Why is my smoke alarm beeping?

There are a number of possible reasons why a smoke alarm could be beeping. The most important thing is to not ignore this, as they are warning signs of either a danger in the home or that an alarm needs maintenance.

The smoke alarm is equipped with a sounder and LED’s in order to communicate with you. The sounder is used when the communication is important (or imminently dangerous).

The two main reasons that smoke alarms chirp or beep is to alert the occupants of a low power condition or to alert of a contaminated detection chamber. To distinguish between the two, please take the following steps;

Battery Powered Mains Powered
10-year non removable lithium battery

If the alarm is beeping about once a minute with the red light flashing at the same time, indicates that the lithium battery is partially depleted and the alarm needs to be replaced (check the “replace by” date marked on the side of the alarm).

10-year lithium rechargeable, non-replaceable back-up battery

Look at the smoke alarm and ensure that the green LED is illuminated. You may see the red LED flash every 40 seconds, this is perfectly normal and indicates that a “self-test” cycle has been conducted. If the green LED is not illuminated, then there has been a mains power failure and the smoke alarm back-up battery is nearing depletion. Please check and reset the circuit breaker in your home’s distribution board and return to examine the status of the indicators. If in doubt contact a licensed electrician.

If the alarm has been chirping/beeping as a result of mains power failure and the battery is nearing charge depletion, the alarm may continue to chirp/beep for a few hours while the rechargeable battery is being recharged after mains power restoration. This will stop as soon as the battery charge point exceeds the lower threshold.

9-volt replaceable models only

A fresh Alkaline battery should last for over a year. When the battery power is low and replacement is necessary, the smoke alarm will beep and the red light will flash at the same time about once per minute for at least 30 days. The heat alarm will also beep once per minute, but the red light will not flash at the same time when the battery is low. The battery must then be replaced. Also, replace the battery if the alarm does not sound when the Test button is pressed. For maximum reliability, replace the battery at least once per year. When you replace the battery, you must press the test button to check that the alarm is functioning correctly.

9-volt alkaline battery back-up

If you have a mains primary powered smoke alarm with a replaceable 9-volt Alkaline battery and the alarm beeping/chirping coincides with the red LED indicator flashing (once every 40 seconds), then this is an indication that the back-up battery is in need of replacement. Please replace the depleted battery with one of the following brand types;

•    Duracell MN1604,
•    Energizer 6LR61,
•    Philips 6LR61,
•    Varta 6LR61 or
•    Ultralife U9VL-J Lithium


If the chirping/beeping is not being indicated as a loss of mains power or a depleted back-up battery, then it is likely that the smoke alarm may be contaminated with dust. Remove the alarm head from the base and use a vacuum cleaner with a nozzle fitted or a compressed air source to dislodge any loose dust from the chamber. Re-install to determine if the chirping or beeping has stopped.


For Brooks alarms that are AudioLINK™ enabled, downloading our free “App” onto your smart phone (Apple or Android) will provide an additional method to determine the cause of the beeping alert on your alarm. Look for the data in “red-boxes” on the resultant test report. Please follow the AudioLINK™ instructions contained within the App on how to use this feature.

To find out if your alarm is AudioLINK™ enabled, look for the small “smartphone” icon on the front of your alarm.