Have Aico Ei141 - 2 smoke alarms mains connected with back up batteries. One downstairs in hall and one upstairs in hall. One downstairs was beeping so assumed needed new battery. Eventually put in new battery but had trouble removing the base of the alarm to refit new battery. Put back on and reconnected to the mains supply - we have a special switch for smoke alarms on our fuse box. Every time put on mains alarm upstairs goes off very loudly, indicating a fire. I have tried cleaning and hoovering dust from both units, but does not work. Any ideas. I have ordered a replacement base for our downstairs alarm in case faulty.

Hi Susan,

Do you know how old the units are?

There are a number of reasons why a smoke alarm will false alarm:

1. The batteries are faulty (may be prudent to try new batteries in the upstairs unit)

2. A build up of dust/insects in the sensor chamber (I know you have hoovered dust from the units, you can also try a hair dryer on cold to blow anything out of the chamber)

3. There could be a problem with the mains supply getting to the unit (the damaged base unit on the downstairs alarm could be contributing to this or it may be an unrelated and coincidental issue)

4. The alarms are over 10yrs old and the sensor has degraded to a point where it is giving a constant false alarm and the unit needs replacing.

If none of this helps and the replacement base has no effect you can call Aico direct on 0870 758 4001. Their technical dept. is very helpful and knowledgeable.

I would say change them both, sounds like one has been damaged.