I don't think projection booths would have exposed platter reals if films were still made from nitrocellulose.
Those I'll admit I found myself wondering in Cinema Paradiso whether anyone would be so reckless as to leave a large box of loosely-tossed movie film in the projection booth. One stray spark and the whole room would have been in flames in under five seconds.
BTW, I recall reading that the "Heigh Ho" scene from Snow White almost went up in flames when a bigwig disregarded the strict "NO SMOKING" policies of the animation studio. The cells were stacked ready for photographing and only a very quick reaction by a staffer stopped the flames before they hit the characters.