Best Carbon Monoxide Detector for 2024 - CNET

Article updated on September 23, 2024 at 9:02 PM PDT

Carbon monoxide is known as a silent killer and presents a real danger, so you'll want to monitor the CO levels in your home. We found the best carbon monoxide detectors to keep your family safe.

CNET’s expert staff reviews and rates dozens of new products and services each month, building on more than a quarter century of expertise.

CNET’s expert staff reviews and rates dozens of new products and services each month, building on more than a quarter century of expertise.

Carbon monoxide is commonly known as the "silent killer" -- a gas that can spread through your home without any color, odor or even taste to alert you to danger. As for why it's a 'killer,' breathing in carbon monoxide can restrict the amount of oxygen carried throughout your blood and cause breathing difficulties. This is why you should take the threat of carbon monoxide in your home seriously and why a reliable carbon monoxide detector is critical for ensuring your safety and that of your family.

In its early stages, carbon monoxide poisoning can lead to headaches, nausea, dizziness and general weakness and, if not treated, can be fatal. It's easy to confuse it with flu, too, making it important to have a carbon monoxide detector in your home. You don't want to risk CO poisoning with an old or defective monitor. Whether you're a new homeowner or it's time to replace your existing detector, we found the best, most reliable models to help ease your mind and protect your home.

A carbon monoxide detector is necessary to help protect your household from this potentially deadly gas. The detector can alert you to dangerous levels of carbon monoxide and give you time to evacuate and, if necessary, seek medical attention.

All carbon monoxide detectors share the same basic function, though they may vary in efficacy, and additional smart features like digital displays or emergency notifications to your smartphone, as well as doubling as a smoke detector in some cases.

To help you get the best carbon monoxide detector, we put a number of popular models to the test, evaluating their ability to detect carbon monoxide at two hazardous concentration levels: 250 and 400 parts per million. Here are the best options for keeping you safe.

At an average retail price right around $35, the CO615 from First Alert is the perfect carbon monoxide detector if you're looking for handy features and decent performance at an affordable price.

Highlights include a digital display that shows real-time carbon monoxide concentration in ppm and battery level, a test/silence button for weekly testing and a peak carbon monoxide level button to show the highest carbon monoxide concentration detected. This is a plug-in model that is backed up by two AA batteries (Energizer E91 only). Just pick any outlet that's not controlled by a switch or dimmer, and that is at least 5 feet away from any fuel-burning appliance. Plug it in and you're ready to go. The unit can be hung in the wall with two screws and its cord extends at least 6 feet, giving you a little flexibility as far as where exactly you can install it in your home.

This unit ranked third in our quickness of response test. On average, it took a little more than 12 minutes to detect the presence of carbon monoxide at 250 ppm and just over 8 minutes to detect carbon monoxide at 400 ppm. The real-time carbon monoxide reading is pretty accurate, taking only two and a half minutes to catch up to the reading shown in our control device. The carbon monoxide reading on the detector went a little above what our control was showing. The discrepancy between the two readings remained below 7%.

Having a real-time display of the carbon monoxide concentration is incredibly useful. Most common carbon monoxide alarms are designed to go off after the carbon monoxide levels in an area have been above a certain threshold for a while. Having immediate and accurate access to this information can help you take swift preventive action before the alarm has a chance to react.

If all you need is a carbon monoxide detector that can reliably watch your back without leaving a hole in your pocket, then the First Alert CO400 is perfect for the task. Basic features include a single test/silence button and a very loud alarm. It doesn't come with a digital display or any smart features, but it makes up for what it lacks in fancy looks with performance and affordability. Typically available for $25 or less, the CO400 was the least expensive carbon monoxide detector we tested, and it was also the fastest at detecting carbon monoxide at both concentration levels. At 250 ppm, its alarm was set off after an average of 10 minutes, 46 seconds and at 400 ppm, it took only 7 minutes, 3 seconds. Those are excellent results, regardless of price.

With its low asking price, the CO400 would also be a particularly good pick for multistoried homes, where you should aim to have at least one detector on every floor. Plus, as a battery-powered model, it won't add to your energy bill and is immune if you have a power outage.

Some carbon monoxide detectors can find both carbon monoxide molecules and smoke particles. These are called "combo" or "two in one" units, doubling as smoke detectors. The First Alert Onelink 1042136 stood out in this category. This device got second place in our quickness of response test, detecting carbon monoxide at 250 ppm after only 11 minutes, 42 seconds and, similarly, carbon monoxide at 400 ppm after 8 minutes, 10 seconds.

Despite not having a digital display, the voice alarm will speak to you in English and clearly state the current carbon monoxide concentration. Depending on where you installed your device, it can also tell you the exact location of the emergency. For example, during testing, you could hear the device saying: "Evacuate, evacuate. There's carbon monoxide in the living room, 265 ppm." To my surprise, the control device reading for this round was 260 ppm. That amounts to an accuracy error of less than 2%, which is significantly better than anything else we tested.

Additionally, Onelink is a compelling option for those seeking smart functionality. It's compatible with Google, Apple HomeKit and Alexa. All you have to do is download the Onelink Home app and create a free account. Then, follow the instructions to set up a new device. From the app, you can test or silence your carbon monoxide alarm, interconnect other carbon monoxide detectors in your home and get emergency notifications to your smartphone.

All of that said, there are two caveats worth mentioning here. First is the cost. Often selling for more than $100, the Onelink combo detector is an expensive option, particularly if you're shopping for more than one in something like a multistory home. On top of that, while it performed well in our carbon monoxide tests, it was less impressive when we compared it to other smoke detectors, taking over a minute to detect a controlled, slow-smoldering fire nearby. While not disqualifying, that was still almost twice as long as it took other combo detectors to react.

To put these detectors to the test, we took to the lab and built a test rig designed to measure each unit's response time to varying concentrations of carbon monoxide, specifically at 250 ppm and 400 ppm. Our goal was to determine each detector's respective effectiveness at detecting potentially hazardous levels of carbon monoxide. To declare our winners, we also took into account features that add to the overall user experience, performance and cost-efficiency of each unit.

For the 250 ppm concentration level, we try to simulate a situation where carbon monoxide has begun to build up to hazardous levels. We test twice at this concentration and average the results. At 400 ppm, we replicate a worst-case scenario, a potentially deadly situation, and give the units a pass or fail score. Spoiler alert: They will all save your life, which goes to show how important it is to have carbon monoxide detectors installed on every floor of your home.

Our custom-built carbon monoxide detector test station. It's one of the deadliest things we've ever put together in our product testing lab.

This is one of the most dangerous tests we've ever conducted. Carbon monoxide exposure is no joke. It's virtually undetectable and, well, quite deadly. We needed to create a safe way of testing carbon monoxide detectors without risking the health and safety of our laboratory staff. So I made use of my rudimentary carpentry skills and built a carbon monoxide detector test station. Its components are:

Carbon monoxide detector chamber -- made using wood, plexiglass, silicon, tape and a bunch of finish nails.

Carbon monoxide tank with gas flow regulator -- cylinder tank containing carbon monoxide at 2,500 ppm and balance air.

Testo 300 with carbon monoxide Ambient sensor -- our control device for this experiment.

Two portable carbon monoxide gas alarms.

A look at the interior of CNET's carbon monoxide detector test rig.

The chamber houses two carbon monoxide detectors, a) the CO Ambient sensor portion of our control device, the Testo 300, which is a combustion analyzer used by heating engineers who carry out installation and routine maintenance of industrial and residential heating systems, and b) the unit under test, or UUT, which takes the place of each carbon monoxide detector we tested for you. The chamber is sealed with foam but not air-tight, since we're not particularly interested in making a carbon monoxide bomb.

We use a portable carbon monoxide alarm on the gas regulator to keep a nose out for leaks.

We installed a gas flow regulator on our tank to avoid pressure spikes, followed by a gas line to feed our gas mixture into the chamber. Two additional portable carbon monoxide detectors are used. One near the valve, to ensure there are no leaks and another that must be worn by the person experimenting to make sure there is no carbon monoxide buildup in the test station area. On top of all that, our respirator suits and amply ventilated location ensure that we get a constant stream of fresh air at all times. This might all sound excessive, but it's always good laboratory practice to put safety first, especially when you're dealing with such a stealthy and prolific killer.

We start by feeding our gas mixture to the chamber and closely monitoring the carbon monoxide concentration on the Testo. Once the concentration inside our chamber reaches at least 250 ppm or 400 ppm, we stop feeding the gas and start a timer. We want to assess how long the carbon monoxide detectors take to react to those conditions. As you may understand, we wanted to limit our exposure while making sure our results were repeatable.

Our results are summarized in the interactive graph below:

Nest Protect smoke and carbon monoxide alarm: A very compelling option for those who don't mind spending a little more in exchange for a wide range of smart features including location-specific voice alarm, color-coded emergency notifications and smartphone app control for silencing and routine testing. It underperformed its competition in our quickness of response test, with a bottom-three result in the 250 ppm run and last place in the 400 ppm run. Fortunately, it did a better job at quick smoke detection and fire hazards during our most recent round of smoke detector tests.

Kidde KN-COPP-B-LPM battery-operated carbon monoxide alarm: Battery-powered (meaning monitoring won't stop in a power outage), digital display, test/reset and peak carbon monoxide buttons, visual cues for alarm and operational status. Great unit if you want an affordable device that is capable of monitoring real-time carbon monoxide levels as well as battery life. Not the fastest at detecting carbon monoxide (it ranked fourth). Carbon monoxide readouts on its screen are the least accurate of the bunch, at 15% error, which is by no means the end of the world.

X-Sense combination smoke and carbon monoxide alarm: This combo unit comes equipped with a 10-year sealed lithium battery and a digital display that shows real-time carbon monoxide concentration, battery level and working status. Second-to-last place in our quickness of response test, detecting carbon monoxide at 250 ppm after 20 minutes. The carbon monoxide concentration monitor is accurate, with less than 5% error. Its LCD is smaller than those of other products in this category, which makes it a little hard to interpret the readouts if you're not close to the device.

Kidde Plug-in KN-COB-DP2 carbon monoxide alarm: A plug-in unit, backed up by two AA batteries. Features a single LED indicator and a test/reset button. Very specific brand and model requirements for battery replacements. The unit does not come with a cord extension so its installation placement is limited to an electrical outlet. Last place in our quickness of response test.

Eton's new Blackout Buddy plugs into your wall and includes a carbon monoxide alarm system as well as an emergency flashlight that will automatically flip on should your power go out.

Carbon monoxide detectors work differently than smoke detectors and should have different sensors. Getting the properly equipped CO detector is vital for monitoring levels in your home to prevent any kind of potential poisoning. Ideally you want a detector with an electrochemical sensor as this type tends to handle changes in temperature and humidity variations best. It also does a good job at not reacting to typical household chemicals and odors that could improperly trigger an alarm.

Many carbon monoxide detectors have a sealed battery and can last years before needing to be replaced. While this is great as a set it and forget it type of situation, but it can also lead to forgetting to ensure it is working. When shopping for a CO detector, make sure the options you are considering provide some kind of alert when it is time to replace the device.

This smoke and carbon-monoxide detector works over WiFi to speak to other smoke detectors in your house. Accessed via a smartphone app, Nest Protect also reports emergencies when you're not home.

As I mentioned in the previous section, many carbon monoxide detectors are battery powered, which can be good since you won't have to rely on placing it near an outlet or dealing with electrical wiring. A battery-operated unit also means that should your home lose power, your CO detector will still be working. However, a hardwired detector has the benefit of never worrying if the battery has died and can sometimes offer more features since power supply isn't a major concern.

Carbon monoxide detectors work by using sensors to detect the presence of carbon monoxide in the air. When carbon monoxide levels reach a certain threshold, the detector sounds an alarm to alert occupants of the building. There are different types of detectors available, but most use electrochemical sensors, metal oxide semiconductors or biomimetic sensors to detect carbon monoxide.

Carbon monoxide detectors should be placed on every level of the home and in every sleeping area. They should also be placed near sources of potential carbon monoxide, such as furnaces, water heaters, fireplaces and attached garages. Follow the manufacturer's instructions for the specific placement of your detector.

Carbon monoxide detectors should be replaced every five to seven years, depending on the manufacturer's recommendations. Regular testing and maintenance are also important to ensure that the detector is functioning properly and providing adequate protection.

Never ignore carbon monoxide alarms. If your carbon monoxide detectors go off, evacuate the building immediately and seek fresh air. Call the fire department or emergency services from a safe location, and do not re-enter the building until it has been checked and declared safe.