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 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.”
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.
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.
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 Health.com.
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.
- 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.