Best Carbon Monoxide (CO) Detectors

You need a carbon monoxide detector to protect against accidental poisoning. Here are our suggestions.

Whether you want the cheapest option or the finest technological advancements, we’ve got a CO detector recommendation.

Why? In the US, at least 450 people die of carbon monoxide (CO) poisoning each year. Another 50,000 wind up in the emergency room because they’ve inhaled the odorless but deadly gas.¹ You can keep yourself from being one of these numbers by installing a carbon monoxide detector.

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How we chose
We looked at nearly 40 different carbon monoxide detectors and winnowed it down to five top choices.
Best carbon monoxide detectors
NamePricePower sourceSmoke alarmSee details
Kidde KN-COPP-3$71.50Plug

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Kidde KN-COSM-BA$24.99Battery

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Nest Protect$115.00Battery or wired

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Onelink Safe & Sound*$249.99Plug

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Kidde KN-COB-LP2 9CO5-LP2$14.20Battery

View on Amazon List Prices (as of 06/17/2021 3:20 MST). Offers subject to change.

*Currently not sold by the manufacturer on Amazon

Kidde Nighthawk KN-COPP-3 Carbon Monoxide Alarm Detector: Best traditional option

The Kidde KN-COPP-3 is the best conventional carbon monoxide sensor. It’s plain, but it does what needs to be done.


  • Excellent reputation
  • Digital display
  • Six-foot cord
  • 9-volt battery backup
  • Five-year limited warranty


  • Plug-in only
  • No smoke alarm
  • No home automation

Why we chose Kidde KN-COPP-3

We picked this Kidde detector largely because of its reputation. This device may be old school, but it’s one of the (if not the) best-reviewed carbon monoxide alarms we considered.

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What’s Nighthawk?
We aren’t talking about the Marvel superhero. Nighthawk is a name Kidde uses for its sensor technology.

Both customers and experts alike gave this alarm high ratings, and for good reason. It has a digital display and a generous five-year warranty. And, yeah, it’s plug only, but the six-foot cord means it doesn’t have to be right by an outlet.

The downside

Even with a long cord, a plug-in alarm can be a hassle in some cases. And if you’re looking for a carbon monoxide-smoke detector combo, this isn’t right for you.

Also, if you’re big on home automation, know that this device won’t sync with a voice assistant or other equipment.

Kidde KN-COSM-BA Combination Smoke/Carbon Monoxide Alarm: Best combo

Looking for a reliable combo alarm that’s not crazy expensive? We’ve found one.


  • Smoke detector
  • Voice warnings
  • Moderate price
  • Battery-powered
  • Five-year limited warranty


  • No digital display
  • Not for home automation

Why we chose Kidde KN-COSM-BA

For those who want the two-in-one safety of a smoke alarm-carbon monoxide detector combo, the KN-COSM-BA is a solid choice. This detector isn’t too expensive, and it runs on batteries rather than needing a plug or wires.

Our favorite feature, though, is the voice warnings. When the alarm goes off, it vocally announces either “Fire,” or “Warning: carbon monoxide,” so you know what you’re dealing with.

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Do I need a smoke alarm in my carbon monoxide detector?
Not necessarily. Carbon monoxide gas doesn’t rise or fall, so it can usually be found in equal concentrations throughout a home.² So while you should put your smoke detector on the ceiling, you might want to disperse carbon monoxide alarms at different levels throughout your home. In that case, it might make sense for some or all of your devices to detect carbon monoxide only.
The KN-COSMA-BA comes with a limited five-year warranty.

What if it breaks? Like the KN-COPP-3 carbon monoxide detector, this Kidde device comes with a five-year limited warranty.

The downside

The Kidde KN-COSMA-BA doesn’t have a digital display. That means there’s no screen to show the carbon monoxide levels or other metrics. And, like the KN-COPP-3, it wasn’t made for smart home use. You can’t hook it up to your other devices.

Nest Protect Smoke and Carbon Monoxide Detector: Best for Google Assistant

For all you Google Assistant users out there, this one’s for you.


  • Smoke detector
  • Voice warnings
  • Google Assistant compatibility
  • Google Nest Secure compatibility
  • Can be battery-operated or hardwired
  • Two-year limited manufacturer warranty


  • Confusing physical interface
  • No digital display

Why we chose Nest Protect

If you swear by your Google Home, or if you’ve already invested in a Google Nest Secure security system, the Nest Protect is a safe bet. It’ll integrate smoothly with your existing setup. It’s also flexible; you can have it hardwired or just use batteries.

This high-tech smart device features a smoke detector and voice warnings, similar to the Kidde KN-COSMA-BA. You’ll get mobile notifications for alarm events and when the batteries need to be changed. And if you need to turn the alarm off, you’ll tap the Nest app to silence the system from anywhere.

Your device has a two-year limited manufacturer warranty to protect your Nest Protect.

The downside

It’s convenient to use remote access to silence your carbon monoxide detector/smoke alarm. But we wish there was also a more obvious button on the Nest Protect for times when your phone isn’t handy.

It took us some digging to realize that the circle in the middle, which lights up when the alarm goes off, is also the silence button. If you forget that little detail, you’ll be forced to listen to the incessant beeping of the alarm while you search for a way to turn it off.

Similarly, the device doesn’t have a digital display to show you the carbon monoxide levels. You’ll have to go to the app.

Onelink Safe & Sound by First Alert: Best for Alexa

Onelink is our pick for Amazon Alexa users.


  • Smoke detector
  • Voice warnings
  • Compatible with Alexa
  • Built-in Alexa speaker
  • Battery backup
  • Three-year warranty


  • Expensive
  • Plug-in only
  • No digital display

Why we chose Onelink Safe & Sound

Onelink is the best option if you want something to work with your Alexa-enabled smart home. The Onelink Safe & Sound is quite similar to the Nest Protect, right down to the smoke detector combo and voice warnings.

But the Onelink offers a little more than the Nest Protect. It has an Alexa speaker built right into it. The speaker doesn’t just control the carbon monoxide detector either; you can use it for other Alexa voice commands.

Lastly, with a Onelink Safe & Sound, you get a three-year warranty. It’s not as extensive as the Kidde detectors’ warranties, but it’s better than Nest Protect’s.

The downside

This bad boy’s extremely expensive. For the price of a Onelink, you could buy two and a half Nest Protects and still have enough money to get lunch from the McDonald’s dollar menu.

The Onelink also shares Nest Protect’s lack of a digital display. We think it’s cool to control your detector from a mobile app, but again, it’s also nice to look at the device and immediately know its status.

Also, you have to plug this detector in. The backup battery is for power outages, not for day-to-day use.

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First Alert
First Alert, the company that produces the Onelink Safe & Sound, says that it sold the first residential smoke alarm in 1958.

Kidde KN-COB-LP2 9CO5-LP2 Carbon Monoxide Detector Alarm: Budget pick

The Kidde KN-COB-LP2 9CO5-LP2 is very cheap but minimalistic.


  • Affordable
  • Battery-powered
  • Five-year limited warranty


  • No smoke alarm
  • No digital display
  • Not for home automation

Why we chose Kidde KN-COB-LP2 9CO5-LP2

If finances are tight, this is the pick for you. The Kidde KN-COB-LP2 9CO5-LP2 is very inexpensive; at the time we’re writing this, it’s less than $20 on Amazon. But it also comes from Kidde, one of the top carbon monoxide detector manufacturers, so it should be quality even with the price cut.

This battery-powered alarm has a five-year limited warranty.

The downside

To get that low, low cost, Kidde stripped away any extras. This alarm doesn’t have a smoke detector or a digital display. And it’s not a smart product; you can’t mesh it with your connected home network.


Still deciding? Let’s run through each of our recommendations one last time.

Kidde KN-COPP-3: Best traditional option—If you seek a basic, traditional option, then this is what we recommend.

Kidde KN-COSM-BA: Best combo—Try this Kidde alarm to harness the power of both carbon monoxide and smoke detection.

Nest Protect: Best for Google Assistant—We recommend Nest’s homegrown product for Google Assistant enthusiasts.

Onelink Safe & Sound: Best for Alexa—Likewise, the Onelink is perfect for Alexa lovers.

Kidde KN-COB-LP2 9CO5-LP2: Budget pick—If you don’t want to spend much money, try this super cheap Kidde option.

If you’re looking for a straight-up smoke alarm, check out this guide. Or, if you want more robust protection, consider a full security suite.

Carbon monoxide detector FAQ

What are the symptoms of carbon monoxide poisoning?

According to the CDC, symptoms of CO poisoning are as follows:

  • Headache
  • Dizziness
  • Weakness
  • Upset stomach
  • Vomiting
  • Chest pain
  • Confusion³

These might seem like pretty distinct symptoms at first blush, but things aren’t always so straightforward in the moment.

There’s a famous Reddit tale about a man who believed his landlord was leaving him mysterious notes around his apartment. Turned out, he was actually confused due to high carbon monoxide levels in his rental—he’d written the notes himself.

Having a carbon monoxide detector means that your bewildered brain doesn’t have to play detective. You’ll know that you’re being poisoned and can get out.

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Carbon monoxide gas is measured in PPM (parts per million). 101 PPM and over are considered dangerous levels.⁴

What should I do if my home has dangerous levels of CO?

Get out. You need to get some fresh air to recover. If someone is experiencing major symptoms, call 911. If not, call your local fire department.⁵

Can I get a carbon monoxide detector through my home security company?

In many cases, you can. ADT and SimpliSafe both sell carbon monoxide alarms that integrate with their systems, and they aren’t the only ones.

Ring Alarm also has an Alexa-compatible offering called a smoke and CO “listener.” Install this little beauty near your previously existing alarms. When one goes off, the listener lets you know through a mobile notification.

Where should I put my carbon monoxide detector?

Put a sensor in areas susceptible to CO buildup, like in your garage or RV or near fuel-burning furnaces, stoves, water heaters, fireplaces, and generators.

It’s also smart to put detectors in bedrooms and highly trafficked living areas. You want the detectors to be where you are so that you’ll be notified of high levels immediately.

Can I get a portable carbon monoxide detector?

Yes. For instance, you could try this Forensics Car and Aircraft Carbon Monoxide Sensor. It’s meant for vehicles, but you might be able to use it elsewhere.

There’s also the waterproof, shockproof Sensorcon. You can carry this CO alarm throughout different rooms in your house if needed—though we recommend it primarily for hotels.

What’s a limited warranty?

A limited warranty can be tricky. It’s left to the retailer’s discretion to decide what the warranty covers. So your warranty might cover accidental damage but not normal wear and tear. Or it might include the hardware but not the repair labor.⁶ Or it might be utterly void if you purchased the product through a third party, even on a reputable site like Amazon.

Be smart about your carbon monoxide detector’s warranty. Read the conditions and terms thoroughly and follow them so you aren’t on the hook for repair and replacement costs.


  1. Centers for Disease Control and Prevention, “Carbon Monoxide (CO) Poisoning Prevention
  2. Intermountain Healthcare, “Protect Your Family: Install Carbon Monoxide Alarms
  3. Centers for Disease Control and Prevention, “Frequently Asked Questions
  4. Kidde, “What Are the Carbon Monoxide Levels That Will Sound the Alarm?
  5. Kidde, “Carbon Monoxide Poisoning FAQs
  6. FindLaw, “What Is the Difference Between a Full Warranty and a Limited Warranty?

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