The 6 Best Carbon Monoxide Alarms of 2019

Shop for the best carbon monoxide alarms from brands like First Alert and Nest

Our editors independently research, test, and recommend the best products; you can learn more about our review process here. We may receive commissions on purchases made from our chosen links.

Our Top Picks

Best High-End: Nest Protect Alarm at Amazon

“Connects to your smartphone to give you immediate updates.”

Best Overall: Kidde Nighthawk Plug-In at Amazon

“Able to detect both high and low levels of carbon monoxide.”

Runner-Up, Best Overall: First Alert OneLink at Amazon

“Reviewers say this reasonably priced model is reliable and accurate.”

Best Budget: Kidde KN-COB-B-LP2 Alarm at Amazon

“Uses the same electrochemical sensor as pricier units for a dependable read.”

Best Design: Elvicto Combination Alarm from Amazon

“Sleek, easy-to-install, and incredible battery life.”

Best Portable Unit: Pocket CO KWJ 72-9021 at Amazon

“Touted as the world’s smallest, renewable carbon monoxide detector.”

  • 01 of 06

    Best High-End: Nest Protect Smoke & Carbon Monoxide Alarm

    Nest Protect Smoke & Carbon Monoxide Alarm, Battery (2nd gen)
    Courtesy of

    If it’s bells and whistles you’re after, the Nest Protect is the carbon monoxide detector for you. The Nest is actually a combination smoke and carbon monoxide detector that connects to Wi-Fi and alerts your smartphone or tablet if there’s a problem. It comes in hard-wired or battery-powered versions and should be mounted to the wall or ceiling. Most importantly, it works well, notching above-average marks for detecting high and low carbon monoxide levels as well as accurately reporting them.

    The Nest has a ton of features: Like the First Alert OneLink, it links to other Nests and can tell you where a problem is both audibly and with phone alerts. You can even use your phone to “hush” the alarm, which periodically tests itself for proper power and operation. Nest even acts as a nightlight, lighting up as users walk under it when it’s dark, and connects to other Nest products such as the Nest Thermostat and Nest Cam. Despite all of this technology, users say it’s easy to set up. They also say the units are attractive, and they love getting phone alerts instead of middle-of-the-night low-battery chirps. As with all Wi-Fi devices, some reviewers say they’ve had problems keeping their Nests online. It’s backed by a two-year warranty.

  • 02 of 06

    Best Overall: Kidde KN-COPP-3 Nighthawk Plug-In Carbon Monoxide Alarm

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

    If you don’t need a dual-function carbon monoxide and smoke detector, check out the Kidde Nighthawk KN-COPP-3, which plugs right into a standard outlet. This carbon monoxide detector gets top marks for detecting high levels of carbon monoxide and very good ones for detecting lower levels. Display accuracy is good, though not top-notch like the First Alert. Though this is a plug-in unit, it includes a 9-volt battery backup to keep working during power outages.

    Features on this Kidde include an LED display, a level button that lets users see the peak carbon-monoxide level detected since the last reset, a sensor-on indicator, and a test/reset button. A 6-foot power cord allows it to be displayed on a table or shelf, too. Unlike the First Alert, it doesn’t link to other units, and one should be placed on every floor of the house. Users love how exceptionally easy to use this installation-free alarm is, though some warn that they were shipped older units. It’s backed by a five-year warranty. 

  • 03 of 06

    Runner-Up, Best Overall: First Alert OneLink SCO501CN-3ST Smoke and Carbon Monoxide Alarm

    First Alert SCO501CN-3ST ONELINK Battery Operated Combination Smoke and Carbon Monoxide Alarm with Voice Location
    Courtesy of

    When it comes to carbon monoxide alarms, reliability and accuracy are the most important buying criteria. Reviewers say this reasonably priced First Alert OneLink model, a combination smoke and carbon monoxide alarm, has both in spades. It uses electrochemical sensors that get top marks from experts for recognizing both high and low carbon monoxide levels, and testers say it has a very accurate display. This is a ceiling-mounted alarm that requires two AA batteries. 

    As a OneLink device, this model wirelessly connects to any other First Alert OneLink devices in the home, triggering all other alarms as well. Other features include a voice alarm with 11 programmable locations to tell users where an alarm was triggered, an 85-decibel siren, a test/silence button, and indicator lights for both smoke and carbon monoxide. Owners say these units are easy to set up without expert help, and they especially like them for protecting larger homes. Some reviewers say they have had issues with false alarms or the units not linking properly, however. Warranty is seven years.  

  • 04 of 06

    Best Budget: Kidde KN-COB-B-LPM Carbon Monoxide Alarm

    Kidde KN-COB-B-LPM Carbon Monoxide Alarm
    Courtesy of

    A bare-bones carbon-monoxide protector like the Kidde KN-COB-B-LPM will still do its job, so if you don’t have a lot of money to spend, don’t fret. It uses the same electrochemical sensor as pricier units and can be either mounted on the wall or left free-standing on a table or shelf. It does not plug into the wall and requires three AA batteries to use.

    This Kidde has two indicators: One to reassure users that the sensors are working, and another to alert them that the alarm has sounded. There is a test/reset button and low-battery signal as well. A battery lockout system means owners won’t be able to shut the battery compartment unless all batteries have been properly installed – great for preventing absent-minded slip-ups. Reviewers love how compact and easy to use these alarms are, and few report false alarms or any other issues. It’s backed by a five-year warranty.

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  • 05 of 06

    Best Design: Elvicto Combination Smoke Alarm Carbon Monoxide Detector 

    Sleek, easy-to-install, and designed for both smoke and carbon dioxide detection, the advanced Elvicto Combination Smoke Alarm Carbon Monoxide Detector is a high-caliber, high-tech product. Consumers praise this device’s 2-in-1 functionality, compact size, and efficient design.

    Thanks to its ultra-sensitive photoelectric sensors, the Elvicto will alert you in seconds in the event of CO-related danger. Bright green and red LED lights are very visible and indicate normal operation. Plus, the product comes with a sealed-in lithium battery that enables it to last 10 years or more. It will provide your family with secure, long-lasting protection so that you don’t have to worry about the risk of carbon monoxide exposure.

  • 06 of 06

    Best Portable Unit: Pocket CO KWJ 72-9021 Carbon Monoxide Detector

    In terms of size and functionality, nothing beats the Pocket CO KWJ Carbon Monoxide Detector. Touted as the world’s smallest renewable carbon monoxide detector, this stylish, pocket-size device boasts an easy-to-read digital display, an 85 db alarm that blinks a bright red light, and sophisticated, one-button operation, all of which renders the Pocket CO super-simple to use.

    Small enough to fit on a keychain and take with you, but still just as effective as a standard-sized carbon monoxide detector, the Pocket CO Detector is both unobtrusive and functional. Users love that this lightweight, portable device fits in the palm of your hand while providing reliable protection.

Products Tested by

How We Tested

We bought a top-rated carbon monoxide alarm that our reviewer tested for weeks on end. We asked our tester to consider the most important features when using this carbon monoxide alarm, from its detection capabilities to its interconnectivity. We’ve outlined the key takeaways here so that you, too, know what to look for when shopping.

What to Look for in a Carbon Monoxide Alarm

Smoke detection The first choice you’ll want to make is whether you want a product that’s both a smoke and carbon monoxide detector. If you already have smoke detectors in your house, it will probably be less expensive to simply buy supplementary CO alarms. However, if you’re in the market for both, you can cross two items off your to-do list with 2-in-1 units.

Installation Do you want an alarm that’s plugged into an outlet, battery-powered, or hardwired? Battery-powered units can be placed anywhere, but you’ll have to stay on top of their battery status. Plug-in products won’t die on you, but you’re limited in where you can put them. Hardwired units, on the other hand, require more complex installation.

Interconnectivity Many 2-in-1 CO and smoke detectors can be interconnected, meaning if an alarm goes off on the first floor of your home, it will trigger the alarms on the second floor as well. This ensures you won’t ever miss the alarm. However, if the alarm you choose can’t be interconnected, you will have to buy numerous units to cover your entire home.

Test Results: Nest Protect Smoke & Carbon Monoxide Alarm (Best High-End)


What We Like

  • Connects to smart devices

  • Early warning system

  • Auto-testing and automatic battery monitoring

What We Don't Like

  • Pricey

Nest Protect Smoke & Carbon Monoxide Alarm
The Spruce
Nest Protect Smoke & Carbon Monoxide Alarm
The Spruce
Nest Protect Smoke & Carbon Monoxide Alarm
The Spruce

Our tester loved this device for its “loud and audible” alarms, smart device app integration, easy setup, and motion-sensor night light. He reported, “The device uses a constantly-updating carbon monoxide detection algorithm, checks its own battery level 400 times a day, and quietly tests its speaker and horn once a month via Sound Check.” And while it is an expensive unit, our reviewer felt it was worth the investment. “Simply put, Nest has made one of our most essential home products into a smart, user-friendly, and intuitive device,” he declared.