Updated April 16, 2021 by Will Rhoda

The 10 Best Carbon Monoxide Detectors

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This wiki has been updated 24 times since it was first published in June of 2015. Being odorless and colorless, carbon monoxide is a potentially lethal danger in any home, office, or workplace. But with today's technology, there's practical ways to help keep your employees, colleagues, and family safe from this silent killer. One of these CO detectors will quickly warn you at the first sign of dangerous levels in the air, either with beeping alarms, flashing lights, or both. When users buy our independently chosen editorial picks, we may earn commissions to help fund the Wiki.

1. Nest Protect 2

3. Klein Tools ET110

Editor's Notes

April 13, 2021:

With several interesting new models available on the market and some of our old selections starting to look a bit dated, it wound up being a busy round of updates while we got everything up to speed. During this process, we removed the BRK Electronics CO51120BN due to availability issues, and eliminated the Kidde Digital C3010D and Kidde COPP-B-LPM, believing that better alternatives were available.

We also replaced the First Alert Combination with the First Alert Onelink – which became the second smart-home-ready model we listed, joining the Nest Protect 2 at the top of our list – and we swapped out the X-Sense SC03 for the X-Sense SC07 — an alternate disposable model from the company that, like the SC03, features a 10-year working life, but also includes the helpful addition of a simple LCD that displays current levels in the room. The Chyzghe JSN-999COM and Hydong GS811-A are two well-reviewed, budget-friendly, battery-powered models from lesser known companies that we thought were worth including for those looking for something that’s easy on the wallet. Both models include integrated screens and offer voice warnings in alarm states.

The Klein Tools ET110 is a portable meter that’s recommended for technicians looking for a simple, solid and reasonably affordable tool. Its belt clip makes it easy to hang off your waist or overalls, and it has been drop tested from one meter, which implies a certain level of durability.

We kept a few options like the ET110 mixed into these rankings, hoping that it would make the list more useful for more people, but if you know for sure that what you’re looking for is a field instrument, and not a wall- or ceiling-mounted model for permanent installation, then you might be better off hopping over to our list of carbon monoxide meters.

March 18, 2020:

One of the models on our previous list turned out to be much more of a smoke alarm than a CO detector, and we removed it for safety reasons, to ensure that no one installed it and went about their business under the impression they'd be effectively warned if carbon monoxide levels rose. Safety is of tremendous importance to us in a category like this, so please don't attempt to tamper with sealed detectors, and stay on top of any battery or maintenance issues that arise.

That said, we were able to drum up some exciting additions to our list, including the X-Sense 10-Year, which is a sealed system designed to be installed and to last there for up to a decade without any interference from you. When its cells die, it'll have to be replaced, but 10 years is generally the life cycle of the sensors these devices employ, so it would still be time to replace it, even if its batteries had simply died.

We also added another industrial sensor to the list in the UEI Test Instruments CO71A, that way there'd be something to set against the Pyle Handheld PCMM05, which was the only other portable model we'd included previously. Another portable addition is less intended for professionals as it is people who spend a lot of time in cars, trucks, or even planes, in the Forensics Metal Body Vehicle. It provides a lot of readings in a short time, with frequent notifications when levels are high, but that also drains the batteries more quickly than you'll see in the pro models.

Special Honors

Fluke CO-220 From one of the best-known names in metering equipment, this device is ready for rugged conditions, and boasts a 500-hour battery life, which is made possible in part by its 20-minute auto-off function. Its sensor will typically last for two years. fluke.com

RKI Instruments GX-2009 Able to test for combustible gases, oxygen, carbon monoxide and hydrogen sulfide, this device offers a three-hour charge time and 20-hour battery life. In addition to being compact, its housing sports a rugged build, with an IP67 dust and water resistance and rubber over-molding that's resistant to radio frequency interference. rkiinstruments.com

Calibration Technologies GG-CO This unit is priced much too expensively for most users' consideration, but for those outfitting hazardous-location workplaces, its explosion-proof enclosure may be a must, according to building code. It's backed by a two-year warranty, and has a working temperature range of -4 Fahrenheit to 122 Fahrenheit. ctiengineering.com

4. X-Sense SC07

5. Chyzghe JSN-999COM

6. UEI Test Instruments CO71A

7. Hydong GS811-A

8. Pyle Handheld PCMM05

9. First Alert CO615

10. Forensics Metal Body Vehicle

What Is Carbon Monoxide?

And, yet, it’s toxic to those life forms in a high enough concentration.

A lot have things have been referred to as the silent killer in our vernacular, but few of those killers are as utterly undetectable to the human senses as carbon monoxide. The gas is colorless, odorless, tasteless, and ruthless in its ability to destroy human life. But what exactly is it?

Carbon monoxide consists of equal parts of two building blocks that are essential to life as we know it: carbon and oxygen. Comprised of a single oxygen atom and a single carbon atom, it’s a natural part animal metabolism in the majority of vertebrates and invertebrates alike. And, yet, it’s toxic to those life forms in a high enough concentration.

When carbon monoxide levels rise above 35 ppm, the gas poses a potentially lethal danger to humans and other animals. When you inhale carbon monoxide, you won’t feel it initially. It isn’t like helium, which can immediately alter your voice, or nitrous oxide, which dentists serve up to make you feel giddy while they drill holes in your face. With enough carbon monoxide taking up toxic portions of your breath, you’re liable to feel a little lightheaded and eventually fall asleep. Then, you die. Bummer, right?

The problem begins in the lungs, through which blood flows to drop of carbon dioxide and pick up oxygen. That oxygen binds to your hemoglobin and travels all around the body, invigorating everything from your brain to the muscles that require oxygen to function.

When carbon monoxide enters the lungs, it binds to your hemoglobin in place of oxygen. That means that your blood cells can’t carry that vital oxygen wherever it’s needed. You might not feel this in your muscles as much, but the effects of oxygen deprivation on your brain will be gradual and devastating.

In high enough concentrations, as when you run your car in an enclosed space, the effects are more swift. A smaller, but still toxic concentration, can be even more dangerous, as long-term exposure will usually manifest itself in symptoms akin to the flu, including nausea and mild headaches. Without a functional carbon monoxide detector, not only can these symptoms slowly turn into permanent damage to brain and lung tissue, but others in the vicinity will be susceptible to the toxic gas, as well.

This is why it’s so important to own and regularly check your carbon monoxide detector. It’s a small investment to make in the safety and health of everyone who enters your home.

How Do Carbon Monoxide Detectors Work?

Given the fact that carbon monoxide, even at lethal levels, is undetectable to the human senses, it’s a very good idea to employ a device that can detect it for you. When there’s a fire in the home, you can usually smell or see the smoke just as quickly as your smoke detector can. The advantage of a smoke detector is that it can wake you from sleep in the event of a fire, when your senses are too muted to notice the presence of danger.

Given the fact that carbon monoxide, even at lethal levels, is undetectable to the human senses, it’s a very good idea to employ a device that can detect it for you.

A carbon monoxide detector has to be sensitive enough to detect a much less visible agent, and to do so without creating too many false alarms. After all, the boy who cried wolf eventually asphyxiated on CO2.

Fortunately, carbon monoxide’s propensity to interact with other chemicals and substances (including your hemoglobin) can actually be used to protect you from it. Carbon monoxide detectors usually function in one of three ways. They either utilize silica, chemical solutions, or a reactive gel to register the presence of the gas.

When carbon monoxide comes into contact with a chemical gel substance, the gel’s color changes. Detectors that use gel also often employ photo sensors akin to those found in photoelectric fire alarms. These simple sensors can register the change in gel color, and when they do, they sound the alarm.

Detectors that employ chemical solutions and silica-based detectors both rely on changes to electrical resistance as their triggers. When carbon monoxide interacts with silica, it alters the substance’s electrical impedance, which is monitored by the device’s circuit board. Large enough changes in impedance trigger the alarm. Similarly, small amounts of certain chemical solutions can respond to the presence of carbon monoxide with changes in the flow of electricity through them. Electrodes dipped in the chemical solution detect this change and sound the alarm.

Tips To Maximize Your Safety

In order to keep you and your family as safe as possible, owning a carbon monoxide alarm isn’t quite enough. You should be familiar with how your alarm is installed, as well as what to do if it needs any kind of maintenance. There are also a few additional purchases that can help ensure your safety.

It may take a little up-front cost and planning, but you’ll be grateful if you ever need to use the tools and tactics you’ve acquired.

Carbon monoxide alarms are either plug-in or battery-operated. Detectors that have to be plugged in are dependent on the placement of the outlets in your home for their efficacy. They often also have batteries inside them to act as backups should the power fail. You should routinely test these batteries to make sure you’ll remain safe no matter the power conditions.

Battery-operated carbon monoxide alarms require a little more attention, as you’ll want to keep their batteries as fresh as possible. The benefit of these is that you can install them anywhere, including in a garage that doesn’t have power running to it, to ensure your air is safe to breathe.

If you’re also worried about fire safety, there are combination alarms on the market that can serve both to detect smoke and carbon monoxide. It would also be a good idea to invest in a couple of high-quality fire extinguishers and to keep them in the most effective places, such as the kitchen, or by a fireplace.

Lastly, make sure you and your family have an escape plan in case of a fire or gas leak. This may necessitate the purchase of an escape ladder, as well as the development of a detailed evacuation plan. It may take a little up-front cost and planning, but you’ll be grateful if you ever need to use the tools and tactics you’ve acquired.


Will Rhoda
Last updated on April 16, 2021 by Will Rhoda

After deciding that the pen was mightier than the pliers, Canadian electrical contractor William Rhoda abandoned his career and headed back to college, where he majored in marketing and advertising and won a scholarship along the way to earning a diploma in creative communications. His past career landed him a depth of knowledge in tools and hardware, while his current career schooled him in audio, video and camera equipment. During his leisure time, he’s learned lots about outdoor gear, and years of tiresome backyard maintenance have taught him all about pools and hot tubs. His recreational pursuits include rest, relaxation and revolutionary action, and his roommate’s a hairless cat.


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