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Published Jun 29, 2022 1:00 PM

A carbon monoxide detector, or CO alarm, is an essential safety device for renters and homeowners. Without one, you risk exposing yourself and your loved ones to accidental CO poisoning, which kills more than 400 Americans yearly, according to the Centers for Disease Control (CDC). There’s a chance you already have a carbon monoxide detector at home, as they’re sometimes (but not always) built into smoke detectors. If you don’t have one, they’re affordable and very easy to install. Whether you’re replacing a faulty CO alarm or upgrading an older home to meet local health codes, these are the best carbon monoxide detectors.

What is carbon monoxide?

Carbon monoxide is an odorless, tasteless, poisonous gas that builds up when you burn fuel like gas, wood, or coal. If inhaled, carbon monoxide blocks your ability to absorb oxygen into your blood, and by extension vital organs including your heart and brain. In a gas-filled room, inhaling carbon monoxide can render you unconscious and kill you within a few minutes, according to reports from the CDC and OSHA. And though symptoms of CO poisoning include headaches, dizziness, chest pain, and vomiting, victims are unaware that they’re being poisoned until it’s too late. 

Using a battery-operated carbon monoxide detector is considered one of the most effective ways to protect yourself from CO poisoning. For ways to prevent carbon monoxide poisoning, particularly in winter when it’s most common, we have some tips on how to protect yourself.

How does a carbon monoxide detector work?

Carbon monoxide detectors aren’t as complicated as they seem. While some models feature different components, they generally feature a silicon microchip that sends an electronic charge to other parts of the detector. If a dangerous level of CO is detected, an audible alarm, usually 85 decibels, will sound.

Carbon monoxide is measured in parts-per-million (PPM). According to this chart, it may take between 6 – 8 hours for physical symptoms to manifest when exposed to 50 PPM of CO. Triple that to 150 PPM of CO and you may experience symptoms in as little as 2 – 3 hours. And 800 PPM of CO can be fatal within an hour. If your CO alarm goes off, immediately go outside and only reenter when emergency responders say it’s safe.

How we chose the best carbon monoxide detectors

I’ve been covering technology since 2011 for publications like Popular Science, CNN Underscored, and TechnoBuffalo. To make our recommendations, I considered research into carbon monoxide and safety protocols for preventing CO poisoning, from reports and government-issued guides from sources like CDC.gov, MayoClinic.org, and HopkinsMedicine.org. We also checked out the testing of carbon monoxide detectors from professional reviewers.

Things to look for when choosing the best carbon monoxide detectors

A good carbon monoxide detector should be easy to install, require little maintenance, and effectively alert you when there’s an emergency. We considered dozens of options and whittled down the field until we found the best carbon monoxide detectors available. Here are the most important things to check before purchasing one.

UL listing

A good carbon monoxide detector should have received certification from Underwriters Laboratories, a safety science organization that sets technical standards for CO alarms and other safety gear. The company’s most recent standards, UL 2034, require CO alarms used in living spaces to detect and report carbon monoxide levels below those that cause a loss of ability to react to dangerous exposure. Any device that meets UL’s standards should mention that it’s “UL Listed” somewhere on the packaging.

Power on

Carbon monoxide detectors come in a few form factors, based on how they receive power:

Battery-powered: A battery-powered (typically 9-volt or AA) CO alarm is the most flexible because you can easily install it in virtually any room in your home. This is an excellent option for places with no electricity, like a detached garage or shed where you might be working on an old car.

Plug-in: Outlet-based detectors don’t need battery replacements, but you’ll need to place them where you have an outlet, and will not work when your power goes out. A good model will also feature a battery backup, in case your home loses power.

Hardwired: You can also have a permanent CO detector installed in your home. Like plug-in models, a good model will include a backup battery for when your power goes out. We recommend hiring an electrician or contractor to handle any installation that requires interfacing with your home’s power.

Homeowners, particularly those planning a renovation, should probably consider installing a hardwired model. Renters and people with older homes may want to use a plug-in or battery-powered option. If there are detectors in the space you currently live in and you’re unsure about when they were replaced, you should probably buy new ones. You can see if yours are hardwired or battery-powered by removing them from their mounts.

Lastly, if you pick a plug-in or hardwired model, make sure that it features an easily replaceable backup battery. The CDC recommends replacing the battery in your CO alarm every six months.

Smart features

A smart carbon monoxide detector connected to your home WiFi can send an alert to your phone when you aren’t home. New CO detectors also tend to have much more intuitive controls for basic functions like muting the alarm and battery tests. Some also offer voice alerts when an issue arises, and can even tell you which room is the source of the gas buildup.

The best carbon monoxide detectors: Reviews & Recommendations

We have enough things to worry about in our everyday lives, without the creeping fear of colorless, odorless gas leaks in the back of your mind. If you don’t use a carbon monoxide detector, it’s time to start. If you’re buying your first CO alarm or need to replace an older model, our recommendations offer reliable CO detection and a few extra features.

Best overall: Kidde Nighthawk Carbon Monoxide Detector

Buy used or refurbished: eBay

Why it made the cut: The Kidde Nighthawk features a digital display, battery backup, and corded adapter for extra mounting flexibility.

Specs

  • Type: Plug-in
  • Battery backup: Yes (9 volt)
  • Dimensions: 6.1 x 3.8 x 1.8 HWD

Pros

  • Digital display
  • Battery backup
  • Corded adapter offers more mounting flexibility

Cons

  • No interconnection or smart features

The Kidde Nighthawk is more than just a cool name. This plug-in dual carbon monoxide and explosive gas detector comes equipped with a digital display that tells you the current CO concentration, which updates every 15 seconds to indicate any sudden changes. If unhealthy CO levels are detected, the Nighthawk will emit four quick audible beeps every five seconds until levels decrease or the reset button is pressed.

For a plug-in model, the Nighthawk is very flexible. You can plug it directly into the wall, or use its 6-foot AC power adapter to mount it higher on your wall. Crucially, the Nighthawk also supports a 9V battery backup, so it will continue running if your power goes out. The Nighthawk is easy to install and use. It has some extras, but nothing over-complicated that might make it excessively expensive or complicated. That’s exactly what you want from a device that you only want to interface with in an emergency.

Best smoke and carbon monoxide detector: Kidde Smoke & Carbon Monoxide Detector

Buy used or refurbished: eBay

Why it made the cut: The smoke and carbon monoxide detector from Kidde consolidates two essential safety devices into one, giving you double the protection.

Specs

  • Type: Battery-powered
  • Battery backup: Yes (AA x 2)
  • Dimensions: 5.6-inch diameter x 1.8-inch depth

Pros

  • Easy to install
  • Provides smoke alerts
  • Voice alarm

Cons

  • No digital display

Kidde’s combination smoke and carbon monoxide detector is a simple upgrade for your old smoke detector. It’s battery-powered, features voice alerts, and offers a 10-year lifetime warranty for long-term protection. It’s simply designed, with a prominent button in the middle for testing and hushing the alarm. If a dangerous level of CO is detected, the Kidde will sound with four beeps and say, “warning carbon monoxide.” It also provides a vocal “fire” warning and lets you know when its battery is low. Though it is not a “smart” device, per se, you can sync up to 24 Kidde safety devices, including up to 12 smoke alarms, for a more thorough, multi-alarm system.

Best plug-in detector: First Alert CO615

FIRST ALERT

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Buy used or refurbished: eBay

Why it made the cut: The First Alert CO615 features a digital display, so you’ll always know the CO levels in your space.

Specs

  • Type: Plug-in
  • Battery backup: Yes (AA x 2)
  • Dimensions: 5 x 3.4 x 1.7 inches HWD

Pros

  • Digital display
  • Battery backup
  • Corded plug-in

Cons

  • Trickier mounting hardware

Similar to our top pick, the First Alert CO615 is a plug-in CO alarm with a digital display and backup battery in case there’s a power failure. The digital display makes it easy to check CO levels at a glance at any time. The peak level button shows the highest level of carbon monoxide measured, which can help you tell if your current levels are abnormally high. It also features an 85-decibel alarm, a hush button, and an end-of-life signal chirp, so you’ll know when it’s time to replace the unit. These features are easy to use and understand, making the First Alert CO615 an excellent plug-in option.

Best smart: Google Nest Protect Smoke and Carbon Monoxide

Google

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Buy used or refurbished: eBay

Why it made the cut: The Nest Protect from Google provides double the protection and a powerful mobile app that lets you hush alarms and receive notifications when you’re away.

Specs

  • Type: Battery-powered or wired
  • Battery backup: Yes; battery-powered (AA x 6), Yes; wired (AA x 3)
  • Dimensions: 5.3 x 5.3 x 1.5 inches HWD

Pros

  • Mobile alerts
  • Easy to silence from your phone
  • Powerful interconnectivity features

Cons

  • Expensive

The Google Nest Protect features smoke and carbon monoxide detection and can send mobile alerts to users when they’re away. The Protect also makes it easy to silence an alarm through the Nest app (or by pressing the mute button) and provides voice alerts when there’s an issue. 

Of course, Nest Protect’s real selling point is an array of smart features, including the ability to control basic functionality through the Nest app and detect the source of CO buildup. The Nest Protect is a great way to integrate smoke and CO protection into your smart home setup if you’re already using other Google Nest appliances, such as a smart thermostat or smart doorbell. It’s more expensive than the other options, but it also offers much more control.

Best budget: Kidde Carbon Monoxide Detector

Buy used or refurbished: eBay

Why it made the cut: Kidde’s Carbon Monoxide Detector is easy to use, easy to understand, and offers battery backup in case of a power outage.

Specs

  • Type: Plug-in
  • Battery backup: Yes (AA x 2)
  • Dimensions: 4.5 x 2.75 x 1.5 inches HWD

Pros

  • Battery backup
  • Straightforward operation
  • Will alert you if it comes unplugged

Cons

  • No digital display
  • No corded plug

A solid carbon monoxide detector doesn’t need to be complicated or expensive. The Kidde Carbon makes it very easy to tell if the CO level in your home is too high. If the light is green, you’re good. If it’s red, get outside. The CO alarm also features a battery backup, an end-of-unit alarm, and a convenient test/reset button on the front. It doesn’t provide as much information as our other picks, but the Kidde Carbon gets the job done and costs less.

FAQs

Q: How often should you replace a carbon monoxide detector?

The National Fire Protection Association (NFPA) recommends testing your CO alarm at least once a month and replacing them according to the manufacturer’s instructions. CO detectors typically last seven to 10 years, depending on the model. Replacing your CO alarm in that timeframe will also ensure your detectors meet updated standards.

Q: Where is the best place to put a carbon monoxide detector?

We recommend following the manufacturer’s instructions to determine where to place your specific carbon monoxide detector. That said, the Environmental Protection Agency (EPA) recommends placing a carbon monoxide detector about five feet above the floor or ceiling. Carbon monoxide is slightly lighter than air and mixes with warm, rising air, which is why you want a CO alarm off the ground. You should also avoid placing it somewhere you may expect higher CO levels, like next to a fireplace.

Q: How many carbon monoxide detectors should you have in your house?

The United States Consumer Product Safety Commission (CPSC) recommends installing a CO alarm on each level of your home (including your basement), outside sleeping areas, and inside each bedroom. Experts recommend you place several CO alarms throughout your home, as there may be areas where they do not work as intended, such as in the bathroom, next to heating appliances, or near a fireplace.

Q: Is a battery-powered, plug-in, or hardwired carbon monoxide detector better?

Each type has pros and cons, so it will ultimately come down to what works best for your space. Hardwired models require professional installation, but don’t require an outlet for power. Plug-in models are arguably the most convenient to move or replace, but take up an outlet and often wind up in outlets near the floor, which makes for poor placement. 

Battery-powered CO detectors can be installed anywhere and won’t fail when the power goes out. One could argue they require more maintenance, as you’ll need to replace their batteries. Then again, you’ll need to do the same thing with the backup batteries for plug-in and hardwired CO detectors, so it isn’t really much more of a burden.

Final thoughts on the best carbon monoxide detectors

A carbon monoxide detector should be in every apartment and home worldwide. They not only protect you from CO poisoning, but they’re affordable and easy to install, giving you no excuse not to take action. If you don’t have one, you should purchase one as soon as possible because it can mean the difference between life and death.

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