Guide to Decompression Procedures . Are you finding your no- decompression limits (NDLs) a limiting factor to dives? Do you have to ascend sooner than you would like? As sport divers, planned decompression is not something that we do or have been taught. The TDI Decompression Procedures Course prepares you for planned staged decompression diving. With a maximum operating depth of 45 meters/150 feet, this course is your first step beyond the normal sport diving limits.