"CD" wrote in message
...
I have a pair of connected EI 151 smoke alarms, must have gone in when
the house went up 10 years ago. They both started doing their low
alarm squeak in the early hours today, there have been no powers cuts
at all. Removing them from the mains & doing a test reveals that the
backup batteries are both flat. I then hear a 3rd low battery squeak
coming from a room where there is no smoke alarm. I trace this to a CO
detector on a cupboard.
Coincidence or cause for concern? The boiler wasn't going & it has no
pilot light, so no gas burning anywhere. All 3 going at once, what are
the chances of that?

Routine maintenance of emergency systems using rechargeable backup batteries
in industrial situations usually involves replacing the batteries every
couple of years.

Colin Bignell