Technical diving is a term used to describe all diving methods that exceed the limits imposed on depth and/or immersion time for recreational scuba diving.
Technical diving often involves the use of special gas mixtures (rather than compressed air) for breathing.
The type of gas mixture used is determined either by the maximum depth planned for the dive or by the length of time that the diver intends to spend underwater.
While the recommended maximum depth for conventional scuba diving is 130 feet, technical divers may work in the range of 170 feet to 350 feet, sometimes even deeper.
Technical diving almost always requires one or more mandatory decompression «stops» upon ascent,
during which the diver may change breathing gas mixes at least once. Decompression stops are necessary to allow gases
that have accumulated in the diver’s tissues (primarily nitrogen) to be released in a slow and controlled manner.