Using the bubble test procedure, vacuum leak detection units of the VSP series allow a fast and safe leak testing of the welding seams of containers, pipes and many other welded structures. With this testing method even castings can be checked for continuous discontinuities. VSP leak detection units and vacuum boxes are used for leak testing especially in cases when the test piece is accessible only from one side or if it is an open construction (such as the bottom of tanks or collecting basins). Under practical test conditions, the realizable leak detection limit of the bubble test procedure is approx. between 10-5 and 10-4 Pa*m3/s (10-4 to 10-3 mbar*l/s).