The Best Carbon Monoxide (CO) Detectors of 2021

From smart carbon monoxide detectors to simple plug-in units, we found the best CO detectors available to keep your home and family safe. 

Best overall
nest protect product
Google Nest Protect
  • Icon Pros  Light
    Compatible with Nest Secure system
  • Icon Pros  Light
    Senses carbon monoxide, heat, and smoke
Best voice control
First Alert Carbon Monoxide Detector
First Alert OneLink
  • Icon Pros  Light
    Works with Amazon Alexa
  • Icon Pros  Light
    Voice alarm option
Easy Installation
kidde nighthawk plugin_product image
Kidde Nighthawk
  • Icon Pros  Light
  • Icon Pros  Light
    Plug-in with backup battery included

Nest Protect marries safety features like smoke, fire, and carbon monoxide detection with intuitive smart features. It's also a companion to your home security system and even a nightlight.

It comes with an option for voice alerts to minimize panic. And it connects to the Nest app, so you'll get alerts from anywhere.

Learn more in our full review of Nest Protect, or read on to compare this top carbon monoxide detector to our other favorites.

Compare CO detectors and alarms

After hours of research and testing, we’ve found the best carbon monoxide detectors and smoke detector combos available. From basic battery operated to smart carbon monoxide alarm devices, you can find the top options here.

Best overall Best voice control Easy installation Best value Budget pick

Nest Protect

First Alert OneLink

Kidde Nighthawk Plug in

Kidde Battery-Operated

Alert Plus Carbon Monoxide Detector

Nest protect
Alert Plus
List price






Smart features
Icon Yes  Light


Icon Yes  Light


Icon No  Light


Icon No  Light


Icon No  Light


Digital display
Icon Yes  Light


Icon No  Light


Icon Yes  Light


Icon No  Light


Icon No  Light


Smoke sensor
Icon Yes  Light


Icon Yes  Light


Icon No  Light


Icon No  Light


Icon No  Light


* prices as of 05/20/21 2:18 pm MST. See full disclaimer.

CO detector and alarm reviews

1. Google Nest Protect: Best carbon monoxide detector

Best Overall

Nest Protect combines smoke and carbon monoxide detection and works with an app. When you download it, you can get alerts to your phone and even silence alarms if necessary. With state-of-the-art sensors for both fire and carbon monoxide, this alarm is one of the best for homeowners or renters.

Pro Heading
Pro Bullet Works with other smart home devices
Pro Bullet Doubles as smoke detector
Pro Bullet Comes with battery or hardwire capabilities
Pro Bullet Features voice notifications
Con Heading
Con Bullet When the battery dies, you'll need a new alarm

You can't change the batteries in this carbon monoxide alarm, so you'll need to replace the whole thing once it expires. Even at $120, Nest Protect is still a good value if it lasts for its full life expectancy of 10 years.

Learn more about the Nest Protect in our full product review.

2. First Alert Onelink: Best voice control

Best Voice Control

The Onelink smart smoke and carbon monoxide detector can do a lot. Using your home’s Wi-Fi, the carbon monoxide alarms can talk to one another and synchronize to alert you if there is a gas leak or fire. You can also control it from your Apple device through an app, so you can silence the alarm or get notifications on your phone.

Pro Heading
Pro Bullet 10-year battery
Pro Bullet Mobile app
Pro Bullet Voice alarm
Pro Bullet Syncing system
Pro Bullet Built-in smoke alarm
Con Heading
Con Bullet Big price tag
Con Bullet When the battery dies, you'll need a new alarm

Onelink doesn't have a battery compartment that you can access, so when it dies you'll need to get a new CO detector. With a price tag over $200, that steep replacement cost might be more than some want to pay.

3. Kidde Nighthawk Plug-in: Easy installation

Best Value

When we say installing the Kidde Nighthawk carbon monoxide detector is easy, we mean it. You won't need drills, screws, or even batteries. Just plug it in, and it’s all set. It also comes with a 9-volt backup battery in case of a power outage.

Pro Heading
Pro Bullet Affordable price
Pro Bullet Digital display
Pro Bullet Positive customer reviews
Pro Bullet Backup battery
Con Heading
Con Bullet Not compatible with home automation
Con Bullet Hardwired only

Plug-in options like this CO detector keep renters and landlords happy. No need to drill holes in the wall.

Like other carbon monoxide detectors, it comes with a test button and LED screen to show the CO levels in your home. When the Nighthawk detects dangerous levels in your home, it will emit a signature beeping pattern so you won’t confuse it with any other alarms in your home.

Light Bulb
How do carbon monoxide detectors work for people with hearing loss?

Loud sirens are the standard for carbon monoxide detectors, but what if someone in your family has hearing loss? We found wire-in units that connect to smoke and carbon monoxide detectors that trigger a strobe light when there's an emergency.

4. Kidde Battery-Operated: Best value

Best value

The Kidde Battery Operated CO detector checks the air every 15 seconds for continuous monitoring with its electrochemical sensor. It doesn’t rely on hardwiring either, so it will continue to work even during a power outage. To top it off, it has a powerful 85 dB siren that sounds when it senses the poisonous gas.

Pro Heading
Pro Bullet No drilling required
Pro Bullet Test button
Pro Bullet Signature beep
Con Heading
Con Bullet No home automation
Con Bullet No smoke detection
Con Bullet No battery backup

While it lacks the smart features seen in the Nest and OneLink carbon monoxide detectors, it has all the marks of a reliable device. In addition to its loud siren and consistent monitoring, it has a green and red light to give visual safety cues to people with hearing loss.

If you need multiple CO detectors, this is a good device to start with. It’s affordable, dependable, and easy to install.

5. Alert Plus Carbon Monoxide Detector: Budget pick

Budget pick

The Alert Plus Carbon Monoxide and Smoke Detector is a simple device with one job—to keep you and your family safe from CO poisoning. And while it doesn’t have any smart features, it does have a powerful 85 dB siren to warn everyone in your home.

Pro Heading
Pro Bullet Affordable
Pro Bullet Batteries included
Con Heading
Con Bullet No smart features

It’s also one of the easiest devices to install. Just mount the backplate to the wall, add the batteries (included with the unit), and click the monitor into place.

And for under $20, you can afford to add more than one to your home. Place your Alert Plus CO detector in the basement, kitchen, garage, or anywhere you burn fossil fuels. We even saw reviews from users who kept it in their vehicle.

Types of carbon monoxide detectors

There are several types of carbon monoxide detectors available for purchase. Some include multiple functions:

  • Dual-function: sense different threats like CO, smoke, and fire
  • Digital: show you levels of carbon monoxide on a digital screen
  • Smart: run diagnostics and sync with home automation apps
  • Hardwired: wire into your home’s electrical grid, work unless the power goes out
  • Battery-operated: basic sensing and display, need batteries to operate

Our approach

To find the best carbon monoxide detectors, we compared smart features, installation ease, and detection accuracy. We also looked at user reviews to get a better idea of how these devices work first hand. Visit our methodology page to learn more about how we conduct reviews like this one.

Carbon monoxide detectors FAQ

Check out our full frequently asked questions page to learn more about carbon monoxide detectors. 

Carbon monoxide poisoning causes flu-like symptoms like dizziness, nausea, vomiting, headaches, confusion, or fainting. 

If you're at home, get out of the house and call 911. CO poisoning doesn't always hit suddenly and doesn't leave your system quickly, so it's a good idea to seek medical attention as soon as you can. 

Every year, 400 Americans die from accidental carbon monoxide poisoning and 20,000 are admitted to the emergency room.

Everyone is susceptible to carbon monoxide poisoning, but children, older adults, people who are physically ill, and pets are more likely to be affected by CO. 

Carbon monoxide detectors work like smoke detectors but detect levels of carbon monoxide instead. 

CO detectors usually have one or more of these sensors: 

  • Biomimetic detectors use color-changing gels that absorb carbon monoxide which triggers the alarm. 
  • Metal oxide semiconductors have silica chips that detect CO and send electrical signals to trigger an alarm. 
  • Electrochemical sensors use electrodes in chemical solutions that sense changes in electrical currents when carbon monoxide is present, and they sound the alarm. 


Most professionally monitored security systems come with a CO detector. Check out our top security providers to see which home security systems include CO detectors with their monitoring plans. 

Put a carbon monoxide detector outside every separate sleeping area in your home, your kitchen, basement, and garage. We recommend finding an area far enough away from the carbon monoxide source but close enough to the areas you and your family normally occupy. 

Check out our full guide on where to install your own carbon monoxide detectors. 

CO detector maintenance

Most carbon monoxide detectors last an average of five years. Although the product’s lifetime will vary depending on your make and model, you can still get the most out of your detector by wiping it down weekly to keep it clean from dust and debris.

Just like your smoke detectors, it's a good idea to test your CO detector monthly. Start by pressing the “test” button to ensure the siren works. If your detector is older, you can purchase a carbon monoxide meter to find out if your detector is still fully functional. If the carbon monoxide sensor doesn’t go off when you test it, it’s probably time to buy a new one.

Sources of carbon monoxide gas


Carbon monoxide (CO) has been called the “silent and invisible killer” because it doesn’t have a smell, color, or taste. It’s one of the most prevalent causes of death due to poisoning in America. Any time you burn something—like gasoline, natural gas, wood, oil, propane, or charcoal—carbon monoxide is released into the air.

In outdoor spaces, this usually isn’t a health hazard because there is enough area for the CO to dissipate, so particles never amount to a toxic level. The danger comes when carbon monoxide is released in a contained area like your home, RV, or garage.

Anything that burns will create carbon monoxide. It’s not just your stove, fireplace, or grill either. Here are some of the things that can create carbon monoxide when turned on:

  • Appliances
  • Gas grills
  • Gas stoves
  • Gas or oil-burning furnaces
  • Fuel-burning water heaters
  • Non-electric space heaters
  • Tools
  • Snowblowers
  • Lawnmowers
  • Pressure washers
  • Generators
  • Non-electric cars, trucks, and boats
  • Chain saws

Know what to do and what not to do

Lighting a fire in your fireplace is okay if it’s properly ventilated. However, if you do the following, you could cause dangerous levels of carbon monoxide to build in your home.


  • Always vent gas appliances properly
  • Get your chimney checked annually to ensure proper ventilation


  • Burn gas grills inside your home
  • Use your gas stove/oven for heating
  • Leave the car running with the garage door closed
  • Patch or seal vent pipes with tape or unapproved products or carbon monoxide could leak into your home
  • Burn charcoal inside
  • Run a generator in your home or within 20 feet of your home’s doors, windows, and garage
  • Turn on your car if the tailpipe is blocked (by snow or anything else)

Related pages


* list price as of 05/20/21 2:18 pm MST. Product prices and availability are accurate as of this date/time indicated and are subject to change. Any prices and availability information displayed on Amazon at the time of purchase will apply to the purchase of this product. utilizes paid Amazon links.

Certain content that appears on this site comes from Amazon. This content is provided “as is” and is subject to change or removal at any time.

Katie McEntire
Written by
Katie McEntire
As a renter, pet-owner, and woman living alone, Katie McEntire takes safety seriously. She’s tested devices like pet cameras, home security systems, and GPS trackers in her own home and devices in the name of safety. In addition to testing, writing, and reviewing for SafeWise, she also makes videos for the site’s YouTube channel. She’s been featured on publications like TechGuySmartBuy, Forbes, Healthy Moms, and Digital Care. Katie has a Bachelor’s degree in Technical Writing from Austin Peay State University in Clarksville, Tennessee. She’s held previous writing positions at and Top Ten Reviews.