For a hardwired replacement, identify the current alarm model and confirm that the new unit supports the same compatible connection. Do not assume that every alarm with the First Alert or BRK name can interconnect with every other model.

For plug-in alarms, make sure the outlet has power and that the alarm does not block nearby plugs. For battery-powered models, choose a location where the alarm can be mounted securely and tested regularly.

Follow local fire-safety guidance and the instructions for the exact alarm. The alarm's manufacture date, replacement signal and battery instructions also matter over the life of the unit.

How should you care for smoke and CO alarms?

Test each alarm according to its instructions, keep the sensing openings clear, and respond to low-battery or end-of-life signals. Never remove a battery or disable an alarm to stop nuisance warnings.

Cooking can trigger some smoke alarms, so placement away from cooking fumes matters. The First Alert Hardwire Combination Smoke & Carbon uses Precision Detection technology that First Alert says reduces cooking nuisance alarms, but good placement is still necessary.

Keep track of which alarm is installed in each room, especially in an interconnected system. A latching indicator can help identify the alarm that initiated a warning after the sound stops.

Replace an alarm when its instructions call for replacement or when it signals end of life. If a CO alarm sounds, move to fresh air and follow local emergency guidance rather than treating the warning as a routine test.

Verdict: which First Alert smoke carbon monoxide alarm should you buy?

The First Alert Hardwire Combination Smoke & Carbon is the best overall pick for a compatible hardwired home because it offers smoke and CO detection, battery backup, interconnection and a 6-count pack. Choose the Kidde model if spoken warnings matter most.

Pick the First Alert Plug in Carbon Monoxide Alarm for visible CO readings at a standard outlet. Pick the X-Sense SC06 when you need no-rewire installation and can accept standalone alarms.

For a BRK or First Alert replacement system, compare the SC9120B packs with your existing alarm model before ordering. If you only need CO detection, the CO5120BN is the focused hardwired option, while the 1039734 is the simpler plug-in choice.

For more placement and hazard guidance, continue with the best carbon monoxide detector for travel guide when you need portable CO coverage outside the home.

Our top 3 picks at a glance

1. 1
   Best for whole-home hardwired coverage

   First Alert Hardwire Combination Smoke & Carbon

   9.7/10 our score

   See it on Amazon
2. 2
   Best for voice alerts

   Kidde Smoke & Carbon Monoxide Detector

   9.6/10 our score

   See it on Amazon
3. 3
   Best for visible CO readings

   First Alert Plug in Carbon Monoxide Alarm

   9.5/10 our score

   See it on Amazon

Frequently asked questions

What is the best First Alert smoke carbon monoxide alarm?

The First Alert Hardwire Combination Smoke & Carbon is the strongest overall choice here because it combines smoke and CO detection, battery backup, a 6-count pack and compatible First Alert and BRK interconnection. Choose a plug-in CO alarm when you only need carbon monoxide monitoring.

Are First Alert and BRK smoke and CO alarms compatible?

Some First Alert and BRK hardwired alarms can interconnect, but compatibility depends on the alarm models and the existing system. The SC9120B models here are described as compatible with BRK and First Alert hardwired alarms.

Check the exact model before replacing an installed unit.

Should you buy a hardwired or plug-in CO alarm?

Choose a hardwired alarm when you are replacing an existing wired system or planning a wired installation. Choose a plug-in model when you want simpler placement at a standard outlet.

Plug-in CO alarms here do not replace smoke detection, so use separate smoke alarms where needed.

What does a combination smoke and CO alarm detect?

A combination alarm detects both smoke from a fire and carbon monoxide. The products use different sensor types, including ionization or photoelectric smoke sensing and electrochemical CO sensing.

A CO-only alarm, such as the CO5120BN, does not detect smoke.

How many smoke and CO alarms should a home have?

Place alarms according to local fire-safety guidance and the instructions for your home. First Alert recommends CO alarms on each level and in each bedroom for its CO615 model.

Check placement, interconnection and replacement requirements before installation.