Din Zone Monitor

Hi all

enjoying nice sunny day :-\

I got call out to fire alarm, found zone monitor activating, checked MCPs all ok, smokes...fine. Measured zone wiring and all ok.. I've not come across any of the Din type before.. Found a spare in the same enclosure, swapped and still activating.. (bit suspect another in same enclosure, possibly faulty etc) so... Question is do these things have tendency to trigger themselves?

forgive my absence, I like super long hoildays, unfortunately of course I've been working my ass off, of course ;)

Pedro