The 8 Best Carbon Monoxide Alarms of 2021

Prioritize your safety by installing these alarms

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Best Carbon Monoxide Alarms

The Spruce / Chloe Jeong

Carbon monoxide is a serious safety concern for homeowners, especially those with gas appliances or hookups in their house. Because carbon monoxide is a colorless, odorless gas that can be deadly, testing for carbon monoxide is a must-do. The most important thing to look for in a quality detector is its ability to actually detect carbon monoxide in the environment. You can also look for a unit that can detect additional threats, such as smoke or fire. You should opt for a unit that is easy to install (or pay a professional to do installation of a more complex system). Some units can be connected to other home safety devices or alarms in other rooms to ensure that you are always notified when there are unsafe levels of carbon monoxide in your home.

Here are the best carbon monoxide alarms to ensure that your home stays safe and you stay alert.

Our Top Picks
This plug-in model has a battery back up and a digital display so you can easily see the carbon monoxide level at any moment.
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Affordable and easy to install, this carbon monoxide detector comes with two AA batteries, and an 85 decibel alarm.
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Able to connect with other Google Home devices, this smart device monitors both smoke and carbon monoxide and can send alarms to a phone.
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It can detect carbon monoxide anywhere in the room, is easy to install, and has a battery back up.
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This carbon monoxide detector comes with a lithium battery that is already installed and lasts for 10 years.
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Hardwired, this combination smoke and carbon monoxide detector sends voice alerts and provides the location of the problem.
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This three-pack of hardwired units detect both smoke and carbon monoxide, have battery back ups, and can be linked together.
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This unit comes with both a voice and a visual LED alert so you can be notified of what the problem is when it happens.
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Best Overall: Kidde Nighthawk Plug-In AC/DC Carbon Monoxide Alarm Detector

Kidde KN-COPP-3 Nighthawk Plug-In Carbon Monoxide Alarm with Battery Backup

Power Source: Plug-in (battery backup) | Voltage: 9 volts | Digital Display: Yes | Smoke Detector: No

What We Like
  • Digital display

  • Plug-in and battery power

What We Don't Like
  • No smoke detector

  • No voice alarm

Because safety is such a major concern, I always lean toward a product that has two sources of power to ensure that I always know that my home is safe. The Kidde Nighthawk Carbon Monoxide Detector is a plug-in unit with a battery backup. Even if you lose power, the batteries will ensure that the alarm still functions. If you aren’t on top of changing the batteries, the continuous plug-in power is there. You can use this alarm plugged into a wall outlet (most of which happen to be at ideal levels to detect carbon monoxide), wall-mounted, or on a table.

I also like the digital display that tells you exactly what the level of carbon monoxide is at any given moment. This helps interpret the many possible alarms that carbon monoxide detectors can give, such as low battery or end-of-unit-life. I have purchased and used this carbon monoxide detector in two homes over the years.

What Testers Say

"After ten years, the Nighthawk’s end of life alarm will sound repeatedly to let you know it’s time to replace the whole unit. That really gave us some peace of mind."—Stacey L. Nash, Product Tester

Best Budget: Kidde Battery-Powered Carbon Monoxide Detector

 Kidde Battery-Powered Carbon Monoxide Detector

Power Source: Battery | Voltage: AA batteries (1.5 volts) | Digital Display: No | Smoke Detector: No

What We Like
  • Audible alarm

  • Easy to install

  • Budget-friendly

What We Don't Like
  • No digital display

If you’re looking for a reliable carbon monoxide detector that will keep your home safe without any extra bells and whistles, the Kidde Carbon Monoxide Detector has just what you need. It is battery-operated and easy to mount on the wall or use on a tabletop. When it detects unsafe levels of carbon monoxide, it sounds an 85 decibel alarm which will wake up your family at night or alert you during the day. At less than $15, it is an affordable investment in your family’s safety that will work with any budget. It even includes two AA batteries, adding to the cost savings.

Best Splurge/High-End: Google Nest Protect Wired Smoke and Carbon Monoxide Detector


Power Source: Battery or hard-wired | Voltage: 1.5 volts | Digital Display: No | Smoke Detector: Yes

What We Like
  • Integrates with Google smart home products

  • Detects smoke and carbon monoxide

  • Modern-looking

  • Expensive

For the most aesthetically-pleasing and high tech option, the Nest Protect from Google has all of your home safety needs covered in a futuristic-looking console that can be mounted on the wall and accessed via your smartphone. You can monitor the smoke and carbon monoxide levels remotely, receive alarms on your phone as well as via a voice alarm from the unit, and even check on the battery life. This is a pretty expensive detector and alarm, though, so just be ready to pay a hefty price for its advanced features and integration with your Google home devices.

Best Plug-In: FIRST ALERT CO605 Plug-In Carbon Monoxide Detector

First Alert CO605 Plug-In Carbon Monoxide Detector

Power Source: Plug-in | Voltage: 120 volts | Digital Display: No | Smoke Detector: No

What We Like
  • Detects carbon monoxide from anywhere in room

  • Easy installation

  • Budget-conscious

What We Don't Like
  • No digital display

The sensor in this carbon monoxide alarm from First Alert can work no matter where the alarm is located in your room. This provides additional flexibility for those who want to plug in the detector in an out-of-the-way outlet or who don’t have as many options available based on the electrical outlet setup in their home. It does come with a battery back-up, which I always recommend when considering a plug-in model. While it doesn’t have a fancy display, it will still provide the alarm that you need to ensure your home’s safety against deadly carbon monoxide poisoning without breaking the bank.

Best Battery: Kidde 10 Year Worry-Free Sealed-In Lithium Battery Carbon Monoxide Detector

Kidde 10 year worry-free carbon monoxide alarm

Power Source:  Battery | Voltage: 3 volts | Digital Display: No | Smoke Detector: No

What We Like
  • Installed lithium battery

  • No need to change battery

  • Easy installation

What We Don't Like
  • No smoke detection

  • No digital display

Even though this carbon monoxide detector is battery-powered, the installed lithium battery is good for the 10 year lifespan of the alarm. This means that you can enjoy the convenience of a battery-powered unit without ever worrying about changing the battery. It only detects carbon monoxide and doesn’t have a digital interface, but the convenience of set it and forget it can’t be beat.

Best Hardwired: First Alert AC Hardwired Combination Smoke and Carbon Monoxide Detector

AC Hardwired Combination Smoke and Carbon Monoxide Detector with Voice Alert

Power Source:  Hardwired (with battery backup) | Voltage: 120 volts | Digital Display: No | Smoke Detector: Yes

What We Like
  • Smoke and carbon monoxide detection

  • Installation adaptors

  • Voice and location alerts

What We Don't Like
  • No digital display

This handy unit detects slow, smoldering fires, high levels of carbon monoxide, and heavy smoke. It is hardwired but also has a battery backup to make sure that even if you lose power, the unit itself still works. One of the best features of this First Alert system is that it alerts you using a voice alert and provides the location of the source. Hardwired systems can be a bit more challenging to install, but the First Alert combo alarm comes with adaptors to make it compatible with any other hardwired mounts that you already have.

Best Multi-Pack: First Alert BRK 9120B-3 Hardwired Smoke and Carbon Monoxide Detector with Battery Backup, 3 Pack

 FIRST ALERT BRK SC9120B-3 Hardwired Smoke and Carbon Monoxide (CO) Detector

Power Source: Hardwired (with battery backup) | Voltage: 1.5 volts | Digital Display: No | Smoke Detector: Yes

What We Like
  • Savings over single purchase

  • Integrate together

  • Hardwire with battery backup

  • Smoke and carbon monoxide detector

What We Don't Like
  • No digital display

It is a good idea to put a carbon monoxide detector on each level of your home or near each bedroom. This is especially important for those with gas appliances or utilities that could be a source of a carbon monoxide leak. This is why buying a multi-pack of carbon monoxide detectors is so common and can save money. The 3-pack from First Alert is available in a hardwired version with a battery backup to ensure that you are always protected. You can also purchase this reliable detector in a 6-pack if you have multiple homes to outfit. These alarms can be linked together so that they will all sound, no matter where the unsafe levels of carbon monoxide are detected.

Best with Smoke Detector: Kidde Battery-Operated Combination Smoke/Carbon Monoxide Alarm with Voice Warning

Kidde Smoke & Carbon Monoxide Detector

Power Source: Battery | Voltage: 1AA battery (1.5 Volts) | Digital Display: No | Smoke Detector: Yes

What We Like
  • Combo smoke and carbon monoxide detection

  • Voice alert

  • Visual alert

What We Don't Like
  • Not hardwired

If you want one unit that can alert you to dangers from both fire/smoke and carbon monoxide, the Kidde Smoke and Carbon Monoxide Detector with Voice Alarm is easy to install, effective at monitoring both smoke and carbon monoxide, and easy to understand. The voice alert feature tells you which danger you need to take action to deal with in a calm, easy-to-understand voice. It also has a visual LED alert to provide another means of notification. It operates on a battery, but you can still connect it to other Kidde products as part of a larger system if you want.

What Testers Say

"To install the batteries (two AA), we just had to open the compartment door and slide them in. We like that changing the batteries doesn’t require removing the detector from the base."—Katie Begley, Product Tester

Final Verdict

Our top pick is the Kidde Nighthawk Carbon Monoxide Detector (available at Amazon) for its great features, budget-friendly price, and easy installation. The two power sources (plug-in and battery) and the digital display make it the top choice for me. If you have the room in your budget, the smartphone compatibility of the Google Nest Protect Smoke Alarm, Detector, and Carbon Monoxide Detector (available at Amazon) makes it easy to monitor and respond to any safety hazards in your home no matter where you are.

What to Look for in a Carbon Monoxide Alarm

Smoke Detection

Some carbon monoxide detectors can do more than just monitor for unsafe CO levels. They can also alert you to smoke or slow, smoldering fires in your home. These combination units can be more expensive than a carbon monoxide-only detector, but still cheaper and easier to install than two separate CO and smoke detectors individually.


Hardwired units are the most complicated to install, especially if you do not already have a base station with electrical wires run. Some have adaptors that allow you to mount their unit on another company’s base without any major changes to your home. A plug-in carbon monoxide detector is easier to install, as long as you have an accessible power outlet. A battery-powered unit is the easiest to install, since all you need is a place to hang the detector on the wall or set it on a flat surface.


If you have a large home, you may want to prioritize having a detector that connects to other units in your home. This will ensure that you hear the alarm no matter where you are. Some of the high-end models also connect to your smart home or mobile devices, offering another way for you to stay connected.

Why Trust The Spruce?

This article was researched and written by Katie Begley, a freelance writer specializing in home and family products. Katie has been writing for The Spruce since 2019. All of the carbon monoxide detectors that Katie included monitor for unsafe levels of CO in the home, with special mention made of features that take safety to the next level, such as multiple sources of power or additional smoke monitoring.

Article Sources
The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Carbon Dioxide Health Hazard Information Sheet. United States Department of Agriculture.

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