The 8 Best Carbon Monoxide Detectors of 2024

Best Overall

Kidde Nighthawk Plug-In Carbon Monoxide Detector

$38 at Amazon $65 at Wayfair $43 at Home Depot

The Kidde Nighthawk has one purpose: to monitor for dangerous levels of carbon monoxide. It doesn’t include a smoke detector function, which was our biggest point of concern. However, we think it’s an ideal choice if you’re specifically looking for a carbon monoxide detector and already have hardwired smoke detectors in your home. We found it easy to use and reliable, earning it our top recommendation for a carbon monoxide alarm.

This plug-in model requires no electrical know-how and takes up just one standard outlet. Once it powers on for the first time, it lasts 10 years before signaling it's time for a replacement. A 9-volt battery backup gives you confidence that the Kidde Nighthawk keeps monitoring for carbon monoxide, even if there is a power outage. 

The Kidde Nighthawk also stands out for having a simple interface. It has just two buttons: for testing the unit and to recall peak levels of detected carbon monoxide (CO), measured in parts per million (PPM). The digital display is a helpful feature not always found on carbon monoxide detectors. It provides a reading of current CO levels and is helpful for interpreting the beeps that the device may emit.

The intermittent pattern of the alarm—four beeps, followed by 5 seconds of silence—may not immediately grab your attention. However, it is loud enough that we feel confident it would wake most people while sleeping. We found that the volume gets your attention. When we tested, there were children in another room who were on high alert once the alarm started sounding.

Carbon monoxide detectors should always be placed in or within 10 feet of any sleeping area. With this parameter in mind, the Kidde Nighthawk is an excellent choice. 

_{Dimensions: 6.06 x 3.75 x 1.75 inches | Power Source: Plug-in, with 9-volt battery backup | Smoke Detector: No | Warranty: 10 years}

Best Value

First Alert Battery-Operated Carbon Monoxide Detector

$22 at Amazon $37 at Wayfair $30 at Walmart

We think a carbon monoxide detector is a small investment towards peace of mind. A basic model, like the First Alert CO400, continuously monitors for harmful levels of carbon monoxide and sounds the alarm if such a condition develops. Besides the audible 85-decibel alarm, a flashing LED also provides a visual indicator of danger. 

The First Alert Battery-Operated Carbon Monoxide Detector uses a proven form of detection in the form of an electrochemical sensor. The unit is powered only by a 9-volt battery, so you’re not limited on where to place the carbon monoxide detector because of outlet proximity or electrical wire connections.

While this product represents a good value, it’s worth noting that it should be replaced every 5 years, while some other models offer a 10-year life expectancy. An end-of-life signal chirp and low-battery beep round out the features of this simple unit. 

_{Dimensions: 3.4 x 1.5 x 5 inches | Power Source: 9-volt battery | Smoke Detector: No | Warranty: 5 years}

Best Plug-in

Kidde Carbon Monoxide Detector, AC Plug-In

$25 at Amazon $32 at Home Depot $25 at Walmart

A plug-in carbon monoxide detector offers a simple solution to protecting yourself against harmful levels of this poisonous gas. The Kidde KN-COB-DP2 Carbon Monoxide Detector is fast to install—just plug it into a standard electrical outlet. This model has a 10-year life span that surpasses the 5- or 7-year life expectancy of some other plug-in carbon monoxide detectors. 

Like most similar products, this Kidde model includes a battery backup for uninterrupted monitoring, even if the power supply is interrupted. It requires two AA batteries, which you may be more likely to have on hand than the 9-volt battery backup some other plug-in carbon monoxide detectors require.

Whether the unit is running on electricity or battery power, an 85-decibel alarm sounds if it detects carbon monoxide levels exceeding safe levels. This basic model lacks a digital display, so you need to consult the owner’s manual to learn what the small color-coded light signals mean. The light glows green during normal operation, but turns red because of an alarm, low battery power, or the end of the unit’s life span. 

_{Dimensions: 2.75 x 1.5 x 4.5 inches | Power Source: Plug-in, with AA battery backup | Smoke Detector: No | | Warranty: 10 years}

Best Smart

Google Nest Protect Smoke & CO Alarm

$149 at Home Depot $119 at Walmart View on Lowe's

A smart carbon monoxide detector integrates with your existing smart home setup to keep you informed and protected. Google’s popular Nest smart home ecosystem offers an easy-to-use carbon monoxide detector that monitors for dangerous levels while staying alert to smoke from smoldering fires or flames.

It’s intelligent enough to alert you to low levels of smoke (such as from high-heat cooking) without blasting the alarm. You can silence the Nest Protect alarms within the app, giving you convenience and control on your smartphone. 

There are plenty more user-friendly features built into this smoke and carbon monoxide detector that integrates with Google Assistant, but the safety benefits are the most important. While virtually all carbon monoxide detectors include a testing function, it’s easy to skip out on actually performing a test to ensure that your unit is operating properly.

The Nest Protect is designed to silently test its batteries and sensors more than 400 times each day. Once a month, it tests the audible alarm functions by sounding the speaker and horn within the unit. Before bed each night, you see the light ring around the center of the unit turn green to indicate that the battery level is sufficient and assure you won’t be woken up to an unpleasant low-battery alarm.

If smoke or carbon monoxide levels become dangerous, the device alternates between an audible alarm and a voice alert specifying where the problem originates from. The center ring of the Nest Protect also glows red to give you a visual indicator there is an emergency. 

Nest Protect is available as a battery-operated or hardwired unit. Although our tests found that the battery version is a breeze to set up, we prefer the hardwire option because all the features and functions of this smart carbon monoxide detector can drain battery power. It’s not surprising that the battery version requires 6 AA cells. (The hardwired version needs 3 AA batteries for its backup power system.)

The sensors inside this combo smoke and carbon monoxide detector have a 10-year life span, which is good to know if you’re installing smoke detectors in a state that regulates the life expectancy of home smoke detectors. However, it’s worth noting that the manufacturer’s warranty on the unit is only valid for 2 years. 

_{Dimensions: 6.22 x 2.76 x 6.26 inches | Power Source: Battery or hard-wired | Smoke Detector: Yes | Warranty: 2 years}

Best Hardwired

First Alert Hardwired Carbon Monoxide Detector

$35 at Amazon

A hardwired carbon monoxide detector integrates into your home’s electrical system, freeing up an outlet and eliminating frequent battery replacement. The First Alert CO5120BN is a basic mounted carbon monoxide detector that we recommend because it can connect with up to 18 other First Alert devices, and it includes a 9-volt battery back-up. Both are important safety considerations to ensure you're notified if carbon monoxide reaches dangerous levels. 

The First Alert CO5120BN's electrochemical sensor detects carbon monoxide levels over 30 parts per million. (Symptoms become more noticeable over 70 ppm.) When the concentration exceeds safety thresholds, it triggers an 85-decibel alarm.

The only other warning is a small red light, which flashes in a special pattern when the detector is triggered. The light keeps flashing, even when CO drops below hazard levels. So you need to manually clear the latching alarm by testing the unit. 

_{Dimensions: 5.53 x 2.09 x 5.72 inches | Power Source: Hardwired, 9-volt battery backup | Smoke Detector: No | Warranty: 10 years}

Best with Smoke Alarm

Kidde Battery-Operated Smoke/Carbon Monoxide Alarm

$61 at Amazon

A combination carbon monoxide detector can efficiently protect your home and family from harmful gas leaks and alert you to fire danger. The Kidde Smoke & Carbon Monoxide Detector is about the same size as an average smoke detector, but includes an electrochemical sensor to detect carbon monoxide.

If an detector is triggered, this model clearly announces: “Warning carbon monoxide” or “Fire.” If a low-battery alarm is initiated, the voice announcement makes that clear, too. 

This combo smoke and carbon monoxide detector uses 2 AA batteries. It’s rated for 10 years of use, making it compliant even in states that require a 10-year lifespan for smoke detectors.

It’s also worth noting that the Kidde Smoke & Carbon Monoxide Detector uses an ionization sensor, which is likely to register a fast-burning fire more quickly than a product using a photoelectric sensor to detect flaming and smoldering fires.

During our in-home testing, we accidentally set off the smoke alarm while cooking, but the Smart Hush feature on this device silences the alarm for 8 minutes if this happens, giving you time to clear the smoke from the kitchen or from an extinguished candle. 

_{Dimensions: 5.6 x 5.6 x 1.8 inches | Power Source: 2 AA batteries | Smoke Detector: Yes | Warranty: 10 year}

Best Battery-Powered

First Alert Carbon Monoxide Detector

$41 at Amazon $55 at Wayfair $39 at Walmart

If you’re looking for a carbon monoxide detector with versatile placement options, consider a battery-powered unit. The First Alert CO710 Carbon Monoxide Detector doesn’t need to be hardwired to your home’s electrical system or plugged into an outlet. Instead, it operates on power supplied by a long-lasting lithium-ion battery.

This makes it a good pick if you’re looking for a portable carbon monoxide alarm for use while traveling. Many battery-powered carbon monoxide alarms operate using AA or 9-volt batteries that require occasional replacement.

However, this popular model from First Alert comes equipped with a lithium-ion battery that is designed to last for the 10-year life span of the unit. The long-lasting battery ensures that the carbon monoxide detector stays on alert at all times, as well as powers the digital display. 

Some display features worth noting include that it displays CO in parts per million, along with a graphical rendition of the relative concentration level. A peak CO memory function also notifies you of the highest detected levels. It even includes an ambient temperature reading which, frankly, adds no functionality but is nice to have.

_{Dimensions: 4.75 x 2.63 x 0.94 inches | Power Source: Lithium-ion battery | Smoke Detector: No | Warranty: 10 years}

Best Interconnected

Gentex Hardwired Interconnect CO Alarm

$40 at Home Depot

Installing multiple carbon monoxide detectors is a wise choice, especially in large homes or if you have multiple sources of potential gas leakage such as a dryer vent and gas hot water heater. By choosing an interconnected carbon monoxide alarm, you can monitor for the presence of this deadly gas and hear an alarm from all devices, even if only one device detects CO. 

The Gentex CO1209 carbon monoxide detector, designed for residential or commercial settings, has a basic, utilitarian design that makes testing and monitoring the unit simple. Also, its tamper-resistant design makes it a good choice for rental properties. 

This hardwired carbon monoxide detector can interconnect with other Gentex devices equipped with the brand’s Dualink technology. In the event of a power outage, it remains operational with the help of a 9-volt battery backup. A self-test button on the front of the unit ensures that it’s working properly.

It only has a 5-year lifespan, so you have to replace the unit more often than similar products. But it has a reputation for offering reliable performance with few false alarms. 

_{Dimensions: 6.25 x 6.25 x 1.8 inches | Power Source: Hardwired | Smoke Detector: No | Warranty: 1 year}