I've come across an issue at a site where its been fine for over a year and now im getting spurious alarm signals between 12am and 3 am from various long rang detectors. It started with just one detector so it was changed but now its multiple including the changed one.
Its a large builders merchant with a large warehouse, there isn't any sign of animal life. The only thing is the warehouse is rather hot and I wondered whether the cooling of the building would effect these particular detectors. The thing is now isn't as hot as it was so i'm a little stumped.