Person testing alarm

Smoke Alarm (Smoke Detector) Troubleshooting

A working smoke alarm in your home can alert you to a fire, giving you time to safely get out of the house. Knowing the different sounds, a smoke alarm makes is key to understanding what to do.  If your smoke alarms sound, you should exit the house as soon as possible and follow your home fire escape plan. However, if you keep having nuisance (unwanted) smoke alarms when there is no fire, here are a few things that can help you determine the issue.  

I also want to note that there is a difference between a smoke detector and a smoke alarm, basically a smoke detector is just a sensor that monitors for smoke and is connected to a whole building fire alarm system, while a smoke alarm has both the sensor to monitor for smoke and a speaker that emits the sound to notify the occupants in the home.  For this discussion I am referencing home smoke alarms.

Here is a quick guide to use if you are trying to figure out the sounds coming from your smoke or carbon monoxide alarms. I will explain all of these in more detail below.


One alarm can cause all of them to go off

Some smoke alarms can be interconnected so that when one detects smoke, all of them go off. This is important because a fire in another portion of your home can be causing all your smoke alarms to be going off to alert everyone in the home. A single faulty smoke alarm can also cause all your smoke alarms to go off when there is no fire.

If all the alarms are going off without a fire, you need to identify which smoke alarm is the one that is initiating the alarm.  You can determine this by checking the instructions printed on the back of one of the alarms to see how the specific model of smoke alarm identifies the initiating alarm. Typically, this is indicated with a led light indicator on the initiating smoke alarm. You may also be able to hit the silence button on any smoke alarm, which will cause all the non-initiating smoke alarms to silence so you can hear just the initiating one.  Once you have determined which one is initiating the alarm and there is not a fire, there may be a few reasons for this alarm sounding.

It could be a carbon monoxide (CO) alarm

You can’t see or smell carbon monoxide (CO), but it is still very deadly. In your home carbon monoxide may be released by a malfunctioning gas or oil-fed appliances (stove, water heater, furnace), a fireplace, or even a car running in the garage. Whether you have a combination smoke/CO alarm or separate CO alarm, if the sound you are hearing is a temporal 4 pattern (see video below), meaning there are 4 beeps followed by a pause repeatedly, the alarm you are hearing is for carbon monoxide. Exit your home immediately and call 911 so the fire department can come investigate the issue. A combination smoke alarm/ CO alarm will look the same as a smoke alarm (see image below).


The alarm could be dirty

If you have determined that the alarm is a smoke alarm, meaning it is a temporal 3 (three beeps and a pause) (see video below) and not a CO temporal 4 (4 beeps and a pause), then it is possible that the smoke alarm is dirty.  Dust, dirt, and even spiders can get into an alarm and make it falsely sound. They can be cleaned with a vacuum or compressed air. Look at the back of the alarm to see if the manufacturer specifies one cleaning method over the other and to see the recommended frequency. The image below shows that this manufacturer recommends vacuuming the alarm monthly.  


Steam can be the problem

If your smoke alarm is mounted near a bathroom, it is possible that steam from the shower has set off the alarm. Alarms should be placed at least 36 in. (910 mm) from the bathroom door to eliminate the nuisance alarms from steam. Areas of high humidity or spaces with a humidifier can also cause issues with the alarm. If the smoke alarm is installed near a cooking appliance (stove, oven, etc.) it could falsely alarm, so consider moving the alarm further from the appliance.

How is the temperature?

Smoke alarms are designed to be used in a specific temperature range, typically 40F to 120F (4C to 49C). If the temperature has risen above or fallen below those temperatures (such as freezing in a garage) it is possible for there to be a false alarm. Check the manufacturer’s instructions for the required temperature range.

If your alarm is chirping

If the sound you hear is a “chirping” sound or a very short beep (see video below) then the alarm is notifying you that there is an issue with the alarm. Look at the back of the alarm for the description of the different types of sounds and what they mean as each alarm is different (example shown below), but in general a single repeated chirp can mean one of the following:

  • The battery is dying. If the alarm has replaceable batteries, replace them. If it is a sealed unit with a 10-year battery, replace the alarm.

  • End of Life means that if the alarm is nearing or past 10 years from the date of manufacturer, it will need to be replaced.If the alarm is less than 10 years old and new batteries still result in chirping, replace the alarm anyway.



Continued Issues

If you are still having issues with your smoke alarm that you cannot figure out, look on the back of the alarm for information on how to contact the manufacturer for troubleshooting. Additionally, if you would like someone to come out and inspect the alarm(s), most municipal fire departments or local fire marshals are willing to come out and look. Just give the fire department a call on their non-emergency line or call the fire prevention department.

Learn more

To learn more about the different types of smoke alarms and how to choose the best alarm, read my blog on purchasing smoke alarms, or check out our Fire Prevention Week Website, Public Education Smoke Alarm Page, Carbon Monoxide Alarm Page, or Chapter 29 of NFPA 72®, National Fire Alarm and Signaling Code®.

Important Notice: Any personal opinion expressed in this blog is the opinion of the author and does not necessarily represent the official position of NFPA or its Technical Committees. In addition, this piece is neither intended, nor should it be relied upon, to provide professional consultation or services.

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Shawn Mahoney
Technical Services Engineer with a masters degree and PE in fire protection supporting subjects throughout the association

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