It is further defined as an activity that includes one or more of the following diving beyond 40 meters 130 feet, required stage decompression, diving in an overhead environment beyond 130 linear feet from the surface, accelerated stage decompression and or the use of multiple gas mixtures in a single dive.

This lets them stay underwater longer for the same decompression requirement as for air, because less nitrogen is absorbed into the body's tissues.

Similarly, some file systems allow transparent compression and decompression of data, enabling users to store more files on a medium without any special knowledge some file systems encrypt files transparently.

Pure oxygen is mainly used to speed the shallow decompression stops at the end of a military, commercial, or technical dive and is only safe down to a depth of 6 meters (maximum operating depth) before oxygen toxicity sets in.

In technical diving, the diver may carry different equipment for different phases of the dive some breathing gas mixes may only be used at depth, such as trimix and others, such as pure oxygen, which only may be used during decompression stops in shallow water.