ISO 15364:2007 applies to pressure-vacuum relief valves protecting marine vessel systems, including cargo tanks, which may be subject to gas/vapour pressure or vacuum beyond the design parameters of the system/tank. ISO 15364:2007 specifies the minimum requirements for performance and testing of pressure-vacuum relief valves, with emphasis on selection of materials, internal finish and surface requirements for pressure-vacuum valves installed on cargo tanks in tankers (see Annex A). It specifies design and in-service performance criteria, operational testing and maintenance requirements.Certification to ISO 15364:2007 does not imply suitability for any given installation; it indicates that certain minimum requirements have been considered and that information necessary for determination of suitability is provided to the buyer of the equipment.