Robert Bradspies wrote, "Old decomposed nitrate should be considered a HIGH
EXPLOSIVE."
This is true only of movie film and that's because it is stored rolled in a
metal cannister.  I ran across some severely deteriorated nitrate movie
film years ago in the collection of an arboretum's archives.   The local
police and fire people  wanted no part of it, but the bomb squad for a
state agency were thrilled and had a new experience exploding the stuff.  I
have never heard of cellulose nitrate film exploding if it's in sheet
format.  It would require a combination of extraordinary housing and
environmental conditions for sheet film to combust simultaneously.   I am
not suggesting that nitrate negs in still photo collections don't require
special attention-- they do.
For further information, an excellent reference is "Archives & Manuscripts:
Administration of Photographic Collections" by Ritzenthaler, Munoff and
Long.  It's part of the SAA Basic Manual Series, and I think it's the best
of its kind.

Michael McColgin                               Phone: (602) 542- 4159
Preservation Officer                            Fax: (602) 542- 4402
Arizona State Archives                      Email: [log in to unmask]
1700 West Washington                      Smoke Signal: 0 oo 000 o0o0
Phoenix, AZ  85007

                   Conservators make it last longer.