A couple of times it's sounded - yet the display says "0" and - more importantly - the fire has been off. The controls don't seem to work - I had to pull the batteries out.
First time in October I thought it could be low batteries, so I changed them.
It happened again yesterday. Testing the batteries (3xAA) they all read 1.44V. I replaced them with some brand new ones at 1.61V. So far the alarm has been silent. The self test feature says it's OK.
Have trawled through the manual, and can't find anything about this. Is my suspicion this a faulty unit justified ?