Forty years ago, employees of the National Archives and Records Service experienced the thing they had been working for decades to prevent: some of the highly flammable nitrate-based film held in the federal complex in Suitland, Maryland, had caught fire, the blaze ultimately destroying 12.6 million feet of historical newsreel footage and outtakes that had been donated by Universal Pictures.

The fire broke around lunchtime on December 7, 1978 in the film vaults, as Andrew Smith, a records analyst for the National Archives and Records Administration, recounted this month for the Unwritten Record blog.

The structures, called buildings A, B, and C, had been created specifically to store the fire-prone film in 1945. When Universal agreed to donate its library— a mix of nitrate and acetate footage covering 1929 to 1967—to the National Archives in 1970, other improvements, including a high-speed sprinkler system, were added to the vaults.

All seemed fine until an earlier fire broke out in Building A in 1977, which destroyed 800,000 feet of the March of Time newsreel footage. Following the fire, the National Archives decided to update the temperature and humidity systems in all of the buildings as a precaution. During the work, the contractors, tasked at upgrading the air conditioning and increasing insulation in Building A, fatefully disabled a third of its sprinkler heads.

According to a government report, it’s suspected that the blaze began when one of the contractors’ power tools sparked. The contractor and fire department, however, placed the blame on an old air conditioning system that was reported low on Freon months earlier. They claimed the malfunctioning air conditioner in a Building A vault allowed the temperature and humidity to reach dangerous levels, setting off the blaze.

Whatever the case, the disabled sprinklers were no help. And as firefighters moved through the building, looking for anyone trapped inside, they opened the fireproof doors, allowing the flames to spread.

The fire destroyed most of volumes 14 to 17, which covered the years 1941 to 1945. Despite the loss, written records and scripts from the newsreels still survive. The remainder of the newsreel collection, consisting of some 15,000 reels, was also duplicated in a massive preservation project completed in 2010. The buildings themselves were demolished in the early 2000s.

While accidents and mismanagement might have contributed to the incident, the accident was far from an isolated incident when it came to nitrate film. In fact, as Liz Logan at Hyperallergic details, it’s surprising any nitrate film exists at all today. The film was used from the birth of cinema in the late 1800s up until the 1940s when safer acetate film came on the scene. Nitrate film is an early form of plastic, and once it ignites, it produces its own oxygen, which is what makes it so flammable.

The very first recorded nitrate-related fire incident occurred in 1896. Movie houses occasionally burned due to careless handling of the film, and even film studios couldn’t keep the stuff safe—RKO, Universal, and Warner Brothers all had fires decimate film vaults. Other cultural institutions have also suffered major fires from the film, including Cinematheque Francaise, National Film Board of Canada, George Eastman House, and the Museum of Modern Art. Because of this, some vaults and institutions have intentionally burned their nitrate film after transferring its content to other media. But that doesn’t mean nitrate film has been entirely put out of circulation. Some is still in good shape and can be used in a projector, popping up in places like the Nitrate Picture Show at the Eastman Museum.

Is preserving the stuff worth the risk? Connoisseurs believe the film is bright and detailed in a way other media simply isn’t. Dennis Bartok, manager of the Egyptian Theatre, which installed a fireproof projection booth, and has screened nitrate films including Black Narcissus and Casablanca during the TCM Classic Film Festival, tells Beth Accomando at NPR that the old-style film stock really does make a difference. “So, people will compare them to an illuminated manuscript or something like that,” he says. “All I can say is watching Black Narcissus really is a spiritual experience for people who love cinema.”

And the stuff may not be (quite) as fragile as advertised. In a 2015 oral history, Paul Spehr, former assistant chief of the Motion Picture Broadcasting and Recorded Sound Division at the Library of Congress, says the Library never had a fire during his 37 years there. Asked what people should know about the film, he said, "Well, it lasts longer, but I think people understand it now. Up to the time I retired 20 years ago, the assumption was that it was all going to be gone by 2000. And it's not all gone, it's still there, and it's still showing up."