The TDI Trimix course provides the training required to competently and safely utilize breathing gases containing helium for dives that require staged decompression, utilizing nitrox and/or oxygen mixtures during decompression to a maximum depth of 60 meters (200 feet). The objective of this course is to train divers in the benefits, hazards, and proper procedures of utilizing custom oxygen/helium/nitrogen mixtures as breathing gases. Gas mixes are not to have any less than 18% oxygen.