Since 1977, the American Society of Mechanical Engineers PVHO committee has published standards governing the construction of a number of devices which are defined as Pressure Vessels for Human Occupancy. The current standard is PVHO-1-2007.
List of PVHO types
Nuclear reactor containments, aerospace cabins, caissons or mild hyperbaric chambers are not considered to be PVHOs according to the standard.
References
Pressure vessel for human occupancy Wikipedia(Text) CC BY-SA