What does a blinking blue light on a smoke detector mean?

30 Second Answer

A blinking blue light on a smoke detector means that the sensors have detected elevated CO2 concentrations.

When it comes to our safety, we often rely on technology to help protect us from harm. This is especially true when it comes to fires, which can spread quickly and cause extensive damage.

One way we can be alerted to a fire is through a smoke detector. Most smoke detectors will emit a loud beeping noise when they sense smoke, but some also have a visual indicator in the form of a blinking blue light.

So, what does a blinking blue light on a smoke detector mean?

Essentially, it means that the device has detected elevated levels of carbon monoxide (CO2). CO2 is a colorless, odorless gas that can be produced by burning fuel. It’s also found in car exhaust and other fumes.

At low levels, CO2 is not harmful. However, at high levels, it can be deadly. That’s why it’s important to have a smoke detector with a CO2 sensor if you have any fuel-burning appliances in your home (such as a furnace or stove).

If your smoke detector is flashing blue, it’s important to take action immediately. First, try to determine the source of the CO2. If you can’t find it, evacuate your home and call 911. Once you’re out of the house, do not re-enter until the fire department gives you the all-clear.

It’s also a good idea to have your home inspected for CO2 leaks even if the source is not immediately apparent. A qualified technician will be able to locate the leak and make sure that your home is safe.

So there you have it! If you see a blinking blue light on your smoke detector, don’t ignore it – take action immediately!

Table of Contents

Deeper Look

Every responsible homeowner and apartment dweller knows you need a working smoke detector in your home. But, sometimes, you might see an unusual signal from the smoke detector and wonder what it means. For example, what does the blinking blue light mean on a smoke detector?

Smoke detectors are designed to sense heat or smoke in the room, and their signal light blinks a different color for each type of dangerous condition it may sense. (2)

The smoke detector has several different light colors. The colors mean different things, depending on the alarm’s manufacturer. If you have the manual for your smoke detector, it will explain what each of its alarm colors will mean.

When a smoke detector does not detect a fire but is indicating it is in working order, it shines a solid red or green light (depending on the manufacturer.) When your smoke detector is functioning, there should be a colored light of some type on. (2)

A blinking blue light most often should alert you the smoke detector is registering a high level of carbon monoxide in the room. Carbon monoxide is a very toxic gas for those who inhale it. Carbon monoxide (also called CO2) can cause serious health problems within a few minutes and has no smell. So, it is good that smoke detectors let us know when it is present. (2)

The blue blinking light can also be present if the alarm is still in use from a previous alarm. When the alarm senses there is no longer a fire present, the alarm may continue to blink blue to indicate there was a fire. (2)

If your blue light blinks, you should open your windows and your door. When you let clean air into your home, it will decrease the amount of carbon monoxide. After that, call 911 immediately, and leave home for your safety.(1)

Once emergency personnel have confirmed that CO2 or fire situation is resolved, you can go to the smoke alarm and press the “test” or “silence” button. Press this button for 4-5 seconds. This should reset the alarm and shut off the blue light. (1)

After an alarm, you should consider changing your smoke alarm battery to be sure it is operating correctly. (You should also change your alarm batteries twice each year on dates you will remember – like December and June 1.) (1)

If you have reset the alarm and replaced the batteries, but the light is still blinking, you should replace the entire alarm apparatus. (1)

Your smoke alarm is a safety must. Its lights are intended to give you a message related to your safety. If your smoke alarm blinks blue, it usually means it has detected a high level of carbon monoxide in your home. Co2 is a toxic gas, and you need to correct the condition. Call 911 and leave the home. A blinking blue light might also mean there was a previous fire, and the device is still blinking from that fire. You can reset the alarm after you are sure the source of danger is gone.


If you see a blinking blue light on your smoke detector, don’t ignore it – take action immediately! A qualified technician will be able to locate the leak and make sure that your home is safe.

(1) “What Should I Do If My Carbon Monoxide Detector Goes Off?” posted on carrier.com



(2) “Why Is My Smoke Detector Blinking Blue? (Read This First!)” posted on homeapricot.com