Always store film in acid-free containers. Acids present in most papers, cardboards and plastics will eventually damage silver halide film. Also, this film must be kept away from chemicals. Even the fumes of duplicating fluids used in most dry copiers can severely damage silver halide film. This will cause deterioration of the images of documents.
Banks can provide a place in some cities to store master copies of microfilm.
These are usually adequate. If banks refuse to store film, search for a storage facility which can, in addition to the above requirements, provide fire and security protection.