smoke alarm keeps going off every couple of mins why?

[angelf]

Smoke alarm connected to electrics & has battery backup.
Keeps going on & off every couple of mins. When disconnected from electrics it still goes off. Have changed battery but still keeps going off.
Any ideas as to how to sort this problem out?

 

[Softus]

This can sometimes be caused by dust/fluff/spiders inside the smoke detector.

1. Remove smoke alarm and remove battery from it.
2. Put a hoover hose against the air vent on the casing and turn on the hoover.
3. Reinstate the alarm and see if it's fixed.

If not, then replace the whole unit.