False Alarm: Why Is My Carbon Monoxide Detector Beeping?

A carbon monoxide (CO) detector may have a false alarm if it’s put too close to home appliances or high-moisture areas.
Written by Marlee John
Reviewed by Melanie Reiff
A carbon monoxide (CO) detector false alarm may be caused by a few things including its proximity to fuel-burning appliances, exposure to humidity, or the low quality of the device itself. As the detector works to keep you and your home safe, the slightest environmental changes may cause more worry than peace of mind.
If you’ve ever had your carbon monoxide detector go off, it can be unnerving. While a smoke alarm is often coupled with the smell of burning, carbon monoxide, a colorless and odorless gas, is undetectable yet deadly. 
The Centers for Disease Control and Prevention (CDC) reports that every year, more than “430 people die in the U.S. from accidental CO poisoning”. There are protective measures you can put in place to help protect yourself and your home.
Installing both a carbon monoxide detector and a smoke alarm that are in proper working order is a key part of ensuring safety and maintaining your home. So, what do you do when it goes off?
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What triggers false alarms in carbon monoxide detectors?

Fuel-burning appliances and humidity sources

A carbon monoxide detector is designed to alert when it detects unsafe levels of carbon monoxide in the air. Carbon monoxide is a colorless odorless gas that is often produced as a result of fuels not burning properly
Even in great condition, fuel-burning appliances such as a wood-burning stove, furnace, water heaters, and portable gas heaters may produce small levels of carbon monoxide gas. 
Placing your CO detector too close to these appliances may expose it to increased levels of carbon monoxide and trigger the alarm. Your CO detector should be placed at an adequate distance of 15 to 20 feet away so it does not pick up a false reading. 
Exposure to high moisture and humidity may also affect the functionality of your device. While water in the air likely won’t trigger it, certain parts of the detector may become damaged and increase the possibility of malfunction. 
Do not put CO detectors in bathrooms, steam rooms, or near humidifiers. CO detectors should be kept at least 10 feet away from any humidity sources.
MORE: Does homeowners insurance cover power surges?

Hydrogen gas 

Due to its design, your carbon monoxide detector may be susceptible to interference from other gases—in particular hydrogen. Without getting too much into the nitty-gritty of the science of it, the reason behind this is that hydrogen messes with the chemical reaction that allows your carbon monoxide detector to do its job. 
Lead-acid batteries produce hydrogen which may cause interference with your device and lead to a carbon monoxide detector false alarm. While this is not often the case, it is a notable one depending on the environment of your home or living space.

Internal malfunction 

When your CO detector’s batteries are low, or the machine is in need of replacement, it becomes more unpredictable. A damaged component in your detector will likely cause it to function irregularly and potentially trigger it for no reason. 
This one can be more difficult to fix and may just require you to buy a new device. Carbon monoxide detectors will often have a different alarm pattern to indicate that this is the case. 
Despite the possibility of it being a false alarm, never assume that it is. Unsafe levels of carbon monoxide gas are often the result of appliances in need of inspection, repair, or replacement. Follow the emergency procedure and evacuate immediately to fresh air
Wait for a professional to conduct a safety inspection before reentering your home.
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How to tell if it’s a real emergency 

Always refer to your device’s manual. When your carbon monoxide detector beeps, it’s either doing its job correctly, giving a false alarm, or alerting you that something is in need of replacement. Your device’s manual will inform you of signals specific to your carbon monoxide detector. 
In the meantime, here are some common alert signals and what they mean. 

Four beeps and a pause 

Danger. Your carbon monoxide monitor is beeping because it has detected levels of carbon monoxide in your home. 

One beep every minute 

Low battery. Your carbon monoxide detector is alerting you that the batteries need replacing soon. While this may not be an emergency, get your device's batteries replaced as soon as possible. 
The most dangerous thing, next to carbon monoxide itself, is to be unprotected

Five beeps every minute

Your device is telling you it’s getting old! Everything has a lifespan—even technology. 
Luckily, carbon monoxide devices don’t just die. Instead, they give us some warning before they stop working completely. Invest in a good quality detector that will be able to protect your home—and try to do it before the other one goes. 
Key Takeaway Refer to your carbon monoxide detector’s manual. The false alerts listed above may not (all) be specific to your device.

What to do if your carbon monoxide detector goes off 

Follow these steps:
  • Do not ignore your alarm. Always assume it’s an emergency.  
  • Bring everyone (including pets) to fresh air immediately—outdoors or near an open window. 
  • Call 911 or your emergency services. Be sure to also report if anyone is showing any symptoms of carbon monoxide poisoning
  • Warn any neighbors or a landlord as carbon monoxide can leak through walls.  
  • Do not assume it is safe once the alarm stops. The carbon monoxide detector only signals when to get out, not when to return. Wait for the approval of a professional.
  • Do not reenter your home until the emergency team has identified the source and determined it safe to reenter 
MORE: Does homeowners insurance cover a lightning strike?   

Signs of carbon monoxide poisoning 

While symptoms of low exposure to carbon monoxide can be cleared with fresh air, high and/or prolonged exposure to carbon monoxide can be fatal. The CDC says that
CO poisoning symptoms
may be similar to food poisoning or the flu and may include: 
  • Headache
  • Dizziness or light-headedness 
  • Nausea
  • Vomiting 
  • Chest pain and/or shortness of breath 
  • Fatigue 
  • Confusion 
  • Loss of consciousness 
If you or anyone in your home is showing symptoms of carbon monoxide poisoning, move to fresh air, and call 911 immediately. 

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