In message , john east
writes
Have an ordinary house smoke alarm. It's about twenty years old and it has
recently gone off in the middle of the night for two days running and for no
apparent reason.

I've heard that it might need a vacuum cleaner applied to it. Is there
likely any truth in that, or is there anything else i might usefully do?

Or does it probably mean that I have to replace it?

Is it battery or mains powered?
Batteries go slightly higher resistance when cold. If I don't keep an
eye on the battery indicator my pager goes off in the early hours when
its battery is nearly flat, I put this down to the cold.

If battery then try changing it and see if it still does it.


--
Bill