Not unusal, but I started a chain of events that caused a fire:
I inspected an industrial site - multi unit, small businesses (fencing, builders storage etc). There was no file for the site, just one for an isolated building that had a fire cert. The whole site was a tip, with cylinders lying around, burning of industrial waste, open chemical barrels etc. I got the number of the owner, who had just wrestled control away from his business partner, and after years of neglect, wanted to get it in order, so was keen for me to give him advice.
One if my main concerns was the lack of fire separation between units, and told the guy that a fire in one unit could very easily spread into other units, and as the site was next to a railway line, told him of possible fines for causing delays to trains. So he agreed that it would be a good idea to put FR between units. The guy he got to do this was welding some fixings to the structure to put the boards, and sparks went down into a clothing recycling unit below, set it on fire, and wiped out four units, and delayed trains for several hours.