Top 10 Best Carbon Monoxide Detectors (Reviews & Buyers’ Guide 2021)

We recommend products and services based on unbiased research from our editorial team. We may receive compensation if you click on a link. Last updated on August 19, 2021

Kidde Nighthawk Plug-In Carbon Monoxide Alarm Detector KN-COPP-3
  • Best carbon monoxide detector of 2021
  • Digital display shows CO levels from 30 to 999 ppm
  • Peak level button records the highest CO level since it was last reset or unplugged
Our Rating: 5.0/5.0
Check Price
#1-Top Expert Choice
First Alert Plug-In Carbon Monoxide Detector CO605
  • One of the most affordable of the best carbon monoxide detectors
  • With battery backup for continuous operation during power outages
  • Simple to use with a single test and silence button
Our Rating: 4.9/5.0
Check Price
#2-Premium Choice
Kidde Combination Smoke and Carbon Monoxide Alarm KN-COSM-BA
  • Smoke detector and carbon monoxide alarm in one
  • Battery-powered unit with a front-loading battery door
  • Voice alarm in addition to standard beeps and LED light
Our Rating: 4.8/5.0
Check Price
#3
Google Nest Protect Alarm-Smoke Carbon Monoxide Detector S3003LWES
  • Phone alerts to warn you of any alarm changes when you're away
  • Light ring glows in 5 colors, including “Nightly Promise” green
  • Electrochemical CO sensor and split-spectrum sensor to detect smoke from fast- and slow-burning fires
Our Rating: 4.7/5.0
Check Price
#4
First Alert Dual-Power Carbon Monoxide Detector CO615
  • Digital backlit LED display reads the current CO level and peak CO level since it was last reset
  • Works with standard electrical outlets; has a battery backup for power outages
  • Audible and visual alerts signal low batteries
Our Rating: 4.6/5.0
Check Price
#5
First Alert Carbon Monoxide Detector CO400
  • Cheapest of the best carbon monoxide detectors
  • Battery-powered construction offers ease of installation
  • Electrochemical sensor lasts for up to 5 years
Our Rating: 4.5/5.0
Check Price
#6
X-Sense Smoke and Carbon Monoxide Alarm SC01
  • Built-in lithium battery provides 10 years of continuous power; alarm has a 10-year lifespan
  • Equipped with electrochemical and photoelectric sensors for smoke and CO detection
  • Backlit LCD indicates CO levels between 30 to 999 ppm
Our Rating: 4.4/5.0
Check Price
#7
Kidde Carbon Monoxide Detector KN-COP-IC
  • Voice alert, standard alarm, and LED light
  • Digital display shows the current CO level and the peak CO level since it was last reset
  • Includes an adjustable mounting bracket and wiring harness for easy installation
Our Rating: 4.3/5.0
Check Price
#8
X-Sense Carbon Monoxide Detector CD07
  • 10-year sealed lithium battery enclosed in a fire-retardant ABS/PC plastic frame
  • LED indicator glows in 3 colors to indicate alarm, active, and low battery statuses
  • Large LCD shows CO levels, updates CO reading every 10 seconds, and records peak CO level
Our Rating: 4.2/5.0
Check Price
#9
First Alert Onelink Safe & Sound Smart Smoke and Carbon Monoxide Detector
  • Built-in Alexa Voice Services, high-end speakers, and noise-cancelling microphones for hands-free control and complete access to Amazon Echo features
  • Compatible with Apple HomeKit, Apple Onelink Home app, and AirPlay 2
  • Nightlight feature with autobrightness; sounds an 85-decibel standard alarm, voice alarm, and mobile notifications once it senses dangerous smoke or CO levels
Our Rating: 4.1/5.0
Check Price
#10

View the Best Carbon Monoxide Detectors in the Market Below:

1. Kidde Nighthawk Plug-In Carbon Monoxide Alarm Detector KN-COPP-3

Featuring an accurate digital display and an easy-to-install-and-use design, it’s unsurprising that the Kidde Nighthawk Plug-In Carbon Monoxide Alarm Detector KN-COPP-3 ranks first on the list of the best carbon monoxide detectors of 2021.

What users love most about this unit is that it has accurately detected the carbon monoxide level in their rooms. Since its digital reading shows CO levels from 30 to 999 parts per million (ppm), you can easily find out if you need to call in a technician and get some fresh air. Apart from that, it records the peak CO level since the detector was last reset.

Of course, you don’t need to manually check its digital display every now and then. This Kidde carbon monoxide detector emits four 85-decibel beats every five seconds when it detects unhealthy CO levels. It also has a blinking dot to let you know that it’s working and refreshes every 15 seconds to check for any alarming changes.

With the CO detector’s 6-foot extension cord, figuring out where to mount it won’t be a problem. And during power outages, you can rest assured that this UL-listed Kidde carbon monoxide detector, along with its 9-volt battery backup, will still protect you and others from CO poisoning.

Includes Kidde KN-COPP-3 Nighthawk carbon monoxide alarm, 9-volt battery, mounting hardware, and user manual
Sensor type Electrochemical
Power source Corded electric and battery backup
Voltage 120 volts
Alarm noise level 85 decibels
Material ABS plastic
Color White
Dimensions (L x W x H) 3.75 x 1.75 x 6.06 inches
Weight 1.06 pounds
Lifespan 7 years
Warranty 5-year limited warranty
2. First Alert Plug-In Carbon Monoxide Detector CO605

While it’s one of the most affordable carbon monoxide detectors on the market, don’t let the price of the First Alert Plug-In Carbon Monoxide Detector CO605 fool you. With its simple yet effective design, users report that it has already saved their lives.

This unit features a carbon monoxide sensor using advanced electrochemical technology. What this sensor does is that it accurately identifies carbon monoxide no matter where the detector is placed in the room. It’s the perfect CO detector for spacious office spaces and rooms—which is why it comes high up on this list of the best carbon monoxide detectors.

Designed to be plugged into any standard outlet, finding the best location for this commercial carbon monoxide detector will just be a breeze. It even comes with a battery backup, so you can have peace of mind knowing that it’ll still keep you safe from CO poisoning during power outages. Plus, it has a single test and silence button, so you can turn the alarm off with just a press of the button.

Here’s a glimpse of how it works: four beeps and a pause means that it has detected carbon monoxide, one beep every minute means that its batteries need to be replaced, and 5 beeps every minute signals that the whole unit needs to be replaced. And when the CO concentration reaches dangerous levels, it sounds a loud 85-decibel alarm, warning everyone in your home or on your office floor to get out of the building.

With a UL certification, this First Alert carbon monoxide detector has already undergone rigorous testing and passed the highest safety standards. Combine all these features with its fairly low price, and you can keep yourself and others safe without shelling out too much cash.

Includes First Alert CO605 plug-in carbon monoxide detector, 9-volt battery, and user manual
Sensor type Electrochemical
Power source Corded electric and battery backup
Voltage 120 volts
Alarm noise level 85 decibels
Material Plastic
Color White
Dimensions (L x W x H) 3.4 x 1.38 x 5 inches
Weight 11.36 ounces
Lifespan 7 to 10 years
Warranty 7-year limited warranty
3. Kidde Combination Smoke and Carbon Monoxide Alarm KN-COSM-BA

Need both a smoke detector and a carbon monoxide alarm? Have the best of both worlds at the price of one with the Kidde Combination Smoke and Carbon Monoxide Alarm KN-COSM-BA. While this alarm comes at a pretty affordable price, it doesn’t sacrifice quality over affordability.

This Kidde smoke and carbon monoxide alarm offers a one-of-a-kind feature: a voice alarm. What it does is that it beeps four times and announces “Warning! Carbon Monoxide!” when it detects 100 ppm of CO and for smoke, it generates a loud “Fire!,” flashes the red LED, and beeps thrice. It’s like your best friend helpfully screaming at 85 decibels during emergencies—users happily report that it has saved their lives.

Because this Kidde smoke and carbon monoxide alarm is powered by batteries, it’s easy to mount wherever you like. It also comes with a front-loading battery door, letting you easily replace the batteries without having to dismount the alarm. Plus, it announces “low battery” followed by an alarm chirp so that you’ll know once the batteries need to be replaced.

With a voice announcement system combined with the features of both smoke and CO alarms, this Kidde detector is easily one of the best carbon monoxide detectors of 2021.

Includes Kidde KN-COSM-BA combination smoke and carbon monoxide alarm and 3 AA batteries
Sensor type Ionization sensor for smoke, electrochemical sensor for CO
Power source Battery-powered
Voltage 4.5 volts
Alarm noise level 85 decibels
Color White
Dimensions (DIA x W) 5.75 x 1.7 inches
Weight 12.8 ounces
Lifespan 10 years
Warranty 10-year limited warranty
4. Google Nest Protect Alarm-Smoke Carbon Monoxide Detector S3003LWES

If there’s a smart carbon monoxide detector with state-of-the-art features out there, it’s surely one that’s made by Google. Like a CO detector from the future, the Google Nest Protect Alarm-Smoke Carbon Monoxide Detector S3003LWES is the best carbon monoxide detector designed for the modern homeowner in mind.

Even if you’re not at home, the office, or wherever you’re planning to install this alarm, you’ll still have a way of receiving alerts. This Google Nest Protect detector can send a message to your phone when the alarm goes off or if its batteries are running low. What’s more, you can hush the alarm using the Google Nest app’s silence feature.

Apart from the ability to control virtually everything with your phone, the Google Nest Protector offers other features that can’t be found in other CO detectors. It gives you a “Nightly Promise” or emits a green glow to let you know that it has tested itself and its batteries. Besides that, its light ring glows red to alert you to dangerous smoke or CO levels, yellow for an early warning, blue to let you know that it’s ready to be connected, and white to light up dark hallways or rooms.

And on top of its CO sensor, it has a split-spectrum sensor, which detects smoke from fast- and slow-burning fires. Once it detects unhealthy levels of CO or smoke, this commercial carbon monoxide detector speaks in a friendly, human voice to warn you where the danger is.

Includes Google Nest Protect S3003LWES alarm-smoke carbon monoxide detector, 3 lithium AA batteries, mounting screws, backplate, 120V AC connector, three wire connectors, and user manual
Sensor type Split-spectrum sensor for smoke, electrochemical sensor for CO
Power source Corded electric and battery backup
Voltage 120 volts
Alarm noise level 85 decibels
Color White
Dimensions (L x W x H) 5.3 x 1.5 x 5.3 inches
Weight 16 ounces
Lifespan 10 years
Warranty 2-year limited warranty
5. First Alert Dual-Power Carbon Monoxide Detector CO615

With a digital backlit LED display and user-friendly features, the First Alert Dual-Power Carbon Monoxide Detector Alarm CO615 is one of the best carbon monoxide detectors that suits the needs of any homeowner. What users love most about this First Alert CO detector is that it accurately reads the current CO level and records the highest CO concentration since it was last reset.

While this commercial carbon monoxide detector works with any standard outlet, it also includes two AA batteries, offering a handy secondary power source during power outages. The unit even signals both audible and visual alerts once its batteries need to be replaced.

When this unit reaches the end of its life after 7 years or so, it generates signal chirps to let you know that you have to get a new one. And to warn you of dangerous CO levels, it sounds a loud 85-decibel horn, which you can turn off with a simple press of its test/silence button.

Includes First Alert CO615 dual-power carbon monoxide detector alarm, 2 AA batteries, and user manual
Sensor type Electrochemical
Power source Corded electric and battery backup
Voltage 120 volts
Alarm noise level 85 decibels
Material Non-precious metal
Color White
Dimensions (L x W x H) 3.4 x 1.7 x 5 inches
Weight 12 ounces
Lifespan 7 years
Warranty 7-year limited warranty
6. First Alert Carbon Monoxide Detector CO400

The cheapest of 2021’s best carbon monoxide detectors, the First Alert Carbon Monoxide Detector CO400 takes out the fuss of hardwiring and keeps you safe right away once it’s activated. While it’s affordable and easy to install, it still makes use of the most accurate CO sensor technology out there: electrochemical.

Since this First Alert carbon monoxide detector is completely battery-powered, you can put it wherever you prefer. It conveniently comes with a mounting bracket and a sensor that covers an entire room, so it takes the guesswork out of CO alarm installation.

Like the other First Alert detectors on the list, this one comes with a simple test/silence button, which lets you either stop the alarm or test if it’s working. Once it detects dangerous CO levels, it sounds a persistent 85-decibel horn, alerting everyone in the building to seek safety. And when its 9-volt battery runs out of power, this commercial carbon monoxide detector generates both an audible signal and a visual signal to warn you right away.

Includes First Alert CO400 carbon monoxide detector, 9-volt battery, mounting bracket, and user manual
Sensor type Electrochemical
Power source Battery-powered
Voltage 120 volts
Alarm noise level 85 decibels
Color White
Dimensions (L x W x H) 5 x 1 x 3 inches
Weight 7.2 ounces
Lifespan 5 years
Warranty 5-year limited warranty
7. X-Sense Smoke and Carbon Monoxide Alarm SC01

If you don’t want the hassle of frequently changing batteries or hardwiring an alarm, then the X-Sense Smoke and Carbon Monoxide Alarm SC01 is your best bet. Featuring a built-in lithium battery, it gives you 10 years of continuous battery power and 10 years of safety from smoke and CO—making it one of the best battery-powered carbon monoxide detectors on the market.

Because the X-Sense smoke and CO alarm is battery-powered, reviewers found it pretty simple to install. It comes complete with a mounting bracket and hardware; you can just mount it on the wall, and it’s ready to go. Another thing that users like about this unit is that it doesn’t require them to check and replace batteries every now and then.

Equipped with electrochemical and photoelectric sensors, this commercial carbon monoxide detector not only detects unhealthy CO concentrations but also dangerous smoke from both fast- and slow-burning fires. With a simple test/silence button, you won’t have a hard time testing the alarm weekly or silencing the alarm once a false alarm occurs.

This commercial carbon monoxide detector features a backlit LCD, which accurately indicates CO levels between 30 to 999 ppm. Once it detects dangerous smoke or CO levels, it sounds a loud 85-decibel alarm, waking up even the heaviest sleepers.

Includes X-Sense SC01 smoke and carbon monoxide alarm, mounting bracket, 3 screws, 3 anchor plugs, 2 carbon monoxide safety stickers, and user manual
Sensor type Photoelectric sensor for smoke, electrochemical sensor for CO
Power source Battery-powered
Voltage 3 volts
Alarm noise level 85 decibels
Material ABS plastic
Color White
Dimensions (L x W x H) 6.45 x 2.5 x 6.14 inches
Weight 1.01 pounds
Lifespan 10 years
Warranty 10-year limited warranty
8. Kidde Carbon Monoxide Detector KN-COP-IC

Another Kidde unit made the list of the best carbon monoxide detectors, and rightfully so. Like the first Kidde CO detectors, the Kidde Carbon Monoxide Detector KN-COP-IC has just the right features to guarantee safety against the silent killer.

Although this one doesn’t have a smoke detector like the Kidde KN-COSM-BA, it still features a unique voice alert, in addition to its standard alarm and LED light. Once it detects dangerous levels of CO, the voice alert feature shouts out “Warning! Carbon Monoxide!” at a loud 85-decibel noise level. The unit also comes with a digital display, which shows the current CO level, automatically updates the reading every 15 seconds, and displays the peak CO level since it was last reset.

In case of a power outage, you don’t have to worry about any lack of CO protection when you have this commercial carbon monoxide detector installed. It conveniently includes a 9-volt battery to keep it running even during a power failure and is built with a battery pull tab for easy battery replacements.

Want a fuss-free way of mounting your CO detector? This unit offers just that. It comes with a mounting bracket, which can be adjusted to let you easily install and perfectly align the detector. It even has a quick-connect feature and an included wiring harness, giving you an easy way of hardwiring it.

To deter any sort of tampering or prevent damage, this commercial carbon monoxide detector is designed with an anti-theft lock and a sealed cover. And to easily test and silence the alarm, it features a straightforward test/reset button.

Includes Kidde KN-COP-IC carbon monoxide detector, pack of mounting hardware, mounting bracket, wiring harness, and 9-volt battery
Sensor type Electrochemical
Power source Corded electric and battery backup
Voltage 120 volts
Alarm noise level 85 decibels
Color White
Dimensions (L x W x H) 5.75 x 5.75 x 1.8 inches
Weight 1.7 pounds
Lifespan 10 years
Warranty 10-year limited warranty
9. X-Sense Carbon Monoxide Detector CD07

Who doesn’t want the hassle-free installation of battery-powered CO alarms? We’ve included another carbon monoxide detector with a 10-year lifespan and 10-year battery: the X-Sense Carbon Monoxide Detector CD07. Its 10-year sealed lithium battery is enclosed in a fire-retardant and durable plastic frame, which makes it one of the best carbon monoxide detector options for commercial or residential use.

Fewer false alarms are what this commercial carbon monoxide detector offers. Instead of triggering the alarm right away, it confirms the CO level by taking three separate samples first. That way, it avoids disturbing you, as you’re sleeping, with a faulty reading.

To ensure that it’s working properly, this commercial carbon monoxide detector automatically inspects its battery and sensor every 10 seconds. Rather than generating a noisy alarm as you’re checking the alarm’s status, it features a LED indicator, which glows in three colors for different signals: red for alarm, green for active, and yellow for low battery. Reviewers love this feature because there’s no need to make deafeningly loud alarm tests.

With a large LCD, this X-sense carbon monoxide detector displays the CO level in ppm in real time and even updates its CO reading every 10 seconds. Plus, it records the peak level to show you the highest CO level measured since it was last reset.

Includes X-Sense CD07 carbon monoxide detector, mounting bracket, 3 anchor plugs, 3 screws, and user manual
Sensor type Electrochemical
Power source Battery-powered
Voltage 3 volts
Alarm noise level 85 decibels
Material ABS/PC plastic
Color White
Dimensions (DIA x H) 5.7 x 2 inches
Weight 14.8 ounces
Lifespan 10 years
Warranty 5-year warranty
10. First Alert Onelink Safe & Sound Smart Smoke and Carbon Monoxide Detector

If you’re interested in a smart CO alarm other than the Google Nest model, you might want to consider the First Alert Onelink Safe & Sound Smart Smoke and Carbon Monoxide Detector. Its smart features and hands-free control, among others, make it one of the best carbon monoxide detectors today.

What sets this commercial carbon monoxide detector apart from all others on the market is its built-in Alexa Voice Services, along with its high-end speakers and noise-cancelling microphones. Apart from giving you complete voice control over the unit, this feature lets you use it as a home intercom, call or text anyone hands-free, listen to music, audio books, and the news, and more. So not only will you be safe from dangerous CO levels with this device—you’ll also have an extra entertainment system.

On top of Alexa voice command and Amazon Echo features, this unit is compatible with Apple HomeKit, Apple Onelink Home Companion app, and AirPlay 2, so you can stream music and control it from your iPhone or iPad. It also comes with a nightlight feature, which comes with an autobrightness feature that glows in the dark and gets brighter in the day.

Besides these extra bells and whistles, this CO detector does not fall short of what you would expect from an effective CO safety device. It alerts you with an 85-decibel standard alarm, voice alarm, and mobile notifications once it detects dangerous levels of smoke or CO.

Includes First Alert Onelink Safe & Sound carbon monoxide detector, mounting bracket, mounting hardware, quick start guide, and user manual
Sensor type Photoelectric sensor for smoke, electrochemical sensor for CO
Power source Corded electric and battery backup
Voltage 120 volts
Alarm noise level 85 decibels
Color White
Dimensions (L x W x H) 6.8 x 6.8 x 2.26
Weight 1.5 lbs
Lifespan 10 years
Warranty 3-year limited warranty