JOURNAL OF SMPTE Volume 54
Spontaneous Ignition of Decomposing
Cellulose Nitrate Film
BY JAMES W.
ARCHIVES AND RECORD SERVICE, WASHINGTON, D.C.
C. HUTTON AND HOWARD SILFIN
BUREAU OF STANDARDS, WASHINGTON, D.C.
February 9, 1950.
Summary—Cellulose nitrate motion picture film in the advanced stages of
decomposition is liable to ignite spontaneously. The danger of such ignition
is reduced by inspecting stored film stocks and removing and destroying all
During the abnormally hot summer of 1949, numerous fires involving cellulose
nitrate motion picture films were reported in New York City and adjacent
areas. These fires occurred in processing and reclamation plants and in
standard film storage facilities. Losses resulting from those fires, other
than those of real property, were severe, for the majority of the films
destroyed were original negatives and master copies, some dating back to the
“silent era.” Due to the fact that these fires occurred either after working
hours or on weekends, no casualties to personnel resulted, although some
firemen were treated for smoke inhalation.
National Archives and Bureau of Standards engineers who investigated the fires
could find no evidence that they were due to the negligence of personnel or
the careless use of cigarettes or matches, but rather they appeared to have
originated in the spontaneous ignition of deteriorated nitrate film. The
summer of 1940 was one of the hottest recorded in the New York area, with the
temperature reaching a maximum of 98ºF. The mean
high temperature for the months of June and July, 1949, was 83.1ºF, as
compared to a normal for the period of 79.3ºF. The rainfall for the entire
month of June was only 0.16 in. in contrast to the normal rainfall of 3.33 in.
for the same period. The lack of rainfall and the unusually high temperatures
of the period seemed to create ideal conditions for the development of
spontaneous ignition in film stores.
to the investigation of these fires it was generally believed that nitrate
film did not ignite spontaneously at temperatures likely to be encountered in
a normal film vault. At the request of the National Archives, the Fire
Protection Section of the National Bureau of Standards instituted an
investigation to determine the possibility of spontaneous ignition as an
inherent hazard in decomposing nitrate film. Samples in various stages of
decomposition were supplied by the National Archives for the purpose of
simulating conditions which may have prevailed at the fire locations. These
samples were stored in a special chamber, the temperature of which was
controlled and recorded. The films were packed in individual cans with each
wrapped in mineral wool to retain the heat of the exothermic decomposition
reaction. The ambient temperature in the chamber was initially 95 ºF and, at
intervals, was increased by small increments. After 17 days of this treatment
one 1,000-ft reel of film, initially in an advanced stage of deterioration,
ignited; the ambient temperature in the chamber at the time was 106 ºF.
Subsequently, with the ambient temperature at 120 ºF, another roll of film
made by the National Bureau of Standards have not yet been completed, but so
far, some important conclusions can be drawn. Self-ignition temperature, which
is dependent upon a number of factors, was not the same for any two samples.
The lowest temperature leading to ignition was 106ºF. Because the number of
samples investigated was small, it is doubtful
Container in which reel of film was placed, showing thermocouple wires.
this is the lowest temperature at which a reel of film can self-ignite. One
reassuring aspect of the results of the tests to date is that no film in good
condition has self-ignited
Reel of Film which had spontaneously ignited (during a
test it the National Bureau of Standards.
the moment, no one can predict what the weather conditions will be during the
coming summer and it is quite possible that other regions may be confronted
with abnormally high temperatures such as prevailed in the Atlantic Coastal
Region during last year. This possibility offers the chance that then will be
a recurrence of regrettable film fires. The hazard should not be
underestimated for, even with abundant water supplies, cellulose nitrate fires
are difficult to combat. Nitrate base film contains oxygen in chemical
combination and does not need a additional oxygen
to sustain combustion. Furthermore, the fumes given off by its combustion are
highly toxic and seriously hamper the fire fighters. They contain oxides of
nitrogen which, if inhaled, can be fatal. Shortage of municipal water supplies
in many areas presents an acute control problem definitely requiring the
constant maintenance of every safeguard.
of Fire Prevention
results obtained in the Bureau of Standards tests indicate that good film does
not self-ignite at ordinary storage temperatures. Therefore, the logical
approach is to remove from storage all film showing signs of deterioration.
Such film can readily be found by regularly scheduled inspection of stored
Temperature during the critical period in which a film
Inspecting personnel should be trained to recognize decomposing film by
appearance, with its condition classified according to the following
categories, in the first stage of deterioration the photographic portion
usually shows an amber discoloration with fading of the picture image. In the
second stage, the emulsion becomes adhesive and the film convolutions tend to
stick together during unrolling. Rolls of third-stage film have annular
portions which are soft, contain gas bubbles, and emit a noxious
odor easily recognizable. In the fourth stage of
deterioration, the entire film is soft, its convolutions welded into a single
mass and frequently its surface is covered with a viscous froth. A strong
noxious odor is given off, unmistakable to
inspection personnel when once identified. In the fifth and final stage, the
film mass degenerates partially or entirely into a brownish acrid powder.
Deteriorated film in the first and second stages is photographically
reproducible. If the matter recorded is important, the film can be copied and
the original disposed of. If the material is not valuable, the film should be
disposed of at once. Adhesiveness prevailing in deteriorating film may cause
the emulsion to become detached from the base while unrolling. This frequently
can be prevented by slowly unrolling the film in a bath of carbon
tetrachloride under precise laboratory control. This should be done only in
adequately ventilated areas. In the third stage, only small portions of the
film may be reproducible. The reproducible portions should be separated, if
valuable, from the rest and copied. After reproduction, the entire original
film should be immediately destroyed. In the fourth and fifth stages, film is
photographically worthless and should be destroyed at once without further
Sample of film in the third stage of decomposition
Sample of film in the fourth stage of decomposition
Sample of film in the fifth stage of decomposition
of stages three, four, and five, designated for disposal should be immediately
submerged in water-filled drums. They should be carried in these drums to a
remote, uninhabited area approved by fire authorities and destroyed by
burning. The ground on which the film is to be burned should be free of brush,
grass, leaves, and combustible litter. Burning should be confined to batches
of not more than 25 lb, as the heat from the burning of large amounts of film
creates a strong updraft which may bear fragments of burning film considerable
distances to endanger neighboring properties.
Under no circumstances should films be burned in an inhabited area or within a
building. The rapid production of gases by burning film makes it extremely
dangerous, particularly if burned in a furnace or confined space. During test
fires in a well vented vault, engineers of the Interagency Advisory Committee
for Nitrate Film Vault Tests have recorded pressures as high as 18
psi. It is readily understandable that no ordinary
furnace structure could withstand this pressure; its breeching would fail and
fill the furnace room with flames and poisonous gases.
Protection of Personnel during Inspection
quite possible in the initial inspection that a relatively high proportion of
film in advanced stages of decomposition may be found.The
opening of cans containing this film may liberate quantities of noxious gases
into the working area. Personnel exposed to them may experience nausea,
headache, and other unpleasant symptoms if the ventilation is inadequate. It
is, therefore, recommended that the personnel working on old film inspection
be given ten-minute rest periods each hour in the outer air.
are to enjoy freedom from film fires during the coming summer, a comprehensive
program of film inspection should begin now so that the task may he completed
before the onset of hot weather. Since film is constantly subject to
decomposition, inspection should be repeated annually, preferably in the
spring. Only by such procedure can we avoid the insidious menace to life and
property hidden in deteriorating motion picture film. Particular attention
should be given to film of unknown quality or of obscure origin.