Carbon Monoxide Detector Buyers Guide

Carbon monoxide detectors are electronic devices that sense the concentration of carbon monoxide in the air. There are many different detectors on the market, but fundamentally, they are all similar. They consist of a sensor that detects CO, the electronics to control and report the results, a power source to keep it working, and a package to house all of this.

In deciding which product to buy, however, the subtle differences between the products become hugely important. In this carbon monoxide detector buyers guide, we will look at some features to consider when making a buying decision. We will look at the various choices for each feature and tell you which one we favor. We have made a point of reporting on our product pages the following features for each product. You, of course, have the final say. Only you know what features will be required in your particular situation.


1. UL or CSA Listed Product

Many places in the US and Canada have codes that require that UL- or CSA-approved detectors be installed in residential situations, with more jurisdictions UL Listed logorequiring them all the time.  If you live in one of these places, you must install one or more of these detectors in your home. (For more information about number and placement of CO detectors, see our page “CO Detector Placement“.) Be very careful when shopping, because many of the cheapest detectors being sold are not UL/CSA listed.  Some may even say they comply with the UL/CSA standard, but if they’re not listed, they won’t cut it.CSA logo

If you aren’t required to use “approved” detectors, or you’re looking to use your CO detector in non-residential situations, then UL/CSA approved devices are not required. They may also not be desired, since the “approved” devices really don’t do a very good job of protecting you against low level carbon monoxide poisoning (see this graphic ).


2. Low Level Detection and Alarming

Many people are sensitive or susceptible to low levels of carbon monoxide exposure, which we are defining to mean less than 30 ppm. They suffer symptoms of this exposure much sooner than healthy adults would (more here ). To adequately protect these at-risk people, carbon monoxide must be detected and reported at much lower levels than the “approved” devices will (see UL/CSA alarm levels here ).

There are many detectors available that detect CO at low levels, display the ambient concentration in real time, and produce alarms that alert you if unsafe levels are reached or surpassed. By their very nature, they do not meet UL and CSA standards, and never will unless the UL and CSA lower their alarm thresholds to protect at-risk people.

You always have the option of acquiring and using low level carbon monoxide detectors. We highly recommend that you do so if you or your loved ones are at risk. If you live in a place where “approved” detectors are required, these low level devices will supplement rather than replace the UL/CSA devices. In such cases, we recommend you buy the cheapest UL/CSA devices you can, as the low level detectors will be doing the heavy lifting.

3. Operating Environment Limitations

Carbon monoxide detectors are built for different uses and different environmental conditions. The manufacturer specifies the conditions under which they expect and warrant their product to operate. These conditions include temperature, humidity, water, dust, chemicals and solvents, vibration, shock, corrosive environments, and so on.

All CO detectors can tolerate conditions that humans find acceptable to live in (your home). However, if you plan on using a CO detector in conditions which may exceed a typical home environment, you should pay close attention to the product specifications. If you operate a detector outside of its specified range, you may void the warranty.

4. Digital Display of CO Concentration

All of the carbon monoxide detectors we recommend on this site have audible and visual alarms that will alert you to an unsafe level of CO being detected. Many of them have a digital display that shows the level of CO being detected in Parts Per Million (ppm) as well. A display extends the usefulness of a CO detector, but not all displays work the same.

Ideally, you would like to know the actual level of carbon monoxide present in real time. Digital Display LLSome of our products can display this information starting at 1 ppm. Most of the devices, however, have a threshold, over which they start showing the CO level, usually 10 ppm. UL/CSA listed detectors are not allowed to show the ambient level until it reaches 30 ppm.

All of the detectors with a display we feature have a button that, when pushed, will show you additional information. Most of the detectors will display the peak level of CO that has been detected by the device since it was last reset. Some devices display even more, including current ambient level, duration of peak reading, and dosimetry. This additional information can dramatically increase the usefulness of the detector displaying it.


5. Alarm Levels and TypesSensorcon CO Inspectorkidde ultra-sensitive KN-COU-B

Each carbon monoxide detector on this site is designed to alert you to an unsafe level of CO being detected. All of them have an audible horn and one or more flashing LEDs to report this condition, and two of them even have a vibrator like a cell phone. However, the  levels at which they report an alarm vary widely from one product to the next.

All of the UL/CSA listed detectors are uniform in the levels at which they produce an alarm (details here). The non-UL/CSA detectors have varying response levels, and these alarm points will be described on our products pages for each device.


6. Power Source

Being electronic devices, carbon monoxide detectors need electrical power to operate. There are four different kinds of power sources used in the detectors on this site. These power sources are: replaceable batteries, non-replaceable batteries, plug in to receptacle with battery backup, and hard-wired. Each of these power sources has its pros and cons, so let’s take a look.


Replaceable Batteries:

Some UL/CSA listed detectors AA alkaline batteries, and they might need to be replaced several times during the life of the product. The problem is, the batteries can be removed or die, rendering the detector useless. As the batteries get low, the device will sound an alarm (if you’re around to hear it). A CO detector with dead or missing batteries is simply wall art, and all occupants are at risk. There are many cases where carbon monoxide poisoning occurred for this very reason. We, therefore, do not recommend any detectors with replaceable batteries.


Non-Replaceable Batteries:

These batteries are long-lived lithium units that are permanently installed in the detector. They should power the device until the sensor reaches its end of life, although they may not. Low batteries are reported by a distinct alarm, so you’ll know when you need to replace the detector. Because these batteries can’t be removed, there is less danger of the device being rendered inoperable.


Plug In to Receptacle with Battery Backup:

These detectors get most of their power from a receptacle, and they should never be plugged into one that can be turned off by a switch. If the power goes out in the home, a 9v battery automatically kicks in to power the unit until the power is restored. If the 9v battery gets low, dies, or is removed, the device will sound a unique alarm to alert you to this fact (if the power is on). Since these detectors are usually operating on 120 vac power, they are not particularly efficient, and extended operation on the battery alone will wear out the
battery quickly. It should be replaced after every power outage. One last negative for these detectors is that they can be knocked loose (even partially) from the receptacle and lose their normal source of power.


7. Warranty

The warranty on a product can be a large part of its value and its price. Obviously, the length of time a product is warranted for is very important, but what is and is not covered by the warranty might even be more important. For battery-powered carbon monoxide detectors, a critical distinction is whether the batteries are covered by the warranty and of course, warranted batteries are worth a lot more than those that are not.


8. Other Considerations

This is a catch-all category that covers any other attributes of a particular detector that warrant notice and discussion. Of particular note here is the matter of calibration. Any instrument-grade carbon monoxide detector requires calibration to maintain its accuracy. The Defender detectors on this site is not of that caliber, but the two small, portable units we feature here recommend calibration annually or more frequently.


9. Price

It is no coincidence that we put this attribute last. As they say, “When it comes to doctors, lawyers, and carbon monoxide detectors, don’t go cheap!” Saving a few bucks is not worth your life, your health, or your family. Get the best carbon monoxide detector that fits your needs. Period.