This document specifies the procedure for the photographic activity and dye coupler reactivity tests. This document is applicable to general photographic enclosure materials such as paper, tissue, cardboard, mat board and plastics. It is also applicable to components of photographic enclosure materials such as adhesives and marking substances, including inks, paints, labels, and tape. This document evaluates possible chemical interactions between enclosures and processed silver-gelatin and colour (dye-gelatin) images, and applies to all storage, display, and transport materials used for photographs whether intended for short or long-term use. A modified version of the document is applicable to diazo images. This document may apply to many historic photographic processes. This document does not apply to other non-silver-gelatin imaging systems. It does not pertain to harmful physical interactions such as blocking (sticking together), dye bleed, adhesive migration, or plasticizer exudation. It does not pertain to important criteria of enclosures such as their inherent chemical stability, physical integrity, and workmanship. Passing the photographic activity test (PAT) does not indicate that a material is archival. This term has no clear definition and is not used in this document. Photo-safe storage enclosures and their components are covered in ISO 18902, which supersedes the PAT and includes passing the criteria of PAT.