David wrote:
Every few days (I think) one or both of the mains smoke alarms cheep once.

On line search suggests that low battery should cause a regular cheep
(already experienced that and changed the battery).

There is also a suggestion that dust could cause a false alarm - but this
isn't an alarm, just a single cheep.

Has anyone else experienced this, and worked out what was causing it?

Combination of low battery and low temperature usually. Typically they
cheep sometime during the night when your just half aware of it. When the
temperature rises during the day they cease cheeping as the battery voltage
rises above the alert threshold.

Then you forget all about it until the next cold night. ;-)

Tim

--
Please don't feed the trolls