Top Carbon Monoxide Detector for Emergencies (updated for 2024)

Carbon Monoxide Detector, Low Level CO Detector -

Top Carbon Monoxide Detector for Emergencies (updated for 2024)


In the United States, around 50,000 people visit the emergency room each year because of carbon mon­­­­oxide (CO) poisoning. An informal investigation by Chicago’s CBS Channel 2 suggests expired CO alarms are a key factor in hospitalizations. 7 out of 9 units gathered from volunteers failed when exposed to lethal amounts of carbon monoxide; all were over 5 years old. In a larger study published by the American Journal of Public Health, 12 out of 30 alarm detect­ors collected from volunteers failed; all but 2 were over 5 years old. In both studies, several homes had been relying on CO alarms that were over 14 years old.


  • Improved Awareness: Increased understanding of the risks of carbon monoxide (CO) poisoning and the importance of having functional CO alarms.
  • Technological Advancements: Availability of CO detectors with advanced features such as digital displays and longer lifespans.
  • Specialized Options: Existence of alarms specifically designed for high-risk individuals, capable of detecting low-level CO exposure.
  • Awareness of UL 2034 Limitations: Knowledge that UL 2034 compliant alarms may not activate at lower, yet hazardous, CO levels.
  • Portable and Travel-Friendly Options: Availability of portable, battery-operated CO detectors for additional safety in different settings.


  • False Sense of Security: Potential over-reliance on CO alarms without understanding their limitations, particularly for low-level CO exposure.
  • Sensor Degradation: CO alarms have limited lifespans, often deteriorating after 5-7 years, which can lead to failures.
  • Testing Challenges: Standard testing methods may not effectively assess the electrochemical sensor critical for detecting CO.
  • Risk of Malfunction: Alarm accuracy can be affected by environmental factors like temperature and humidity, leading to false alarms or failures.
  • Restricted Display: UL 2034 alarms are designed not to show CO levels under 30 ppm, possibly delaying necessary response actions.

Carbon Monoxide Alarms in the Home

Like other electronic gadgets, carbon monoxide (CO) alarms can also malfunction. These alarms generally have a shorter lifespan compared to other devices, such as smoke detectors. In most home CO alarms, the electrochemical sensors deteriorate over a period of 5 to 7 years. However, some brands now offer alarms with a claimed lifespan of 10 years, achievable under optimal conditions of temperature and humidity.

Despite manufacturers recommending monthly or weekly tests of these alarms, many go untested. More critically, the common "push to test" function only verifies the battery, electronic circuit, and alarm sound, but does not test the electrochemical sensor. Below, I will detail a method to test this sensor, but it's essential first to grasp how the alarm operates.

CO Concentration (ppm)

UL 2034 Alarm                       Response Time


0 - 29 ppm


@9 ppm – Possible health risks with long-term exposure.

30 - 69 ppm

30 days

@30 ppm – Hazardous for those with a heart or respiratory illness, infants, elderly, and pregnant mothers.

70 - 149 ppm

60 - 240 minutes

@100 ppm – Headache and dizziness after 1 - 2 hours.

150 - 399 ppm

10 - 50 minutes

@200 ppm – Headache, dizziness, nausea, fatigue after 2 - 3 hours, followed by unconsciousness and eventual death.

> 400 ppm

4 - 15 minutes

@400 ppm – Life threatening in 3 hours.

@800 ppm – Unconsciousness after 1 hour, death within 2-3 hours.

@3200 ppm – Unconsciousness after 30 minutes, death in 1 hour.

@6400 ppm – Death within 30 minutes.


Organizations focused on the long-term effects of low-level CO exposure have established more rigid standards to minimize its impact on brain chemistry and protect high-risk individuals. For instance, the World Health Organization (WHO) is one of many agencies that recommends no more than 35 ppm exposure for 1 hour. In contrast, you’ll note from the chart above that UL 2034-compliant alarms will not sound until you’ve been exposed to that concentration for 30 days. At 8 hours of exposure, WHO recommends no more than 9 ppm, a level that would NEVER trigger your UL 2034 alarm.


Accordingly, user guides for UL 2034 alarms warn: “This device … may not fully safeguard individuals with specific medical conditions. Also, young children and household pets may be the first affected. You should take extra precautions to protect high-risk persons from CO exposure…. Consider using warning devices which provide audible and visual signals for carbon monoxide concentrations under 30 PPM.”

Digital Display

In other words, you’ll need a non-UL 2034, low-level CO monitor to display and alert at these levels. The stan­dard prohibits displaying carbon monoxide levels under 30 ppm to reduce emer­gency calls. UL 2034 alarms equipped with a digital display provide of a way of observing levels above 30 ppm, although they won’t sound the alarm for 30 days.

We highly recom­mend a portable, low-level, battery-operated detector with a digital display in addition to your home’s hard-wired sys­tem for a few different reasons. First, you can use it as a supplemental monitor in a room with a stove or in the bedroom of a high risk fam­ily member, such as a child. Sec­ond, you can use it while traveling to monitor CO levels in hotel rooms, campers/RVs, or house­boats. And third, in the event of a power outage, you can place it 7 - 8 feet away from your port­able emergency stove to detect escalating CO levels well before any UL 2034 alarm would trigger.      


Residential CO sensors don’t provide the accuracy of premium, calibration-enabled sensors used in industrial monitors that cost hundreds of dollars. However, these devices generally function within a tolerable margin of error so long as the sensor remains viable and unfouled. Temperature and humidity have the largest impact on accuracy. A steam­ing hot shower could set off the alarm by causing a CO over-read, while low temp­eratures can result in an under-read. This is particularly import­ant to our application. Since you’ll likely be cooking in a cold room during a winter power outage, actual CO levels could be much higher than what the sensor is able to detect. Below 40°F, the detector essentially becomes non-functional.

Testing the Electrochemical Sensor

Now that you understand the restrictions imposed by UL 2034 and the impact of the surrounding environment on accur­acy, you can test your alarm sensor with a few matches, a small glass or metal cup, and a gallon-size Ziplock bag. Place the glass on its side within the Ziplock bag along with the CO detector. Light three matches, let them burn about ½ an inch, then place them together in the cup and quickly seal the bag. Within about two minutes, the device should record a measurement of around 400 ppm, activating the 4 - 15 minute alarm response window specified by UL 2034.

carbon monoxide

In my case, the unit failed “safe” as it alarmed about 37 sec­onds before another 4 minutes had elapsed. That’s of course preferable to failing “unsafe,” alarming after another 15 minutes. If the device is in active use, test the sen­sor twice a year, such as when you change your clocks each spring and fall. If used only for emergen­cies, test it before putting it to use.

carbon monoxide

Sensor Fouling

To avoid fouling the electrochemical sensor, avoid exposure to high levels of chemical contamination. For instance, don’t allow auto exhaust, air fresheners, paint, or aerosols near the alarm. In addition, move the device to a remote location before chemically treating floors or furniture, painting, or changing refrigerant. Note that such chemicals can also cause temporary readings that are not carbon monoxide as most residential CO alarms are subject to cross-sensitivity.

Top UL 2034 Budget Pick

Our favorite budget pick is the Kidde 10-Year Sealed Lithium Battery Power CO Alarm with Digital Display C3010D. For around $35, this UL 2034-listed device displays CO levels above 30 ppm within a 30% margin of error and is suitable for most healthy adults. It is a highly-rated de­tector with a 10-year life span and a 10-year limited warranty. As missing or dead batteries is the leading cause of alarm failure, we always opt for long-life, sealed lithium batteries when available. Runner-up in this category goes to the $33 First Alert CO710.

Top Pick for High Risk Individuals

If you need to protect older adults, pregnant women, young child­ren, or those with medical condi­tions, we recommend the Fast & Low CO Mon­itor from Foren­sics Detectors. For around $65, it dis­plays CO levels as low as 10 ppm, compliant with the most rigid domestic and interna­tional air qual­ity standards. The device trig­gers an audible alarm at 25 ppm after 1 minute and has the fastest refresh rates and response times of any comp­et­itor in its class. Runner-up in this category goes to the $60 Kidde KN-COU-B, a non-UL 2034 version of the previously mentioned C3010D programmed to display CO levels below 30 ppm.


Summary of CO Detector Performance.

To capture the above results, we placed all three units in a glass pan with three extinguished matches and covered them with plastic wrap. The Forensics Detectors device took just over 30 seconds to begin reporting CO levels, followed by an alarm at 60 seconds.

The Kidde KN-COU-B began reporting at 74 seconds. In addition to displaying low levels of CO, this “ultra-sensitive” device has a faster refresh rate than its C3010D predecessor, but slower than Forensics Detectors.


The Kidde C3010D began reporting at 105 seconds. We included this unit in these tests sim­ply for informational pur­pos­es. As mentioned, UL 2034 devices are not in­tended for high-risk individuals. It took over 18 minutes to alarm at the dangerous level of 300 ppm, while lower levels take hours or even days.

The Kidde KN-COU-B finally alarmed at 9 minutes, a full 8 minutes after the Forensics Detectors 1-minute alarm. At lower concentrations, this alarm can take over 8 hours to sound and will not go off for levels below 40 ppm. In our opinion, this device is  better suited for observation than alerting.


Forensics Detectors was established in 2017 out of concern for the lack of affordable and effective toxic gas alerting products. It was founded by PhD engineer, Dr. Koz, who became aware of this need after US law firms began engaging him as a world-renowned expert consultant. Inventor of the world’s first ve­hicle car­bon mon­o­­xide sensor system, his award-winning analyzers have outperformed some of the world’s best sen­sors. His informative site contains links to his youtube channel and other innova­tive pro­ducts, such as a compact model that was awarded “Best Travel CO Detector” by

I’m grateful to Dr. Koz for spending a generous amount of time with me responding to my many ques­tions on this topic and for providing a final edit of this article. After learning about the intent of our research, he suggested that we also inform you of the elevated risk of CO exposure following natural disasters due to the potential for damaged flues, caps, furnaces, shields, heat exchangers, etc. He graciously offered to publish this writing on his website.

Final Words

  • Slightly lighter than air, this odorless killer is invisible to all human senses of perception. As such, the importance of effective carbon monoxide detection can­not be over-stated, just as an under­stand­ing of detector limita­tions can­not be over-emphasized. 
  • Be cognizant of the flu-like symptoms associated with CO exposure. It is also important to understand the ra­tion­ale behind UL 2034, so you can make complimentary provis­ions to safe­guard your family mem­­bers now while simultaneously preparing for future emergencies. We’ve chosen to augment our whole-house alarm system with low-level CO alarms at 5’ on each level of the home and will ensure that our missionary children take one with them into the field.
  • Any combustion appliance, such as a water heater or furnace, is a persistent threat but portable stoves pose an even higher risk. If use of a stove in­doors is ever considered due to a pro­long­ed power out­age, a portable, low-level CO alarm is an indispensable asset that should be kept within 7 - 8 feet away.
  • That said, NEVER allow reliance on a CO detect­or as just­ifica­tion for skipping rule #1. Ven­tilation, esp­ecially in the middle of winter, is the single-most im­por­tant ac­tion you can take to manage the effects of in­com­plete combus­tion, therefore re­duc­ing the like­lihood of car­bon monoxide exposure.

Week 14 of a series of articles on Emergency Cooking Preparedness, 2021-04-20
by Robbie & Gina Jackson