Quote :
“Film cans are generally manufactured from a stable plastic or metal, usually steel or aluminium. The can lid is often a tight fit but does not seal the can completely allowing a small degree of equilibrium between the external environment and the internal microclimate. Film cans have a buffering effect on the rate of change of the internal microclimate in relation to the storage conditions. Temperature is buffered less than relative humidity.”
“One of the major issues in film preservation is the autocatalytic decomposition reaction of cellulose ester polymers used as the film base. In this reaction the acids, created as a byproduct, will accelerate the reaction rate at any given temperature2. The most commonly used and effective method of controlling the rate of the decomposition reaction, and thus the amount of acid in the film, is by low temperature and low relative humidity storage. However this can be very expensive for archives in poorer countries, not only in establishing suitable vaults and plant, but also in the ongoing running costs.”
See document for reference and more information:
AMIA: Vented Film Cans Research