Not really unless they have been stored in exceptionally bad conditions; some prints or negatives MIGHT be plagued by this, but I never saw that problem more than once or twice in my 13 years of handling Nitrate at the LOC and we had 130 million feet of the stuff...
Originally Posted by Photo Engineer
Now, ferrotyping and silvering are pretty common, as are spoke set and other physical problems, but those come from out gassing of the base for the most part.
The original negative to "the Great Train Robbery" (1903) by Thomas Edison, D by E.S. Porter, is still easily run through a modern contact printer to make new prints from it.
The film stock itself is not explosive, it is inflammable, burns rapidly and gives off hydrogen, oxegen, nitric acid and phosgene (to name a few gases), but the explosive nature comes only when ignited in a confined space where the gas can accumulate in an oxegen poor environment.
Once the film burns enough to liberate enough oxegen to cause "over flash" it explodes.
Please note that the base will burn under water; you cannot put it out once it starts burning...
There have been reports of spontaneous combustion at temperatures as low as 120 F in tightly sealed containers, but the film does not "sweat nitroglycerin" as I have heard rumored.