What if my carbon monoxide detector goes off but then stops?

Author: Kavon Zemlak  |  Last update: Friday, April 24, 2026

If you have a carbon monoxide detector chirping and then it stops, it's important to take the situation seriously, even if the alarm is no longer sounding. Even if the alarm has stopped, get everyone out of the home to a place with fresh air. Contact 911 or your local fire department to report the incident.

What if the carbon monoxide alarm goes off then stops?

If you hear 4 beeps and then a pause, this is an EMERGENCY.

It indicates carbon monoxide has been detected and you should immediately evacuate your home or building and call 9-1-1.

Can a carbon monoxide alarm go off falsely?

While CO detectors are designed to be reliable, various factors can cause them to beep erroneously. False alarms can be caused by incorrect installation, placement near a source of fumes or steam, or even a buildup of dust and dirt on the sensor.

Why does my carbon monoxide detector go off 3 times then stop?

If your detector makes three consecutive beeps around every five minutes, this indicates it is malfunctioning. Newer model detectors will prompt you by saying a recorded message or indicate through light colors. Look to replace your detector.

Why would the carbon monoxide alarm go off randomly?

The carbon monoxide alarm going off could mean the gas is present in your home or office, or simply indicating the battery or alarm needs replacing. The deadly gas is a product of partial combustion of carbon-based compounds where there is not enough oxygen to create carbon dioxide (CO2).

What to Do When Your Carbon Monoxide Detector Goes Off

What if carbon monoxide alarm goes off but no fire?

Your carbon monoxide alarm is going off for one of the following reasons: It is doing its job properly and detects CO pollution in the air. It is a false alarm caused by other household items. The detector is malfunctioning or the batteries need changing.

What are two warning signs of carbon monoxide poisoning?

The most common symptoms of CO poisoning are headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion. CO symptoms are often described as “flu-like.” If you breathe in a lot of CO, it can make you pass out or kill you.

Should I worry if my carbon monoxide alarm goes off?

Do not ignore the alarm. Assume it is working properly and there are unsafe levels of carbon monoxide in your home. 2. All people and pets should quickly evacuate the home and find fresh air.

Can anything else trigger a carbon monoxide detector?

Even with the doors and windows open, any of these activities can trigger carbon monoxide detectors. Using a grill inside the garage or near open doors and windows–Not only is barbecuing among the most common CO-producing activities, but it can also be a fire hazard when done too close to your home.

Does 3 beeps mean carbon monoxide?

Here's a simple guide: Smoke alarms alert you with three beeps in a row. Carbon monoxide alarms alert you with four beeps. A single chirp means the battery is low or the detector should be replaced.

How to tell if carbon monoxide is in the air?

The best way to alert you and your family to unsafe levels of CO is to install a carbon monoxide detector. It works like a smoke alarm, sampling the air in your home and creating a loud alarm when levels of the gas are detected. It's important to evacuate your home immediately when your CO alarm sounds.

How many times will a carbon monoxide detector go off?

If your detector is low on battery, you will likely hear a short chirp every minute. To warn of dangerous CO levels, most detectors will beep 4 or 5 times in a row about every 4 seconds.

What causes carbon monoxide in a house without gas?

Carbon Monoxide sources in the home

CO is produced whenever a material burns. Homes with fuel-burning appliances or attached garages are more likely to have CO problems Common sources of CO in our homes include fuel-burning appliances and devices such as: Clothes dryers. Water heaters.

How to tell if a carbon monoxide alarm is false?

4 beeps and a pause: This means that there is carbon monoxide in the air and you should seek fresh air immediately and call 911. 1 beep every minute: This means that the alarm has low batteries and you should replace them. 3 beeps every minute: This means the alarm has encountered a malfunction and needs replacement.

Does the fire department charge to check for carbon monoxide?

In most areas, the fire department does not charge to respond to carbon monoxide alarms or to check for the presence of CO in a residence. However, policies can vary depending on the jurisdiction or specific fire department. It's always a good idea to contact your local fire department for specifics on their policies.

Will a carbon monoxide alarm go off again if you silence it?

If you “shut it off” it will not be working, so will not detect carbon monoxide. If you reset it, it will activate again if carbon monoxide is detected, as long as the battery/power supply is within normal operating limits. A low battery may cause the alarm to “fail safe” and activate to notify that it needs replacing.

What to do if a carbon monoxide alarm goes off and then stops?

If your CO alarm stopped beeping after being outside in the fresh air for 10 minutes, you may have a possible carbon monoxide leak in your home. We recommend calling your gas supplier or national emergency gas helpline on 0800 111 999 and await further instruction.

Will opening a window help with carbon monoxide?

If you experience symptoms that you think could be from CO poisoning: DO GET FRESH AIR IMMEDIATELY. Open doors and windows, turn off combustion appliances and leave the house.

Why does my carbon monoxide detector go off for no reason?

If your smoke or carbon monoxide alarm becomes contaminated by excessive dirt, dust or grime, and cannot be cleaned, you should replace the detector immediately. You may have placed your smoke and CO alarms in an area prone to false alarms, so relocate the detector if it sounds frequent unwanted alarms.

Why is my carbon monoxide detector beeping continuously then stops?

It is time to replace the batteries in your carbon monoxide detector.

Why do carbon monoxide alarms go off at night?

It is possible to have a carbon monoxide detector going off without any danger present. If you suspect that this is the case, it's important not to ignore it. This could be due to a faulty device, old batteries, or just dust buildup in the unit itself.

Who to call if a CO2 alarm goes off?

CO detectors are very sensitive and designed to alert occupants before CO reaches dangerous levels. If your detectors go off, call 911 and evacuate the home. Be sure to notify them if anyone in the house is experiencing flu-like symptoms.

How to test a carbon monoxide alarm?

How to test your carbon monoxide detectors to ensure they are working properly? To test your carbon monoxide detectors, press and hold the test button on the alarm. The detector will sound 4 beeps, a pause, then 4 beeps for 5-6 seconds. Refer to the user manual for your specific model.

How to clear carbon monoxide from a house?

If no one is feeling symptoms, ventilate the home with fresh air and turn off all potential sources of CO. That includes your oil or gas furnace, gas water heater, gas range and oven, gas dryer, gas or kerosene space heater, and any vehicle or small engine.

How to detect carbon monoxide with iPhone?

Go to the Home app on your iPhone or iPad. , then tap Home Settings. Tap Safety & Security. Tap Sound Recognition, then turn on Smoke & CO Alarm.

Previous article
How to know if a SimpliSafe camera is recording?
Next article
Do old thermostats have a C-wire?