While these are two separate courses, they are usually combined into one longer course as they are tightly bound together. Dives learn to plan and carry out a staged decompression dive to a maximum depth of 45M.
As part of this process divers also learn about richer nitrox mixtures than they learned about in the Nitrox course. These richer gases are used during the decompression phase of the dives.
This is the first step for people looking to go on to further technical diving studies for both open circuit scuba diving and CCR diving.