The usage of enclosures is the easiest method of preserving photographic materials from being damaged through handling and light exposure. All protective materials should pass the "Photographic Activity Test" (PAT) as described both by the American National Standards Institute (ANSI) in standard IT9.2–1988, and the International Organization for Standardization (ISO) in standard 18916:2007(E), "Photography – Processed Photographic Materials – Photographic Activity Test for Enclosure Materials". The PAT is an archival science test that determines what kind of storage enclosures will preserve, prolong, and/or prevent further deterioration.