A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. Air is the most common and only natural breathing gas. Other artificial gases either pure gases or mixtures of gases are used in breathing equipment and enclosed habitats such Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where humans cannot safely breathe from the atmosphere. In the armed forces it is sometimes called "CCUBA" (Closed Circuit Underwater Breathing Apparatus). For the military meaning see Armed forces. For the Soviet sports society see Armed Forces (sports society Armed Forces

Contents 1 Basics 2 History of rebreathers 3 Advantages of rebreather diving 3.1 Efficiency advantages 3.2 Feasibility advantages 3.3 Other advantages 4 Parts of a rebreather 4.1 The loop 4.2 Carbon dioxide scrubber 4.2.1 Scrubber failure 4.2.2 Failure prevention 4.3 Effectiveness 4.4 Controlling the mix 4.5 Counterlung 4.6 Bailout 4.7 Casing 5 Main rebreather design variants 5.1 Oxygen rebreather 5.2 Semi-closed circuit rebreather 5.3 Fully closed circuit rebreather 5.4 Rebreathers whose absorbent releases oxygen 5.5 Rebreathers which store liquid oxygen 5.5.1 Cryogenic rebreather 5.6 Other designs 6 Risks and precautions with rebreather diving 7 Sport diving rebreather technology innovations 8 Some makes of rebreather 8.1 See also 9 References 10 External links 10.1 Other information sources 10.2 Rebreather-related forums 10.3 Notable former diving rebreather manufacturers

Basics

Rebreather technology is used in many environments:

• Underwater - where it is sometimes known as CCR = "closed circuit rebreather", "closed circuit scuba" or "semi closed scuba", or CCUBA = "closed circuit underwater breathing apparatus", as opposed to Aqua-Lung-type equipment, which is known as "open circuit scuba". A scuba set is an independent breathing set that provides a scuba diver with the Breathing gas necessary to breathe underwater during Scuba diving. Aqualung was the original name for the first open-circuit scuba diving equipment, developed by Emile Gagnan and Jacques Cousteau in 1943
• Mine rescue and in industry - where poisonous gases may be present or oxygen may be absent. Mine rescue is the very specialized job of rescuing miners and others who have become trapped or injured underground in mines usually in Mining accidents and Disasters
• Space suits - outer space is, for all intents and purposes, a vacuum where there is no oxygen to support life. A space suit is a complex system of Garments equipment and environmental systems designed to keep a person alive and comfortable in the harsh environment of outer space Outer space, often simply called space, comprises the relatively empty regions of the Universe outside the escape velocities of Celestial bodies. This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner.
• Hospital anaesthesia breathing systems - to supply controlled proportions of gases to patients without letting anaesthetic gas get into the atmosphere that the staff breathe. Anesthesia, or anaesthesia (see spelling differences; from Greek grc αν- an-, "without" and grc αἲσθησις
• Submarines and hyperbaric oxygen therapy chambers - where the gas in the habitat must remain safe. A submarine is a Watercraft that can operate independently below water as distinct from a Submersible that has only limited underwater capability Hyperbaric medicine, also known as hyperbaric oxygen therapy (HBOT is the medical use of Oxygen at a higher than Atmospheric pressure. Here the rebreather is big and is connected to the air in the habitat.

This article is mainly about diving rebreathers.

As a person breathes, the body consumes oxygen and makes carbon dioxide. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single A person with an open-circuit breathing set typically only uses about a quarter of the oxygen in the air that is breathed in. The rest is breathed out along with nitrogen and carbon dioxide. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14

The rebreather recirculates the exhaled gas for re-use and does not discharge it to the atmosphere or water. It absorbs the carbon dioxide, which otherwise would accumulate and cause carbon dioxide poisoning. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Hypercapnia or hypercapnea (from the Greek hyper = "above" and kapnos = " Smoke " also known as hypercarbia is It removes the carbon dioxide by a process called scrubbing. A carbon dioxide scrubber is a device which absorbs Carbon dioxide. The rebreather adds oxygen to replace the oxygen that was consumed. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Thus, the gas in the rebreather's circuit remains breathable and supports life.

Nearly always, the oxygen comes from a gas cylinder, and the carbon dioxide is absorbed in a canister full of some suitable absorbent such as a form of soda lime. A gas cylinder or tank is a Pressure vessel used to store Gases at high Pressure. Soda lime is a mixture of Chemicals used in granular form in closed breathing environments such as General anaesthesia, Submarines Rebreathers Some absorbent chemical designed for diving applications are Sofnolime, Dragersorb, or Sodasorb. Soda lime is a mixture of Chemicals used in granular form in closed breathing environments such as General anaesthesia, Submarines Rebreathers The Drägerwerk AG is a German company based in Lübeck with a focus on breathing and protection equipment as well as gas detection and analysis systems Some systems use a prepackaged Reactive Plastic Curtain (RPC) based cartridge: one brand of these RPC cartridges is ExtendAir.

Pure oxygen is not considered to be safe for recreational diving below 6 meters, so recreational rebreathers and many professional diving rebreathers also have a cylinder of diluent gas. A Diluent (also referred to as a dilutant or thinner) is a diluting agent This reduces the percentage of oxygen breathed and enables the unit to be used at greater depths. This diluent cylinder may be filled with compressed air or another diving gas mix such as nitrox or trimix. Nitrox refers to any gas mixture composed (excluding trace gases of nitrogen and oxygen this includes normal Air which is approximately 78% Nitrogen

History of rebreathers

See also: Timeline of underwater technology

Around 1620 in England, Cornelius Drebbel made an early oar-powered submarine. This is a Timeline of Underwater Technology. The entries marked ## are about Decompression tables Pre-industrial England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland Cornelius Jacobszoon Drebbel ( Alkmaar, Holland, 1572 - London, November 7 1633) was the Dutch Inventor A submarine is a Watercraft that can operate independently below water as distinct from a Submersible that has only limited underwater capability Records show that, to re-oxygenate the air inside it, he likely generated oxygen by heating saltpetre (sodium or potassium nitrate) in a metal pan to make it emit oxygen. Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 In Inorganic chemistry, a nitrate is a salt of Nitric acid with an Ion composed of one Nitrogen and three Oxygen atoms That would turn the saltpetre into sodium or potassium oxide or hydroxide, which would tend to absorb carbon dioxide from the air around. An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen That may explain how Drebbel's men were not affected by carbon dioxide build-up as much as would be expected. Hypercapnia or hypercapnea (from the Greek hyper = "above" and kapnos = " Smoke " also known as hypercarbia is If so, he accidentally made a crude rebreather nearly three centuries before Fluess and Davis. ^[1]

In 1853 Professor T. Schwann designed a rebreather in Belgium; he exhibited it in Paris in 1878. The Kingdom of Belgium is a Country in northwest Europe. It is a founding member of the European Union and hosts its headquarters as well as those ^[2]

In 1878 Henry Fleuss invented the first certainly known rebreather using stored oxygen and absorption of carbon dioxide by an absorbent (here rope yard soaked in caustic potash solution), to rescue mineworkers who were trapped by water. Henry Albert Fleuss was a pioneering diving engineer and Master Diver for Siebe Gorman & Co Potassium hydroxide is the Inorganic compound with the formula K[[hydroxide OH]] Mining is the extraction of valuable Minerals or other geological materials from the earth usually (but not always from an Ore body [1]

The Davis Escape Set was the first rebreather which was practical for use and produced in quantity. The Davis Submerged Escape Apparatus (also referred to as DSEA was an early type of Oxygen Rebreather invented in 1910 by Sir Robert Davis, head of It was designed about 1900 in Britain for escape from sunken submarines. Year 1900 ( MCM) was an exceptional Common year starting on Monday (link will display the full calendar of the Gregorian calendar The United Kingdom of Great Britain and Ireland was the formal name of the United Kingdom from 1 January 1801 until 12 April 1927 Various industrial oxygen rebreathers (e. g. the Siebe Gorman Salvus and the Siebe Gorman Proto, both invented in the early 1900's) were descended from it; this link shows a Draeger rebreather used for mines rescue in 1907. The Salvus is a light oxygen Rebreather for industrial use (including by Firemen and in coalmine rescue) or in shallow diving. The Proto is a type of Rebreather that was made by Siebe Gorman. The Drägerwerk AG is a German company based in Lübeck with a focus on breathing and protection equipment as well as gas detection and analysis systems Mine rescue is the very specialized job of rescuing miners and others who have become trapped or injured underground in mines usually in Mining accidents and Disasters

In 1903 to 1907 Professor Georges Jaubert, invented Oxylithe, which is a form of sodium peroxide (Na₂O₂) or sodium dioxide (NaO₂). Sodium peroxide, Na2O2 is the normal product when sodium is burned As it absorbs carbon dioxide it emits oxygen. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single In 1909 Captain S. S. Hall, R. N. , and Dr. O. Rees, R. N. , developed a submarine escape apparatus using Oxylithe; the Royal Navy accepted it. It was used for shallow water diving but never in a submarine escape [2]; it was used in the first filming (1907) of Twenty Thousand Leagues Under the Sea. For the 1954 film starring Kirk Douglas see 20000 Leagues Under the Sea.

The first known systematic use of rebreathers for diving was by Italian sport spearfishers in the 1930s. Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest The 1930s were described as an abrupt shift to more radical and conservative lifestyles as countries were struggling to find a solution to the Great Depression. This practice came to the attention of the Italian Navy, which developed its frogman unit, which affected World War II. The Decima Flottiglia MAS ( Decima Flottiglia M ezzi d' As salto also known as La Decima or Xª MAS) ( Italian for "10th World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including ^[3]

In World War II captured Italian frogmen's rebreathers influenced design of British frogman's rebreathers. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including ^[3] Many British frogmen's breathing sets' oxygen cylinders were German pilot's oxygen cylinders recovered from shot-down German Luftwaffe planes. ( German 'luftvafe is a generic German term for an Air force. Those first breathing sets may have been modified Davis Submarine Escape Sets; their fullface masks were the type intended for the Siebe Gorman Salvus. The Davis Submerged Escape Apparatus (also referred to as DSEA was an early type of Oxygen Rebreather invented in 1910 by Sir Robert Davis, head of The Salvus is a light oxygen Rebreather for industrial use (including by Firemen and in coalmine rescue) or in shallow diving. But in later operations different designs were used, leading to a fullface mask with one big face window. One version had a flip-up single window for both eyes to let the user get binoculars to his eyes when on the surface. Binocular telescopes, or binoculars (also known as field glasses are two identical or Mirror - symmetrical telescopes mounted side-by-side and They used bulky thick diving suits called Sladen suits. The Sladen Suit was a heavy type of British divers' Drysuit made by Siebe Gorman. Early British frogman's rebreathers had rectangular breathing bags on the chest like Italian frogman's rebreathers; later British frogman's rebreathers had a square recess in the top so they could extend further up onto his shoulders; in front they had a rubber collar that was clamped around the absorbent canister, as in the CGI image below. A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas Computer animation Computer-generated imagery (also known as CGI) is the application of the field of Computer graphics or more specifically 3D computer graphics ^[3]

In the early 1940s US Navy rebreathers were developed by Dr. The 1940s decade ran from 1940 to 1949 Events and trends The 1940s was a period between the radical 1930s and the conservative 1950s which also leads the period to be Christian J. Lambertsen for underwater warfare. Christian James Lambertsen, MD, DSc (Hon (b 15 May, 1917) is an American environmental and Diving medicine Dr. Lambertsen, who currently works at the University of Pennsylvania, is considered by the US Navy as "the father of the Frogmen". The University of Pennsylvania (also known as Penn) is a private University located in Philadelphia, Pennsylvania, USA. A frogman is someone who is trained to dive or swim in a military capacity often in combat ^[4][5]

Advantages of rebreather diving

Efficiency advantages

The main advantage of the rebreather over other breathing equipment is the rebreather's economical use of gas. With "open circuit" scuba, the entire breath is expelled into the surrounding water when the diver exhales. A breath inhaled from an open circuit scuba system whose cylinder(s) are filled with ordinary air is about 21%^[6] oxygen. When that breath is exhaled back into the surrounding environment, it has an oxygen level in the range of 15 to 16% when the diver is at atmospheric pressure. ^[6] This leaves the available oxygen utilization at about 25%; the remaining 75% is lost.

At depth, the advantage of a rebreather is even more marked. The amount of CO2 in exhaled gas is not a constant percentage, but a constant partial pressure of about 0. In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume 04bar. The amount of oxygen used from each breath is about the same - so as the ambient pressure increases (as a result of going deeper), the percentage of oxygen used from each breath drops. At 30m (100ft), a diver's exhaled breath contains about 20% oxygen and about 1% CO2.

Feasibility advantages

Long or deep dives using open circuit equipment may not be feasible as there are limits to the number and weight of diving cylinders the diver can carry. A diving cylinder, scuba tank or diving tank is used to store and transport high Pressure Breathing gas as a component of SCUBA (Self-Contained The economy of gas consumption is also useful when the gas mix being breathed contains expensive gases, such as helium. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical In normal use only oxygen is consumed: small volumes of expensive inert gases can be reused for many dives.

Other advantages

Rebreathers produce far fewer bubbles^[6] and make less noise than open-circuit scuba; this can conceal military divers and allow divers engaged in marine biology and underwater photography to avoid alarming marine animals and thereby get closer to them. A scuba set is an independent breathing set that provides a scuba diver with the Breathing gas necessary to breathe underwater during Scuba diving. A frogman is someone who is trained to dive or swim in a military capacity often in combat Marine biology is the scientific study of living Organisms in the Ocean or other marine or Brackish bodies of water Underwater photography is the process of taking Photographs while under water The electronic fully closed circuit rebreather, is able to minimise the proportion of inert gases in the breathing mix, and therefore minimise the decompression requirements of the diver, by maintaining a specific and relatively high oxygen partial pressure at all depths. A decompression stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive to safely eliminate absorbed Inert gases from In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume The breathing gas in a rebreather is warmer and more moist than the dry and cold gas from open circuit equipment making it more comfortable to breathe on long dives and causing less dehydration in the diver.

Parts of a rebreather

The loop

Although there are several design variations of diving rebreather, all types have a gas-tight loop that the diver inhales from and exhales into. The loop consists of components sealed together. The diver breathes through a mouthpiece or a fullface mask (or with industrial breathing sets, sometimes a mouth-and-nose mask). A full-face diving mask is a type of Diving mask that seals the whole of the diver's Face from the water and contains a mouthpiece or Demand valve This is connected to one or more tubes bringing inhaled gas and exhaled gas between the diver and a counterlung or breathing bag. This holds gas when it is not in the diver's lungs. The loop also includes a scrubber containing carbon dioxide absorbent to remove from the loop the carbon dioxide exhaled by the diver. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Attached to the loop there will be at least one valve allowing injection of gases, such as oxygen and perhaps a diluting gas, into the loop. There may be valves allowing venting of gas from the loop.

Most modern rebreathers have a twin hose mouthpiece or breathing mask where the direction of flow of gas through the loop is controlled by one-way valves. Some have a single pendulum hose, where the inhaled and exhaled gas passes through the same tube in opposite directions. The mouthpiece often has a valve letting the diver take the mouthpiece from the mouth while underwater or floating on the surface without water getting into the loop. Many rebreathers have "water traps" in the counterlungs, to stop large volumes of water from entering the loop if the diver removes the mouthpiece underwater without closing the valve, or if the diver's lips get slack letting water leak in. Regardless of whether the rebreather in question has the facility to trap any ingress of water, any training on a rebreather will feature procedures for removing any excess water.

Carbon dioxide scrubber

The exhaled gases are forced through the chemical scrubber which removes the carbon dioxide from the gas mixture and leaves the oxygen and other gases available for re-breathing. ^[6] The active ingredient of the scrubber is often soda lime. Soda lime is a mixture of Chemicals used in granular form in closed breathing environments such as General anaesthesia, Submarines Rebreathers The carbon dioxide passing through the scrubber absorbent is removed when it reacts with the absorbent in the canister; this chemical reaction is exothermic. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called In Thermodynamics, the word exothermic "outside heating" describes a process or reaction that releases Energy usually in the form of Heat, but This reaction occurs along a "front" which is a cross section of the canister, of the unreacted soda lime that is exposed to carbon dioxide-laden gas. This front moves through the scrubber canister, from the gas input end to the gas output end, as the reaction consumes the active ingredients. However, this front would be a wide zone, because the carbon dioxide in the gas going through the canister needs time to reach the surface of a grain of absorbent, and then time to penetrate to the middle of each grain of absorbent as the outside of the grain becomes exhausted. In larger environments, such as recompression chambers, a fan is used to pass gas through the canister.

Scrubber failure

The term "break through" means the failure of the "scrubber" to continue removing carbon dioxide from the exhaled gas mix. There are several ways that the scrubber may fail or become less efficient:

• Complete consumption of the active ingredient ("break through").
• The scrubber canister has been incorrectly packed or configured. This allows the exhaled gas to bypass the absorbent. In a rebreather, the soda lime must be packed tightly so that all exhaled gas comes into close contact with the granules of soda lime and the loop is designed to avoid any spaces or gaps between the soda lime and the loop walls that would let gas avoid contact with the adsorbent. If any of the seals, such as o rings, or spacers that prevent bypassing of the scrubber, are not cleaned or lubricated or fitted properly, the scrubber will be less efficient, or outside water or gas may get in circuit. An o-ring, also known as a packing or a toric joint, is a mechanical Gasket in the shape of a Torus; it is a loop of Elastomer with
• When the gas mix is under pressure caused by depth, the inside of the canister is more crowded by other gas molecules (oxygen or diluent) and the carbon dioxide molecules are not so free to move around to reach the absorbent. In deep diving with a nitrox or other gas-mixture rebreather, the scrubber needs to be bigger than is needed for a shallow-water or industrial oxygen rebreather, because of this effect. Nitrox refers to any gas mixture composed (excluding trace gases of nitrogen and oxygen this includes normal Air which is approximately 78% Nitrogen Among British naval rebreather divers, this type of carbon dioxide poisoning was called shallow water blackout. Hypercapnia or hypercapnea (from the Greek hyper = "above" and kapnos = " Smoke " also known as hypercarbia is A shallow water blackout is a loss of consciousness caused by Cerebral hypoxia towards the end of a breath-hold dive in water typically shallower than five
• A Caustic Cocktail - Soda lime is caustic and can cause burns to the eyes and skin. A "caustic cocktail" is a mixture of water and soda lime that occurs when the "scrubber" floods. It gives rise to a chalky taste, which should prompt the diver to switch to an alternative source of breathing gas and rinse his or her mouth out with water. Air is the most common and only natural breathing gas. Other artificial gases either pure gases or mixtures of gases are used in breathing equipment and enclosed habitats such Many modern diving rebreather absorbents are designed not to produce "cocktail" if they get wet.

Failure prevention

• An indicating dye in the soda lime. A dye can generally be described as a Colored substance that has an affinity to the substrate to which it is being applied It changes the colour of the soda lime after the active ingredient is consumed. For example, a rebreather absorbent called "Protosorb" supplied by Siebe Gorman had a red dye, which was said to go white when the absorbent was exhausted. Siebe Gorman & Company Ltd was a British company which developed Diving equipment and breathing equipment and worked on Commercial diving and Marine Color indicating dye was removed from US Navy fleet use in 1996 when it was suspected of releasing chemicals into the circuit. ^[7] With a transparent canister, this may be able to show the position of the reaction "front". This is useful in dry open environments, but is not useful on diving equipment, where:
  • A transparent canister would likely be brittle and easily cracked by knocks.
  • Opening the canister to look inside would flood it with water or get unbreathable outside gas in circuit.
  • The canister is usually out of sight of the user, e. g. inside the breathing bag or inside a backpack box.
• Temperature monitoring. As the reaction between carbon dioxide and soda lime is exothermic, temperature sensors, most likely digital, along the length of the scrubber can be used to measure the position of the front and therefore the life of the scrubber. ^[8] [3]
• Diver training. Divers are trained to monitor and plan the exposure time of the soda lime in the scrubber and replace it within the recommended time limit. At present, there is no effective technology for detecting the end of the life of the scrubber or a dangerous increase in the concentration of carbon dioxide causing carbon dioxide poisoning. Hypercapnia or hypercapnea (from the Greek hyper = "above" and kapnos = " Smoke " also known as hypercarbia is The diver must monitor the exposure of the scrubber and replace it when necessary.
• Carbon dioxide gas sensors exist, but they are not sensitive enough to be used in a rebreather - the scrubber "break through" occurs quite suddenly and the diver shows symptoms before the sensor indicates a dangerous build-up of carbon dioxide. Even if a sensitive carbon dioxide sensor is developed, it may not be useful as the primary tool for monitoring scrubber life when underwater, because mixed gas rebreathers allow very long dives where long decompression stops may be needed: knowing that the rebreather will begin to deliver a poisonous breathing gas in five minutes may not be useful to a diver needing to carry out an hour or more of decompression stops. A decompression stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive to safely eliminate absorbed Inert gases from Air is the most common and only natural breathing gas. Other artificial gases either pure gases or mixtures of gases are used in breathing equipment and enclosed habitats such

Effectiveness

In rebreather diving, the typical effective duration of the scrubber will be half an hour to several hours of breathing, depending on the granularity and composition of the soda lime, the ambient temperature, the design of the rebreather, and the size of the canister. In some dry open environments, such as a recompression chamber or a hospital, it may be possible to put fresh absorbent in the canister when break through occurs.

Controlling the mix

A basic need with a rebreather is to keep the amount of oxygen in the mix, or more technically known as the partial pressure of oxygen or ppO₂, from getting too low (causing anoxia or hypoxia) or too high (causing oxygen toxicity). In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused

With humans, the urge to breathe is caused by a build-up of carbon dioxide rather than lack of oxygen. When using a rebreather, as the oxygen in circuit is used, the resulting carbon dioxide is removed from the breathing gas by the scrubber, suppressing this natural warning. If not enough new oxygen is being added, the proportion of oxygen may get too little to support life while plenty of gas seems to be in circuit. The resulting serious hypoxia causes sudden blackout with little or no warning. This makes hypoxia a deadly problem for rebreather divers: it was sometimes called "shallow water blackout". Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate

In many rebreathers the diver can control the gas mix and volume in the loop manually by injecting each of the different available gases to the loop and by venting the loop. The loop often has a pressure relief valve to prevent over-pressure injuries caused by over-pressure of the loop.

In some early rebreathers the diver had to manually open and close the valve to the oxygen cylinder to refill the counter-lung each time. In others the oxygen flow is kept constant by a pressure-reducing flow valve like the valves on blowtorch cylinders; the set also has a manual on/off valve called a bypass. The meaning of " blowtorch " varies between Britain and the USA In some modern rebreathers, the pressure in the breathing bag controls the oxygen flow like the demand valve in open-circuit scuba; for example, trying to breathe in from an empty bag makes the cylinder release more gas. Most modern closed-circuit rebreathers have electro-galvanic fuel cell sensors and onboard electronics, which monitor the ppO₂, injecting more oxygen if necessary or issuing an audible warning to the diver if the ppO₂ reaches dangerously high or low levels. An electro-galvanic fuel cell is an electrical device used to measure the concentration of Oxygen gas in Scuba diving and Medical equipment

Counterlung

The counterlung provides for an ambient volume of exhaled air to constantly cycle through the rebreather, much like the volume of air in a persons lung on inhalation. Underwater, the position of the breathing bag, on the chest, over the shoulders, or on the back, has an effect on the ease of breathing. The design of the rebreathers' counterlungs can also affect the swimming diver's streamlining due to location of the counterlungs themselves. Used most typically in Competitive swimming, the streamline position is the position a swimmer takes underwater after pushing off a pool wall Some are designed as over-the-shoulder lungs (e. g. InterSpace Systems Megalodon), while others incorporate the counter lungs into a solid case (e. g. The KISS Classic).

For use out of water, this does not matter so much: for example, in an industrial version of the Siebe Gorman Salvus the breathing bag hangs down by the left hip. The Salvus is a light oxygen Rebreather for industrial use (including by Firemen and in coalmine rescue) or in shallow diving.

A rebreather whose counterlung is rubber and not in an enclosed casing, should be sheltered from sunlight when not in use, to prevent the rubber from perishing due to UV light. Sunlight, in the broad sense is the total spectrum of the Electromagnetic radiation given off by the Sun. Vulcanization (or Vulcanisation refers to a specific curing process of Rubber involving high heat and the addition of Sulfur or other equivalent curatives Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays

Bailout

Some diving rebreather sets include a bailout regulator allowing the user to bail onto open-circuit using his diluent tank. This lets the diver ascend on a separate gas supply. The majority of rebreather trainers teach students to also carry an open-circuit scuba cylinder and regulator as a separate bailout source. Bailout is a key area of discussion for rebreather diving, as when the depth starts to increase the bailout strategy becomes a crucial part of planning particularly for technical diving. Technical diving (sometimes referred to a Tec diving) is a form of Scuba diving that exceeds the scope of Recreational diving (although the vast majority

Bailout provisions are also used in space flight by astronauts doing extravehicular activities (EVAs). The Apollo lunar landing missions used a Portable Life Support System (PLSS) backpack functionally almost identical to a diving rebreather. A Primary (or Portable) Life Support System/Subsystem, or PLSS, is the "backpack" of a Spacesuit. The PLSS provided additional functions required in space: radio communications, suit pressurization and the removal of metabolic heat and water vapor.

Bailout in case the PLSS failed was provided by an oxygen purge system (OPS) similar to an open-circuit scuba system. Like the PLSS, the OPS also maintained suit pressure and removed heat and water vapor. When activated, the OPS provided oxygen to a separate inlet on the pressure suit. A vent valve on a separate suit outlet was manually opened to establish a steady, once-through flow to space, removing CO2, heat and water vapor. Like scuba, the OPS used gas far less efficiently than the PLSS, but as an emergency backup simplicity and reliability were paramount. The OPS was a separate unit mounted on top of the PLSS backpack, immediately behind the astronaut's helmet. The OPS was also used as a backup on tethered EVAs where a spacecraft provided oxygen to the astronaut through an umbilical cable.

Similar systems are now used by Space Shuttle and International Space Station astronauts. NASA 's Space Shuttle, officially called the Space Transportation System ( STS) is the Spacecraft currently used by the United States

Casing

Many rebreathers have their main parts in a hard backpack casing. This casing needs venting to let surrounding water or air in and out to allow for volume changes as the breathing bag inflates and deflates. In a diving rebreather this needs fairly large holes, including a hole at the bottom to drain the water out when the diver comes out of water. The SEFA, which is used for mine rescue, to keep grit and stones out of its working, is completely sealed, except for a large vent panel covered with metal mesh, and holes for the oxygen cylinder's on/off valve and the cylinder pressure gauge. The SEFA is a make of Backpack industrial breathing set formerly made by Sabre Safety. Mine rescue is the very specialized job of rescuing miners and others who have become trapped or injured underground in mines usually in Mining accidents and Disasters A mesh is a flat semi-permeable barrier made of connected strands of Metal, Fiber, or other flexible/ductile material Underwater the casing also serves for streamlining, e. Used most typically in Competitive swimming, the streamline position is the position a swimmer takes underwater after pushing off a pool wall g. in the IDA71 and Cis-Lunar. The word cis-lunar came from Latin and means "on this side of the moon" "not beyond the moon" and may refer to the scuba sets described here

Main rebreather design variants

Oxygen rebreather

This is the oldest type of rebreather and was commonly used by navies from the early twentieth century. The only gas that it supplies is oxygen. As pure oxygen is toxic when inhaled at pressure, oxygen rebreathers are limited to a depth of 6 meters (20 feet); some say 9 meters (30 feet). Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused Oxygen rebreathers are also sometimes used when decompressing from a deep open-circuit dive, as breathing pure oxygen makes the nitrogen diffuse out of the blood more rapidly. A decompression stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive to safely eliminate absorbed Inert gases from

In some rebreathers, e. g. the Siebe Gorman Salvus, the oxygen cylinder has two first stages in parallel. The Salvus is a light oxygen Rebreather for industrial use (including by Firemen and in coalmine rescue) or in shallow diving. One is constant flow; the other is a plain on-off valve called a bypass; both feed into the same exit pipe which feeds the breathing bag. A diving regulator is a Pressure regulator used in a Scuba set that supplies the diver with breathing gas In Rebreather breathing sets a bypass is a hand-operated Valve that can be used to let more Oxygen (or other breathing gas into the breathing system A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas In the Salvus there is no second stage and the gas is turned on and off at the cylinder. Some simple oxygen rebreathers had no constant-flow valve, but only the bypass, and the diver had to operate the valve at intervals to refill the breathing bag as he used the oxygen.

Semi-closed circuit rebreather

Military and recreational divers use these because they provide good underwater duration with fairly simple and cheap equipment. Semi-closed circuit equipment generally supplies one breathing gas such as air or nitrox or trimix. Nitrox refers to any gas mixture composed (excluding trace gases of nitrogen and oxygen this includes normal Air which is approximately 78% Nitrogen The gas is injected at a constant rate. Excess gas is constantly vented from the loop in small volumes.

The diver must fill the cylinders with gas mix that has a maximum operating depth that is safe for the depth of the dive being planned. In Technical diving, the maximum operating depth (MOD of a Breathing gas is the depth at which the Partial pressure of Oxygen (ppO2 As the amount of oxygen required by the diver increases with work rate, the oxygen injection rate must be carefully chosen and controlled to prevent either oxygen toxicity or unconsciousness in the diver due to hypoxia. Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused See also Unconscious mind. Unconsciousness, more appropriately referred to as loss of Consciousness or lack of consciousness is Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate

Fully closed circuit rebreather

Military, photographic and recreational divers use these because they allow long dives and produce no bubbles. Closed circuit rebreathers generally supply two breathing gases to the loop: one is pure oxygen and the other is a diluent or diluting gas such as air, nitrox or trimix.

The major task of the fully closed circuit rebreather is to control the oxygen concentration, known as the oxygen partial pressure, in the loop and to warn the diver if it is becoming dangerously low or high. In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume The concentration of oxygen in the loop depends on two factors: depth and the proportion of oxygen in the mix. Too low a concentration of oxygen results in hypoxia leading to sudden unconsciousness and ultimately death when the oxygen is exhausted. Death is the termination of the biological functions that define living Organisms It refers both to a specific Too high a concentration of oxygen results in oxygen toxicity, a condition causing convulsions, which make the diver spit his regulator out when they occur underwater and can lead to drowning. Drowning is Death as caused by suffocation when a liquid causes interruption of the body's absorption of oxygen from the air leading to Asphyxia.

In fully automatic closed-circuit systems, a mechanism injects oxygen into the loop when it detects that the partial pressure of oxygen in the loop has fallen below the required level. Often this mechanism is electrical and relies on oxygen sensitive electro-galvanic fuel cells called ppO₂ meters to measure the concentration of oxygen in the loop. An electro-galvanic fuel cell is an electrical device used to measure the concentration of Oxygen gas in Scuba diving and Medical equipment An electro-galvanic fuel cell is an electrical device used to measure the concentration of Oxygen gas in Scuba diving and Medical equipment

The diver may be able to manually control the mixture by adding diluent gas or oxygen. Adding diluent can prevent the loop's gas mixture becoming too oxygen rich. Manually adding oxygen is risky as additional small volumes of oxygen in the loop can easily raise the partial pressure of oxygen to dangerous levels.

Rebreathers whose absorbent releases oxygen

There have been a few rebreather designs (e. g. the Oxylite) which had an absorbent canister filled with potassium superoxide, which gives off oxygen as it absorbs carbon dioxide: 4KO₂ + 2CO₂ = 2K₂CO₃ + 3O₂; it had a very small oxygen cylinder to fill the loop at the start of the dive. This system is dangerous because of the explosively hot reaction that happens if water gets on the potassium superoxide. The Russian IDA71 military and naval rebreather was designed to be run in this mode or as an ordinary rebreather.

Rebreathers which store liquid oxygen

If used underwater, the liquid-oxygen tank must be well insulated against heat coming in from the water. As a result, industrial sets of this type may not be suitable for diving, and diving sets of this type may not be suitable for use out of water. They include these types:

• Aerophor. The Blackett's Aerophor is a nitrox semi-closed-circuit Rebreather with liquid gas storage made in England from 1910 onwards for use in mine rescue and other industrial uses
• Aerorlox. See http://www.healeyhero.co.uk/rescue/glossary/aerorlox.htm .
• Cryogenic rebreather: see below.

Cryogenic rebreather

There have been plans for a "cryogenic rebreather". It has a tank of liquid oxygen and no absorbent canister. The carbon dioxide is frozen out in a "snow box" by the cold produced as the liquid oxygen expands to gas as the oxygen is used and is replaced from the oxygen tank.

Such a rebreather called the S-1000 was built around or soon after 1960 by Sub-Marine Systems Corporation. It had a duration of 6 hours and a maximum dive depth of 200 meters of salt water. Its ppO₂ could be set to anything from 0. 2 bar to 2 bar without electronics, by controlling the temperature of the liquid oxygen, thus controlling the equilibrium pressure of oxygen gas above the liquid. The diluent could be either liquid nitrogen or helium depending on the depth of the dive. Liquid nitrogen (liquid density at the Triple point is 0707 g/mL is the liquid produced industrially in large quantities by Fractional distillation of The set could freeze out 230 grams of carbon dioxide per hour from the loop, corresponding to an oxygen consumption of 2 liters per minute. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single If oxygen was consumed faster (high workload), a regular scrubber was needed. See:

• Fischel H. , Closed circuit cryogenic SCUBA, "Equipment for the working diver" 1970 symposium, Washington, DC, USA. Marine Technology Society 1970:229-244.
• Cushman, L. , Cryogenic Rebreather, Skin Diver magazine, June 1969, and reprinted in Aqua Corps magazine, N7, 28, 79.

Other designs

• In the Siebe Gorman Proto the absorbent was in a flexible-walled compartment in the bottom of the breathing bag and not in a canister. The Proto is a type of Rebreather that was made by Siebe Gorman.
• This link describes an experimental drysuit (with built-in hood and fullface mask) and rebreather combination where the drysuit acts as the breathing bag, like in an old Draeger standard diving suit variant which had a rebreather pack attached. A dry suit or drysuit provides Thermal insulation or passive thermal protection to the wearer while immersed in water and is worn by divers, A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas The Drägerwerk AG is a German company based in Lübeck with a focus on breathing and protection equipment as well as gas detection and analysis systems A standard diving dress consists of a metallic ( Copper, Brass or Bronze) Diving helmet, an airline or hose from a Surface supplied
• Some British naval rebreathers (e. g. the Siebe Gorman CDBA) had a backpack weight pouch instead of the diver having a separate weight belt. The Clearance Divers Breathing Apparatus (CDBA is a type of Rebreather made by Siebe Gorman in England. Divers wear weighting systems, weight belts or weights, generally made of Lead, to counteract the Buoyancy of other Diving equipment

Risks and precautions with rebreather diving

Many diver training organizations teach the "diluent flush" technique as a safe way to restore the mix in the loop to a level of oxygen that is neither too high nor too low. This page lists SCUBA Diver training organizations Commercial diving: Surface supplied air training organizations International It only works when partial pressure of oxygen in the diluent alone would not cause hypoxia or hyperoxia, such as when using a normoxic diluent and observing the diluent's maximum operating depth. In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused In Technical diving, the maximum operating depth (MOD of a Breathing gas is the depth at which the Partial pressure of Oxygen (ppO2 The technique involves simultaneously venting the loop and injecting diluent. This flushes out the old mix and replaces it with a known proportion of oxygen from the diluent.

Divers using oxygen rebreathers are advised to flush the system when they start the dive, to get surplus nitrogen out of the system.

In addition to the other diving disorders suffered by divers, rebreather divers are also more susceptible to:

• Sudden blackout due to hypoxia caused by too low a partial pressure of oxygen in the loop. Divers face specific physical and Health Risks when they go Underwater (e In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume A particular problem when using a closed circuit rebreather is the drop in ambient pressure caused by the ascent phase of the dive, which reduces the partial pressure of oxygen to hypoxic levels leading to what is sometimes called deep water blackout. A deep water blackout is a loss of consciousness caused by Cerebral hypoxia on ascending from a deep Freedive or breath-hold dive typically of ten metres or more
• Seizures due to oxygen toxicity caused by too high a partial pressure of oxygen in the loop. An epileptic seizure is caused by excessive and/or hypersynchronous electrical Neuronal activity and is usually self-limiting Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused This can be caused by the rise in ambient pressure caused by the descent phase of the dive, which raises the partial pressure of oxygen to hyperoxic levels. In fully closed circuit equipment, aging oxygen sensors may become "current limited" and fail to measure high partial pressures of oxygen resulting in dangerously high oxygen levels. An electro-galvanic fuel cell is an electrical device used to measure the concentration of Oxygen gas in Scuba diving and Medical equipment
• Disorientation, panic, headache, and hyperventilation due to excess of carbon dioxide caused by incorrect configuration, failure or inefficiency of the scrubber. For psychological condition see Panic attack Panic is a sudden Fear which dominates or replaces thinking and often affects groups of A headache ( cephalalgia in medical terminology is a condition of pain in the Head; sometimes Neck or upper back pain may also be interpreted In Medicine, hyperventilation (or overbreathing) is the state of Breathing faster and/or deeper than necessary bringing about lightheadedness and other Hypercapnia or hypercapnea (from the Greek hyper = "above" and kapnos = " Smoke " also known as hypercarbia is Soda lime is a mixture of Chemicals used in granular form in closed breathing environments such as General anaesthesia, Submarines Rebreathers The scrubber must be configured so that no exhaled gas can bypass it; it must be packed and sealed correctly. Another problem is the diver producing carbon dioxide faster than the absorbent can handle, for example, during hard work or fast swimming. The solution to this is to slow down and let the absorbent catch up. The scrubber efficiency may be reduced at depth where the increased concentration of other gas molecules, due to pressure, stops all the carbon dioxide molecules reaching the active ingredient of the scrubber.
• The rebreather diver must keep breathing in and out all the time, to keep the exhaled gas flowing over the carbon dioxide absorbent, so the absorbent can work all the time. Divers need to lose any air conservation habits that may have been developed while diving with open-circuit scuba. In closed circuit rebreathers, this also has the advantage of mixing the gases preventing oxygen-rich and oxygen-lean spaces developing within the loop, which may give inaccurate readings to the oxygen control system.
• "Caustic cocktail" in the loop if water comes into contact with the soda lime used in the carbon dioxide scrubber. Soda lime is a mixture of Chemicals used in granular form in closed breathing environments such as General anaesthesia, Submarines Rebreathers Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single The diver is normally alerted to this by a chalky taste in the mouth. A safe response is to bail out to "open circuit" and rinse the mouth out.

When compared with Aqua-Lungs, rebreathers have some disadvantages including expense, complexity of operation and maintenance and fewer failsafes. Aqualung was the original name for the first open-circuit scuba diving equipment, developed by Emile Gagnan and Jacques Cousteau in 1943 Fail-safe or fail-secure describes a device or feature which in the event of failure, responds in a way that will cause no harm or at least a minimum of harm A malfunctioning rebreather can supply a gas mixture which cannot sustain life. Various rebreathers try to solve these problems by monitoring the system with electronics, sensors and alarm systems. Many very competent divers have died using rebreathers in accidents, which are often put down to operator error. Rebreathers are generally considered safer in extreme conditions such as deep dives (75m = 246 feet or more) or overhead environments, as they reduce the risk of running out of breathable gas. In scuba diving an Overhead environment is a situation where there is not open water overhead and thus the diver in an emergency cannot escape upwards to atmosphere if his Breathing

The bailout requirement of rebreather diving can sometimes also require a rebreather diver to carry almost as much bulk of cylinders as an open-circuit diver so the diver can complete the necessary decompression stops if the rebreather fails completely. A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas A diving cylinder, scuba tank or diving tank is used to store and transport high Pressure Breathing gas as a component of SCUBA (Self-Contained A decompression stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive to safely eliminate absorbed Inert gases from Some rebreather divers prefer not to carry enough bailout for a safe ascent breathing open circuit, but instead rely on the rebreather, believing that an irrecoverable rebreather failure is very unlikely. This practice is known as alpinism or alpinist diving and is generally maligned due to the perceived extremely high risk of death if the rebreather fails.

Sport diving rebreather technology innovations

Over the past ten or fifteen years rebreather technology has advanced considerably, often driven by the growing market in recreational diving equipment. Innovations include:

• The electronic, fully closed circuit rebreather itself - use of electronics and electro-galvanic fuel cells to monitor oxygen concentration within the loop and maintain a certain partial pressure of oxygen
• Automatic diluent valves - these inject diluent gas into the loop when the loop pressure falls below the limit at which the diver can comfortably breathe. An electro-galvanic fuel cell is an electrical device used to measure the concentration of Oxygen gas in Scuba diving and Medical equipment In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume
• Dive/surface valves or bailout valves - a device in the mouthpiece on the loop which connects to a bailout demand valve and can be switched to provide gas from either the loop or the demand valve without the diver taking the mouthpiece from his or her mouth. An important safety device when carbon dioxide poisoning occurs. Hypercapnia or hypercapnea (from the Greek hyper = "above" and kapnos = " Smoke " also known as hypercarbia is
• Integrated decompression computers - these allow divers to take advantage of the decompression benefits provided by the ideal mix in the loop of a fully closed circuit rebreather. By monitoring the oxygen content of the mix they can work out the inert gas content and generate a schedule of decompression stops. A decompression stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive to safely eliminate absorbed Inert gases from
• Carbon dioxide scrubber life monitoring systems - temperature sensors monitor the progress of the reaction of the soda lime and provide an indication of when the scrubber will be exhausted. Soda lime is a mixture of Chemicals used in granular form in closed breathing environments such as General anaesthesia, Submarines Rebreathers ^[9]

Some makes of rebreather

• Deep and Altus Pursuit rebreather controller system by Narked at 90 An upgrade to the Classic Inspiration rebreather.
• The Davis Submerged Escape Apparatus was the first or nearly the first rebreather to be made in quantity. The Davis Submerged Escape Apparatus (also referred to as DSEA was an early type of Oxygen Rebreather invented in 1910 by Sir Robert Davis, head of
• The "Universal" rebreather was a long-dive derivative of the Davis Submerged Escape Apparatus, intended to be used with the Sladen Suit, which see for more information about it. The Davis Submerged Escape Apparatus (also referred to as DSEA was an early type of Oxygen Rebreather invented in 1910 by Sir Robert Davis, head of The Sladen Suit was a heavy type of British divers' Drysuit made by Siebe Gorman.
• Military rebreathers (VIPER and SIVA) made by Carleton Life Support and the Viper E made by Carleton and Juergensen Defense Corporation
• Russian IDA71 military and naval rebreather
• CDBA = "Clearance Diver's Breathing Apparatus":
  • Siebe Gorman CDBA: see there also for CDMBA, SCBA, SCMBA, UBA
  • A type introduced in 1999 in the Royal Navy, being an update of the BioMarine/Carleton[4] MK16: description; images: [5] [6] [7]
• In the Royal Navy the Carleton CDBA is (as at June 2007) planned to be superseded by the CDLSE = "Clearance Divers' Life Support Equipment" made by Divex in Aberdeen in Scotland. A Clearance Diver was originally a specialist naval diver who used Explosives Underwater to remove obstructions to make harbours and shipping channels safe The Clearance Divers Breathing Apparatus (CDBA is a type of Rebreather made by Siebe Gorman in England. The Royal Navy of the United Kingdom is the oldest of the British armed services (and is therefore known as the Senior Service) The Royal Navy of the United Kingdom is the oldest of the British armed services (and is therefore known as the Senior Service) A Clearance Diver was originally a specialist naval diver who used Explosives Underwater to remove obstructions to make harbours and shipping channels safe Life support, in the medical field refers to a set of therapies for preserving a patient's life when essential body systems are not functioning sufficiently to sustain life unaided Aberdeen ( pronounced; Aiberdeen Obar Dheathain is Scotland 's third most populous city and one of Scotland's 32 local government council Scotland ( Gaelic: Alba) is a Country in northwest Europethat occupies the northern third of the island of Great Britain. It is an electronic closed circuit rebreather allowing diving to 60 meters = 197 feet. ^[10]; Google search for information
• Siebe Gorman Salvus
• The Savox was made by Siebe Gorman. The Salvus is a light oxygen Rebreather for industrial use (including by Firemen and in coalmine rescue) or in shallow diving. Siebe Gorman & Company Ltd was a British company which developed Diving equipment and breathing equipment and worked on Commercial diving and Marine See this link and the image at this link. It was an oxygen rebreather with a use duration of 45 minutes. It was worn in front of the body. It had no hard casing.
• The Blackett's Aerophor is a nitrox semi-closed-circuit rebreather with liquid gas storage made in England from 1910 onwards for use in mine rescue and other industrial uses. The Blackett's Aerophor is a nitrox semi-closed-circuit Rebreather with liquid gas storage made in England from 1910 onwards for use in mine rescue and other industrial uses Nitrox refers to any gas mixture composed (excluding trace gases of nitrogen and oxygen this includes normal Air which is approximately 78% Nitrogen Mining is the extraction of valuable Minerals or other geological materials from the earth usually (but not always from an Ore body
• SEFA is a make of industrial oxygen rebreather with 2 hours duration on a filling. The SEFA is a make of Backpack industrial breathing set formerly made by Sabre Safety.
• SDBA is a type of frogman's oxygen rebreather. SDBA can also mean the Singapore Dragon Boat Association The SDBA is a type of Frogman 's Rebreather breathing set It has a nitrox variant called ONBA. Nitrox refers to any gas mixture composed (excluding trace gases of nitrogen and oxygen this includes normal Air which is approximately 78% Nitrogen
• FROGS (= Full Range Oxygen Gas System) is the make of frogman's oxygen rebreather which has been used in France since 15 October 2002: see this link (in French): image at this link: it is made by the diving gear makers Aqualung: see this link for more information. A frogman is someone who is trained to dive or swim in a military capacity often in combat Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the
• Some military rebreathers (for example the US Navy MK-25 and the MK-16 mixed-gas rebreather), and the Phibian CCS50 and CCS100 rebreathers, were developed by Oceanic. Phibians are a Fictional race in the Dune universe first mentioned in Chapterhouse Dune. (Stuart Clough of Undersea Technologies developed the Phibian's electronics package [8]. Carmellan Research is or was a firm who developed automatic Rebreathers for Scuba diving. Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical )
• The current US Navy Mark 16 Mod 2 (Explosive Ordinance Disposal) and Mark 16 Mod 3 (Naval Special Warfare) units use the Juergensen Defense Corporation Mark V Control System.
• The KISS line of manually operated closed circuit rebreathers designed by Gordon Smith of Jetsam Technologies
• Oceanic developed the Phibian CCS50 and CCS100 rebreathers; Stuart Clough of Undersea Technologies developed the Phibian's electronics package. Oceanic is a company which currently designs and manufactures sport-type Scuba gear Phibians are a Fictional race in the Dune universe first mentioned in Chapterhouse Dune. Carmellan Research is or was a firm who developed automatic Rebreathers for Scuba diving. Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical [9]. They have developed military rebreathers, for example the US Navy MK-25 and the MK-16 mixed-gas rebreather. There were unconfirmed reports that Oceanic was going to bring out a new rebreather around October 2006. [10].

See also

• Escape set
• SCBA (surface-only (industrial) rebreathers)

References

External links

Other information sources

• British Sub-Aqua Club - BSAC Technical Diving Resource Centre
• CCR Rebreather Cave diving
• DIRrebreather a website dedicated to rebreather in the DIR philosophy
• Diver Dave's Rebreather Tear-Down Pages. The Historical Diving Society was formed in the United Kingdom in 1990 to preserve the history of Diving and its equipment It has many detailed photographs of rebreathers and their components.
• Images of LAR-6 and LAR-7 and FGT II and LAR V rebreathers, and other combat frogman's kit
• Explanation and video from Popular Mechanics
• Richard Pyle's rebreather page
• www.rebreather-diving.info, a web site dedicated to rebreather safety, support
• RebreatherPro Jill Heinerth's interactive multimedia rebreather diving resource
• The Rebreather Site, including long lists of types of rebreathers, and images
  • which includes: database with 400 rebreathers data and pictures of units from all over the world
• A history of closed circuit oxygen underwater breathing apparatus, published in 1970, plenty of images, including mountaineering rebreathers, may be slow to download
• Russian sites:
  • Page in Russian describing the images at the next link. (Click each thumbnail to get a fullsized image).
  • Links to images of old and modern Russian rebreathers
  • Some photos of various Soviet-Russian rebreathers (text in Russian)
• Teknosofen homepage - General rebreather theory and rebreather tear-downs
• TMIShop.com a website dedicated to rebreather information dissemination
• TR300 SCR/mCCR homebuild Rebreathers
• Rebreather Articles: English and French articles about rebreathers (Cedric Verdier)
• 100 Dollar Rebreather - Rebreather built from a hot water bottle
• Shallow Water Blackout

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• List of links to rebreather manufacturers' websites

Rebreather-related forums

• ScubaMagazine.net Community forum, A large multimedia driven rebreather diving community
• RebreatherWorld ([11] forums here, [12] info links page here) An online rebreather forum and community
  • Rebreatherworld list of links to rebreather manufacturers

Notable former diving rebreather manufacturers

• Cis-Lunar - made closed-circuit automatic rebreathers, now operated by Juergensen Marine. A hot water bottle is a container filled with hot water and sealed with a stopper used to provide warmth typically whilst in Bed, but also for the application of heat The word cis-lunar came from Latin and means "on this side of the moon" "not beyond the moon" and may refer to the scuba sets described here
• Siebe Gorman, see also Siebe Gorman. Siebe Gorman & Company Ltd was a British company which developed Diving equipment and breathing equipment and worked on Commercial diving and Marine Important in diving history, but now closed down.

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