A cheeping or beeping smoke alarm can be an annoying and sometimes familiar sound for anyone who lives in a property that is fitted with alarms that carry a 9-volt battery. So why does a smoke alarm beep constantly?
More often then not a cheeping alarm indicates a problem with power supply. This could be true for both mains powered alarms and battery or lithium only powered alarms.
9V Battery fault:
Mains power alarms carry a 9-volt battery as a power source back up. So, if there is a black out you still have an operating fire warning system.
Whether your smoke alarms are mains powered, lithium powered, or battery powered you need to know when the battery is flat, so manufacturers have built in a sound function to let you know… hence the cheeping or beeping.
When you think there is a flat battery you should simply replace it with a new one and this will stop the “cheep”.
Lithium Battery fault:
Alarms that are powered only by a 10-year lithium battery are a little bit different. You cannot just change the built in 10-year lithium battery.
When there is a fault with an alarm that has a built-in lithium power source you need to replace the whole alarm with a new one.
Some alarm models also have sound functions built in that indicate issues with the alarm other than inconsistent power supply.
You will need to check the user manual for your particular model. Some models have particular beep sequences to indicate whether an alarm has been triggered recently, whether an alarm is resetting or even possible faults within the alarm itself.
When to Replace the Alarm due to cheeping:
If cheeping noises continue for more than one hour after replacing any 9V battery or testing the alarm using the test button, then it is probably faulty and should be replaced.