History of decompression research and development gets too high when compared to the ambient pressure. These bubbles, and products of injury caused by the bubbles, can cause damage to tissues known as "decompression sickness" or "the bends". The immediate goal of controlled decompression is to avoid development of symptoms of bubble formation in the tissues of the diver, and the long-term goal is to also avoid complications due to sub-clinical decompression injury. The symptoms of decompression sickness are known to be caused by damage resulting from the formation and growth of bubbles of inert gas within the tissues and by blockage of arterial blood supply to
Scuba set carry larger sets of three or four cylinders and most rebreathers. Additional cylinders for decompression can be sling mounted at the diver's sides. It is also possible to use a plain backpack harness to support the set, either with a horse-collar buoyancy compensator, or without any buoyancy compensator. This was the standard arrangement before the introduction of the buoyancy compensator, and is still used by some recreational and professional divers when it suits the diving operation. Surface-supplied divers are generally required to carry an emergency gas supply, also known as a bailout set, which is usually back-mounted open circuit scuba