What is a Decompression Chamber?
A sealable diving chamber, closed bell or dry bell is a pressure vessel with hatches large enough for people to enter and exit, and a compressed breathing gas supply to raise the internal air pressure. Such chambers provide a supply of oxygen for the user, and are usually called hyperbaric chambers whether used underwater or at the water surface or on land to produce underwater pressures. However, some use submersible chamber to refer to those used underwater and hyperbaric chamber for those used out of water. There are two related terms which reflect particular usages rather than technically different types:
- Decompression chamber, a hyperbaric chamber used by surface-supplied divers to make their surface decompression stops
- Recompression chamber, a hyperbaric chamber used to treat or prevent decompression sickness.
When used underwater there are two ways to prevent water flooding in when the submersible hyperbaric chamber’s hatch is opened. The hatch could open into a moon pool chamber, and then its internal pressure must first be equalised to that of the moon pool chamber. More commonly the hatch opens into an underwater airlock, in which case the main chamber’s pressure can stay constant, while it is the airlock pressure which shifts. This common design is called a lock-out chamber, and is used in submarines, submersibles, and underwater habitats as well as diving chambers.