A mains powered fire alarms can be beeping for a number of reasons.
Beeping or chirping is normally due to low backup battery power in the unit. Beeping most commonly starts at night as the temperature decrease causes a decrease in battery power.
If the unit has a replaceable battery, replacing this usually resolves the problem. Check your user manual to ensure you use the correct type of battery and go for a good quality battery rather than a cheap alternative.
If the unit has a sealed battery or the beeping continues after changing the battery, check the manufacturing date of the alarm. Alarms aren’t unfortunately designed to last forever and do need replacing. The beeping could be a warning that the electronics inside are becoming faulty or that the lithium battery is at the end of its life.
Another cause for a beeping fire alarm could be that there is a problem with the electrical supply. You’d need to get an electrician to have a look at this for you.
Alarm sounding when there isn’t a fire or smoke
We’ve probably all been there wafting a towel near the alarm when making a bacon sandwich has caused the alarm to go off, but sometimes an alarm goes off without reason.
The most common reason for false alarms is contamination (such as dust and small insects) within the sensor chamber. Sometimes, cleaning the unit by vacuuming around the detection chamber or blowing the contamination out with a hair dryer on cold can resolve the problem, but if this doesn’t help you’ll probably need to replace the alarm.
Note: Your fire alarm may have been designed to enable you to change it without having to get an electrician to do that. You should be able to find this information in your user manual.