Should a carbon monoxide detector flash?

Author: Westley Nitzsche  |  Last update: Wednesday, February 4, 2026

On First Alert® carbon monoxide alarms, the red light flashes to show the Carbon Monoxide Alarm is properly receiving battery power. If you do not see the red light flashing, change the batteries in the alarm immediately.

Why did my carbon monoxide detector flash?

A blinking red light on a smoke and CO2 alarm can mean a few different things. It could mean that the batteries are low, that the unit needs to be replaced, or that there is smoke or carbon monoxide present. If the green light is still on, it's likely that the unit is still working properly.

How do you know if carbon monoxide alarm is working?

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.

Is my carbon monoxide detector supposed to blink?

Why does the red light flash on my carbon monoxide alarm? Do I have CO? On First Alert carbon monoxide alarms, the red light flashes to show the CO alarm is properly receiving battery power. If you do not see the red light flashing, change the batteries in the alarm immediately.

How to tell if carbon monoxide is leaking?

What Are Signs of Carbon Monoxide in Your Home?
  1. Yellow or orange flames coming out of your gas appliances instead of the usual blue flame.
  2. Dark and sooty staining on or around gas appliances.
  3. Pilot lights that frequently blow out.
  4. Increased condensation on windows.
  5. Solid fuel fires burn much slower than usual.

Understanding Smoke and Carbon Monoxide Detectors | Ask This Old House

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.

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.

What if the carbon monoxide alarm goes off but no fire?

False or nuisance alarms are when your smoke detector or CO alarm goes off, but there is no presence of smoke or carbon monoxide in your home. However, if your smoke or carbon monoxide detector sounds indicating an emergency and you are not certain it is a nuisance alarm, evacuate the home and call 9-1-1.

What color does a carbon monoxide alarm flash?

- Red light flashes 8 times (in 2 seconds) every 40 seconds, 300 ppm CO detected for at least about 3 minutes. When the test button is pressed the horn will sound, and the red light will only flash if the unit has previously detected CO and been in alarm.

What else can trigger a carbon monoxide detector?

Any fuel-burning appliance that is malfunctioning or improperly installed. Furnaces, gas ranges or stoves, gas clothes dryers, water heaters, portable fuel-burning space heaters, fireplaces, generators, and wood burning stoves. Vehicles, generators, and other combustion engines running in an attached garage.

How many times should a carbon monoxide detector beep?

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.

Why is my carbon monoxide detector blinking red every 30 seconds?

Carbon Monoxide Detector Replacement FAQs

When the CO alarm emits a quick beep every 30 seconds and the red LED flashes, the unit has reached the end of its 7 or 10 year life.

Should my carbon monoxide detector be flashing green?

The sounder will sound as soon as the button is pressed, and the Alarm LED will illuminate red indicating that the sounder is working, and the power pack is providing power to the unit. Please note – it can take up to 1 minute for the green LED to flash to confirm your alarm is active.

How do I know if my carbon monoxide detector needs a new battery?

When the CO alarm emits a quick beep every 30 seconds and the red LED flashes, you may need to change the batteries. Replace the batteries in the alarm. If the alarm continues to emit a quick beep every 30 seconds and the red LED flashes, the alarm has reached the end-of-life.

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

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.

How to test a carbon monoxide alarm?

How to test a carbon monoxide detector:
  1. Hold the “test” button until you hear two beeps sound off.
  2. Once you hear these beeps, release your finger off the test button.
  3. Repeat this process but hold the test button until you hear four beeps.

Can I call the fire department to check for carbon monoxide?

Yes, the fire department can check for carbon monoxide. If you suspect the presence of carbon monoxide in your home or building, it's essential to act quickly. Evacuate the area, ensure everyone's safety, and call your local emergency services or fire department.

What do 4 beeps on a carbon monoxide detector mean?

4 Beeps and a Pause: EMERGENCY. This means that carbon monoxide has been detected in the area, you should move to fresh air and call 9-1-1. 1 Beep Every Minute: Low Battery. It is time to replace the batteries in your carbon monoxide detector. 5 Beeps Every Minute: End of Life.

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.

Why is my smoke detector blinking red every 30 seconds?

A red blinking light can indicate several things depending on the model and make of your smoke detector. Typically, a red light that flashes every 30 to 60 seconds is a standard feature indicating that the smoke detector is functioning correctly and is actively monitoring for smoke.

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.

How do I use my iPhone to detect carbon monoxide?

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.

What's the most common household thing to cause a carbon monoxide leak?

How can carbon monoxide build up in a home? The most common causes of carbon monoxide building up are incorrectly installed or poorly maintained or ventilated appliances – like stoves and hot water heaters. Poorly ventilated fireplaces and other gas- or wood-burning appliances can also pose danger.

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