As most people know, before the invention of "safety" film, movie film
stock was also made of this.  With those old carbon arc projectors,
risk of fire in the projection booth was a serious concern.  Theatres
had heavy fire doors suspended over all of the windows through which
the movies were shown, with fusible connectors that would quickly melt
if there were a fire, dropping those doors and effectively sealing off
the projection booth from the theatre.

Interestingly enough, the brightly colored stop tabs on theatre organs
were also made of nitrocellulose, providing considerable danger if
there were sparks in the console (or a smoking organist!).

David C. Kelzenberg
Iowa City, Iowa