This Standard provides requirements for the design, fabrication, inspection, testing, marking, and stamping of pressure vessels for human occupancy, hereafter called PVHO\'s or chambers. This Standard also provides requirements for the design, fabrication, inspection, testing, cleaning, and certification of piping systems for PVHO\'s. A PVHO is a pressure vessel that encloses a human being within its pressure boundary while it is under internal or external pressure, regardless of the pressure magnitude. PVHO\'s include, but are not limited to, submersibles, diving bells, personnel transfer capsules, decompression chambers, recompression chambers, hyperbaric chambers, high altitude chambers, and medical hyperbaric oxygenation facilities. This does not include nuclear reactor containments, pressurized airplane and aerospace vehicle cabins, and caissions.