The ASME B31.12 standard includes a list of materials in Annex 6.1 that are suitable for hydrogen piping. If you want to use materials not on this list, you must conduct tests to ensure they meet the standard's requirements, including checks on mechanical properties, the pipe manufacturing process, heat treatment, and quality control. However, some European steel grades (EN) that are not listed in ASME B31.12 might not need extra testing because