National Archives and Records Service film-vault fire at Suitland, Md. : hearings before a subcommittee of the Committee on Government Operations, House of Representatives, Ninety-sixth Congress, first session, June 19 and 21, 1979 (1979)

163 it had not been operated for approximately 40 minutes prior to the explosion, which effectively eliminates it as a point source of ignition. But there was another avenue as a cause of the fire that we looked at. That is the possibility of a hot metal chip caused by the drill striking a steel structural support in the cement ceiling. This was investigated. The ceiling, itself, was cement, and, most definitely, although I did not find them, I would assume that there are structural supports in there to hold the ceiling and make it more structurally sound. As for work accomplished by Kocharian employees, the following was noted: One, holes had been drilled in the ceilings of vaults 10 through 19; two, tapped metal inserts had been inserted in the holes in vaults 11 through 19 ; three, no inserts had been placed in the holes in vault 10 prior to breaking for lunch. The untapped holes were scraped with a knife, and I could detect no metal in these holes, although there might very well be. Other than completely taking the ceiling apart, I could not tell you for sure. Yet, even if a hot metal chip had been produced by the drilling operation, in my opinion, the following sequence would have been required for it to have acted as a source of ignition. One, considering the environment in the vaults, it would have been most probable that, had such a chip existed, it would have had the highest probability for ignition at the moment it was formed. This would have been the moment it would have had the highest temperature. Two, if it fell to the floor or onto one of the shelves, unless it fell onto a nest of combustible material such as rags or newspapers, it would have immediately begun to cool. Since no such burned or unburned combustible materials were found on the January 2, 1979, inspeetion that I made, and since the fi.rst explosion occurred some 40 minutes after the last drilling operation, it is highly unlikely that such a hot chip was the source of ignition. Three, the third area of interest is the fire marshal's findings of spontaneous combustion. The Prince Georges County fire investigations concluded that the first explosion occurred in vault 8 or vault 9 as a result of spontaneous combustion of the cellulose nitrate film. Although lack of another source of ignition, coupled with the inherently flammable characteristics of decomposing cellulose nitrate film point to spontaneaus combustion as the likely cause, there are some questions that must be addressed to fi.rmly establish this conclusion. The historical literature is quite clear in establishing the ignition and rapid combustion hazards of cellulose nitrate film. In particular, when in advanced stages of decomposition, nitrate film offers the most serious threat of spontaneous combustion. It was noted in a March 1950 article in the Society of Motion Picture and Television Engineers Journal entitled "Spontaneous Ignition of Decomposing Cellulose Nitrate Film," that spontaneous combustion occurred at ambient temperatures of 106° F, in a 1954 test. There are numerous factors, such as temperature, humidity, and physical arrangement that can effect decomposition and probabilitv of ignition. In general, there is no established rule of thumb, and, in fact, there is a distinct lack of current data with regard to the spontaneous combustion of nitrate-based film.