It is described in the safety standard (ISGOTT 7.2 [Measuring and Sampling ]) that "it may be necessary to prevent or minimize the release of vapour from the cargo tank headspace during measurement and sampling operations", therefore, by fitting MMC Portable Cargo Liquid Sampling device [ Cargo Sampler ] to the Vapor Lock Valves (which is installed on board), it prevents the electrification of static electricity, then the safety/easy sampling operation can be achieved without releasing the dangerous vapor from the tank.