diving chamber diving chamber 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. "hyperbaric chamber" redirects here. not to be confused with hypobaric chamber or hyperbaric medicine. diving chamberthe decompression chamber at the neutral buoyancy labacronymddcother namesdecompression chamberdeck decompression chamberrecompression chamberhyperbaric chambersaturation chamberusesdiver trainingtherapeutic recompressionsurface decompressionsaturation divingdiving physiology research 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. basic types of diving chambers there are two basic types of submersible diving chambers, differentiated by the way in which the pressure in the diving chamber is produced and controlled. open diving bell the historically older open diving chamber, known as an open diving bell or wet bell, is in effect a compartment with an open bottom that contains a gas space above a free water surface, which allows divers to breathe underwater. the compartment may be large enough to fully accommodate the divers above the water, or may be smaller, and just accommodate head and shoulders. internal air pressure is at the pressure of the free water surface, and varies accordingly with depth. the breathing gas supply for the open bell may be self-contained, or more usually, supplied from the surface via flexible hose, which may be combined with other hoses and cables as a bell umbilical. an open bell may also contain a breathing gas distribution panel with divers' umbilicals to supply divers with breathing gas during excursions from the bell, and an on-board emergency gas supply in high-pressure storage cylinders. this type of diving chamber can only be used underwater, as the internal gas pressure is directly proportional to the depth underwater, and raising or lowering the chamber is the only way to adjust the pressure. hyperbaric 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, at the water surface or on land to produce underwater pressures. however, some use the term submersible chamber to refer to those used underwater and hyperbaric chamber for those used out of water. there are two related terms that 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 that shifts. this common design is called a lock-out chamber, and is used in submarines, submersibles, and underwater habitats as well as diving chambers. another arrangement utilises a dry airlock between a sealable hyperbaric compartment and an open diving bell compartment (so that effectively the whole structure is a mixture of the two types of diving chamber). when used underwater all types of diving chamber are attached to a diving support vessel by a strong cable for raising and lowering and an umbilical cable delivering, at a minimum, compressed breathing gas, power, and communications, and all need weights attached or built in to overcome their buoyancy. the greatest depth reached using a cable-suspended chamber is about 1500 m; beyond this the cable becomes unmanageable. related equipment in addition to the diving bell and hyperbaric chamber, related diving equipment includes the following: underwater habitat: consists of compartments operating under the same principles as diving bells and diving chambers, but placed in a fixed position on the sea floor for long-term use. submersibles and submarines differ in being able to move under their own power. the interiors are usually maintained at surface pressure, but some examples include air locks and internal hyperbaric chambers. there is also other deep diving equipment that has atmospheric internal pressure, including: bathysphere: name given to an experimental deep-sea diving chamber of the 1920s and 1930s. benthoscope: a successor to the bathysphere built to go to greater depths. bathyscaphe: a self-propelled submersible vessel able to adjust its own buoyancy for exploring extreme depths. atmospheric diving suit: a roughly anthropomorphic submersible for a single occupant, which maintains an internal pressure close to normal sea level atmospheric pressure underwater use as well as transporting divers, a diving chamber carries tools and equipment, high pressure storage cylinders for emergency breathing gas supply, and communications and emergency equipment. it provides a temporary dry air environment during extended dives for rest, eating meals, carrying out tasks that can't be done underwater, and for emergencies. diving chambers also act as an underwater base for surface supplied diving operations, with the divers' umbilicals (air supply, etc.) attached to the diving chamber rather than to the diving support vessel. diving bells diving bells and open diving chambers of the same principle were more common in the past owing to their simplicity, since they do not necessarily need to monitor, control and mechanically adjust the internal pressure. secondly since internal air pressure and external water pressure on the bell wall are almost balanced, the chamber does not have to be as strong as a pressurised diving chamber (dry bell). the air inside an open bell is at the same pressure as the water at the air-water interface surface. this pressure is constant and the pressure difference on the bell shell can be higher than the external pressure to the extent of the height of the air space in the bell. a wet diving bell or open diving chamber must be raised slowly to the surface with decompression stops appropriate to the dive profile so that the occupants can avoid decompression sickness. this may take hours, and so limits its use. submersible hyperbaric chambers submersible hyperbaric chambers known as closed bells or personnel transfer capsules can be brought to the surface without delay by maintaining the internal pressure and either decompressing the divers in the chamber on board the support vessel, or transferring them under pressure to a more spacious decompression chamber or to a saturation system, where they remain under pressure throughout the tour of duty, working shifts under approximately constant pressure, and are only decompressed once at the end. the ability to return to the surface without in-water decompression reduces the risk to the divers if the weather or compromised dynamic positioning forces the support vessel off station. a diving chamber based on a pressure vessel is more expensive to construct since it has to withstand high pressure differentials. these may be bursting pressures as is the case for a dry bell used for saturation diving, where the internal pressure is matched to the water pressure at the working depth, or crushing pressures when the chamber is lowered into the sea and the internal pressure is less than ambient water pressure, such as may be used for submarine rescue. rescue bells are specialized diving chambers or submersibles able to retrieve divers or occupants of diving chambers or underwater habitats in an emergency and to keep them under the required pressure. they have airlocks for underwater entry or to form a watertight seal with hatches on the target structure to effect a dry transfer of personnel. rescuing occupants of submarines or submersibles with internal air pressure of one atmosphere requires being able to withstand the huge pressure differential to effect a dry transfer, and has the advantage of not requiring decompression measures on returning to the surface, allowing a more rapid turnaround to continue the rescue effort. out of water use hyperbaric chambers are also used on land and above the water: to take surface supplied divers who have been brought up from underwater through their remaining decompression as surface decompression either after an ambient pressure ascent or after transfer under pressure from a dry bell. (decompression chambers) to train divers to adapt to hyperbaric conditions and decompression routines and test their performance under pressure. to treat divers for decompression sickness (recompression chambers) to treat people using raised oxygen partial pressure in hyperbaric oxygen therapy for conditions unrelated to diving. in saturation diving life support systems in scientific research requiring elevated gas pressures. hyperbaric chambers designed only for use out of water do not have to resist crushing forces, only bursting forces. those for medical applications typically only operate up to two or three atmospheres absolute, while those for diving applications may go to six atmospheres or more. lightweight portable hyperbaric chambers that can be lifted by helicopter are used by military or commercial diving operators and rescue services to carry one or two divers requiring recompression treatment to a suitable facility. decompression chamber a decompression chamber, or deck decompression chamber, is a pressure vessel for human occupancy used in surface supplied diving to allow the divers to complete their decompression stops at the end of a dive on the surface rather than underwater. this eliminates many of the risks of long decompressions underwater, in cold or dangerous conditions. a decompression chamber may be used with a closed bell for decompression after bounce dives, following a transfer under pressure, or the divers may surface before completing decompression and be recompressed in the chamber following stringent protocols to minimise the risk of developing symptoms of decompression sickness in the short period allowed before returning to pressure. two united states navy sailors inside a decompression chamber about to undergo training one person chamber control panel of a basic deck decompression chamber the medical lock of a basic deck decompression chamber with the door closed exterior view of a basic deck decompression chamber transportable decompression chamber divers breathing oxygen during surface decompression operating a chamber from the control panel hyperbaric treatment chamber a hyperbaric treatment chamber is a hyperbaric chamber intended for, or put into service for, medical treatment at pressures above the local atmospheric pressure. hyperbaric oxygen therapy chamber monoplace chamber for clinical hyperbaric oxygen treatment internal view of a multiplace chamber for hyperbaric oxygen therapy, showing the airtight door leading to the entry lock. pressure release valve and pressure gauge inside a flexible low pressure hyperbaric oxygen therapy chamber inside of a flexible low pressure hyperbaric oxygen therapy chamber a hyperbaric oxygen therapy chamber is used to treat patients, including divers, whose condition might improve through hyperbaric oxygen treatment. some illnesses and injuries occur, and may linger, at the cellular or tissue level. in cases such as circulatory problems, non-healing wounds, and strokes, adequate oxygen cannot reach the damaged area and the body's healing process is unable to function properly. hyperbaric oxygen therapy increases oxygen transport via dissolved oxygen in serum, and is most efficacious where the haemoglobin is compromised (e.g. carbon monoxide poisoning) or where the extra oxygen in solution can diffuse through tissues past embolisms that are blocking the blood supply as in decompression illness. hyperbaric chambers capable of admitting more than one patient (multiplace) and an inside attendant have advantages for the treatment of decompression sickness (dcs) if the patient requires other treatment for serious complications or injury while in the chamber, but in most cases monoplace chambers can be successfully used for treating decompression sickness. rigid chambers are capable of greater depth of recompression than soft chambers that are unsuitable for treating dcs. recompression chamber further information: decompression sickness § treatment recompression chamber a recompression chamber is a hyperbaric treatment chamber used to treat divers suffering from certain diving disorders