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A diving chamber is a vessel for human occupation, which may have an entrance that can be sealed to hold an internal pressure significantly higher than ambient pressure, a pressurised gas system to control the internal pressure, and a supply of breathing gas for the occupants.
There are two main functions for diving chambers:

as a simple form of submersible vessel to transport divers underwater and to provide a temporary base and retrieval system in the depths;
as a land, ship, or offshore platform-based hyperbaric chamber or system, to artificially reproduce the hyperbaric conditions under the sea. Internal pressures above normal atmospheric pressure are provided for diving-related applications such as saturation diving and diver decompression, and non-diving medical applications such as hyperbaric medicine. It is also known as a pressure vessel for human occupancy, or PVHO.

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