Nitrate
Nitrate film base was the first transparent flexible plasticized base commercially available, thanks to celluloid developments by John Carbutt, Hannibal Goodwin, and Eastman Kodak in the 1880s. Eastman was the first to manufacture this for public sale, in 1889. Unfortunately, nitrate also had the drawback that it was extremely flammable (being essentially the same chemically as guncotton) and decomposed after several decades into a no less flammable gas, leaving the film sticky and goo-like (and ultimately dust).
As this happened, the likelihood of auto-ignition increased even further. Projection booth fires were not uncommon in the early decades of cinema if a film managed to be exposed to too much heat while passing through the projector's film gate, and several incidents of this type resulted in audience deaths by flames, smoke, or the resulting stampede. While an accident of this kind was recreated in Cinema Paradiso (1988), the risk was certainly far from fictional; in one instance, at the Laurier Palace Cinema in Montreal on January 9, 1927, a fire broke out during a children's film program and resulted in the deaths of 77 children between the ages of 4 and 18.
The year 1978 was particularly devastating for film archives when both the United States National Archives and Records Administration and George Eastman House had their nitrate film vaults auto-ignite. Eastman House lost the original camera negatives for 329 films, while the National Archives lost 12.6 million feet of newsreel footage. Because cellulose nitrate contains oxygen, nitrate fires can be very difficult to extinguish. The US Navy has produced an instructional movie about the safe handling and usage of nitrate films which includes footage of a full reel of nitrate film burning underwater. The base is so flammable that intentionally igniting the film for test purposes is recommended in quantities no greater than one frame without extensive safety precautions.
Many nitrate films have been transferred in recent decades to safety stock, and original nitrate prints are generally stored separately to prevent a nitrate fire from destroying other non-nitrate films; the gas they give off also affects the emulsion of safety film. Usually nitrate collections are even split up into several different fireproof rooms to minimize damage to an entire collection should a fire occur in one part. It is normal for a theater today to pass rigorous safety standards and precautions before being certified to run nitrate films; this includes a fireproof projection booth, fire chambers surrounding the feed and take-up reels, and several fire extinguishers built into the projector and aimed at the projector's film gate in case a trigger piece of film fabric ignites. Nitrate film is classified as "dangerous goods", which requires licenses for storage and transportation.
Read more about this topic: Film Base