Inergen

Because water is just as bad for film stock as is fire or smoke, there are no water pipes anywhere inside the vaults. Instead, the Academy utilizes a fire-supression system called Inergen, which instantly converts oxygen in the air to carbon dioxide. That leaves no fuel in the air for fire, but enough oxygen for someone inside the vaults to breathe long enough to escape.

The Academy keeps this phalanx of tanks in the basement of the building, always at the ready to completely fill a vault with Inergen in the case of a fire. However, two different sensors in the vault must both be triggered in order to release the material, to prevent against a costly false alarm.