In order to be accepted into the Security Copy Depository, microfilm must meet certain national standards. These include requirements that the microfilm be made of high quality silver halide and contain no more than six splices per reel. Additionally, microfilm with a retention period of 100 years or more must be treated with polysulfides to protect against microspotting.
The Depository has a capacity of about 500,000 reels of microfilm. These records are generally accessed only to make copies for agencies in cases when working copies were destroyed or worn out. Key records can be replaced in a short period of time in the event of a disaster. For security reasons, access to this vault is limited to a small number of Archives personnel.