Your home can slowly be filled with carbon monoxide without much warning. There is no color, odor or taste to carbon monoxide, making it very difficult to find and giving it the nickname of "silent killer." This is where carbon monoxide detectors come in.
When humans breathe in carbon monoxide, it binds to the hemoglobin in their red blood cells, replacing and reducing the amount of oxygen that can be carried by the blood. This leads to a range of symptoms, from headaches and dizziness to confusion, nausea and even death.
Having a carbon monoxide detector in your home will help protect your household from this potentially deadly gas. The detector can alert you to the presence of dangerous levels of carbon monoxide and give you time to evacuate and, if necessary, seek medical attention.
To help you make the right decision, we gathered seven of the most popular carbon monoxide detectors, including some that double as smoke detectors, and evaluated their ability to detect carbon monoxide at two hazardous concentration levels: 250 and 400 parts per million. Here are our picks.
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.
Gianmarco Chumbe/CNETThis 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.
Gianmarco Chumbe/CNETThe 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.
Gianmarco Chumbe/CNETWe 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.
Show more