Close Encounters of the Third Kind?

Testing the old smoke machine on Sat ready for a concert on the 4th.

I hadn't fired this up for a good few years.

It filled the church with smoke in about 5 minutes (and triggered most of the smoke detectors in the building!)

It then took the extractor fans 2.5hrs to clear the building before we could reset the alarms....

(Don't worry - we had disabled the alarm bells and the auto dial to the Fire Brigade)