Diving regulator 460952 225503404 2008-07-14T01:11:28Z Gene Hobbs 3121896 /* External links */ add link: "How stuff works" <!-- Image with unknown copyright status removed: [[Image:ATMB2S.jpg|right|350px|thumb|Atomic Aquatics B2 Regulator]] --> A '''diving regulator''' is a [[pressure regulator]] used in a [[scuba set]] that supplies the diver with breathing gas at ambient pressure from one or more [[diving cylinder]]s. The gas may be air or one of a variety of specially blended [[breathing gas]]es. A gas pressure regulator has one or more valves in series, which let the gas out of a [[gas cylinder]] in a controlled way, lowering air pressure at each stage. The terms "regulator" and "demand valve" are often used interchangeably, but a demand valve is the part of a regulator that delivers gas to the diver's mouth. <!-- does this need to be here? --> For the history of the diving regulator, see [[Timeline of underwater technology]]. =Parts of a diving regulator= [[Image:Reg firststage.jpg|thumb|right|A diving regulator A-clamp type first stage]] The parts of a regulator are described in downstream order as following the gas flow from the cylinder to its final use. ==Fastening the regulator to the cylinder or cylinder block== [[Image:Diving regulator DIN first stage.jpg|thumb|right|A [[Deutsches Institut für Normung|DIN]] fitting stage with 2 medium pressure and 1 high pressure hose]] In an open-circuit [[scuba set]], the first-stage of the regulator has an [[A-clamp]], also known as a yoke, or a [[Deutsches Institut für Normung|DIN]] fitting to connect it to the [[pillar valve]] of the [[diving cylinder]]. Yoke valves are the most common type by far; it clamps an open hole on the regulator against an open hole on the cylinder. This connection is made gas pressure tight with an [[O-ring]]. The DIN fitting is a type of direct screw-in connection to the cylinder. While less common worldwide, the DIN system has the advantage of withstanding greater pressure and is very common in central Europe. Most yoke-type valves are of the K-valve, which is a simple on-off valve. In the mid-1960s, J-valves were widespread. J-valves contain a spring-operated shutoff that is triggered when tank pressure falls to 300-500 psi, causing breathing resistance and warning the diver that he or she is dangerously low on air. The reserve air is released by pulling a reserve lever on the valve. J-valves fell out of favor with the introduction of pressure gauges, which allow divers to keep track of their air underwater, especially as the valve-type are subject to accidental release of reserve air and increase the cost and servicing of the valve. <!-- Image with unknown copyright status removed: [[Image:F17b.jpg|thumb|200px|right|Suunto pressure and depth gauge]] --> [[Image:diving regulator contents guage.JPG|thumb|100px|right|A [[depth gauge]] and standard contents gauge]] ==Pressure gauge== To monitor breathing gas pressure in the diving cylinder, a diving regulator usually has a ''high pressure'' hose leading to a ''contents gauge'' (also called ''pressure gauge''). The port for this hose leaves the first-stage upstream of all pressure-reducing valves. The ''contents gauge'' is a [[pressure gauge]] measuring the gas pressure in the [[diving cylinder]] so the diver knows how much gas remains in the cylinder. It is also known as ''submersible pressure gauge'' or ''SPG''. There are several types of contents gauge:- ===Standard type=== This is an [[analog (signal)|analogue]] gauge that can be held in the palm of a hand and is connected to the ''first stage'' by a ''high pressure hose''. It displays with a pointer moving over a dial. Sometimes they are fixed in a ''console'', which is a [[plastic]] or [[rubber]] case that holds the air pressure gauge and also a [[depth gauge]] and/or a [[dive computer]] and/or a [[compass]]. ===Button gauges=== These are coin-sized analogue gauges connected directly to the ''first stage''. They are often used on decompression cylinders. Due to their small size, it can be difficult to read the gauge to a resolution of less than 20 bar / 300 psi. ===Air integrated computers=== Some [[dive computer]]s are designed to measure and display and monitor pressure in the [[diving cylinder]]. This can be very beneficial to the diver, but if the [[dive computer]] fails, the diver can no longer monitor his or her gas reserves. Most divers using a gas-integrated computer will also have a standard air pressure gauge. The computer is either connected to the first stage by a ''high pressure hose'', or has two parts, the pressure transducer on the first stage and the display at the wrist or console, which communicate by radio link; the signals are encoded to eliminate the risk of one diver's computer picking up a signal from another diver's transducer, or radio interference from other sources. ===Mechanical reserve valves=== In the past, some types of diving cylinder had a mechanical reserve valve that restricted air flow when the pressure was below 500 psi. Alerted to having a low gas supply the diver would pull a lever to open the reserve valve and surface using the reserve gas. These valves are known as "J valves" due to the letter J being next to that valve in the [[US Divers]] product catalog. Valves without the reserve lever are called "K valves" for the same reason; being the next item in the catalog they were denoted by the letter K. Modern divers using "J valves" dive with the reserve valve in the open position and depend on a contents gauge or computer to monitor gas supply. ==First stage== The first stage of the regulator is usually designed to release the gas at a constant rate from the cylinder despite the pressure in the cylinder becoming less as the gas in the cylinder is used. The first stage takes gas from the [[diving cylinder]] at pressures of 200 - 300 bar (3000 - 4500 psi) and reduces its pressure to 10 bar (150 psi) higher than ambient pressure in the medium pressure hoses. ===Types=== The mechanism inside the first stage can be of the diaphragm type or the piston type. Both types can be balanced or unbalanced. A diaphragm first stage may be over-balanced as well. The performance of unbalanced regulators changes as the cylinder pressure falls, usually becoming slightly harder breathing. A balanced regulator keeps about the same ease of breathing at all depths and pressures. Over-balanced regulators provide more gas than the diver requires. [[Image:Diving regulator piston.PNG|right|350px|thumb|Diagram of the internal components of a piston-type first stage]] ====Piston type==== Piston-type first stages are easier to make and have a simpler design than the diaphragm type. This may help to improve reliability. They need more careful maintenance because some of the internal moving parts are exposed to water and contaminants in the water. With the piston-type first stage, the piston is rigid and acts directly on the seat of the valve. When the pressure in the medium pressure drops because the diver has used gas from a second stage valve, the piston lifts off the valve seat and slides towards the medium pressure chamber. This brings high pressure gas into the medium pressure chamber until the pressure in the chamber has risen enough to push the piston back onto the seat and close the valve. [[Image:Diving regulator diaphragm.PNG|right|350px|thumb|Diagram of the internal components of a diaphragm-type first stage]] ====Diaphragm type==== Diaphragm-type first stages are more complex and have more components than the piston type. They have an environmentally sealed design, and are thus particularly suited to cold water divers and those working in water containing a high degree of suspended particles, silt, or other contaminating materials. The [[Diaphragm (mechanical device)|diaphragm]] is a flexible cover to the medium-pressure chamber. When the diver consumes gas from a medium-pressure second stage, the pressure falls in the medium-pressure chamber and the diaphragm collapses inwards pushing against the valve lifter. This opens the valve letting high-pressure gas pass the valve seat into the medium-pressure chamber. When the pressure in the medium-pressure chambers rises, the diaphragm inflates outwards reducing the force on the valve lifter, letting the spring behind the valve close it. ===Risk of the regulator becoming blocked with ice=== As gas leaves the cylinder it decreases in pressure in the first stage, becoming very cold due to [[Adiabatic process|adiabatic expansion]]. Where the water temperature is less than 5°C any water inside the regulator may freeze, preventing the valve closing, causing a free-flow that can empty a full cylinder within a minute or two. Generally the water that freezes is in the ambient pressure chamber around a spring that keeps the valve open and not in moisture in the dry breathing gas from the cylinder. The modern trend of using more plastics, instead of metals, within the regulators encourages freezing because it insulates the inside of a cold regulator from the warmer surrounding water. Environmental sealing of the ambient pressure chamber and [[teflon]] coatings around springs are used to reduce the risk of freezing inside the regulator. ==Types of last stage== ===Not present=== If there is only one stage, and that stage is constant flow, the gas must be turned on and off at the cylinder. ===Manually operated valve=== The diver uses a button or lever or knob to blow gas or air into a device, such as [[buoyancy compensator]]s, [[drysuit]]s, and many [[rebreather]]s. This type of valve is connected to the first stage with a medium pressure hose commonly called a "direct feed". (The valves on [[blowtorch]]es are this type also.) ===Demand valve=== A demand valve detects when the diver starts inhaling and supplies the diver with a breath of gas at ambient pressure. The demand valve was [[Timeline of underwater technology#1865|invented in 1865]] in France, and forgotten in the next few years, and was not invented again until the late 1930s. The demand valve has a chamber, which in normal use contains breathing gas at ambient pressure. A valve which supplies medium pressure gas can vent into the chamber. Either a [[mouthpiece (scuba)|mouthpiece]] or a [[fullface mask]] is connected to the chamber, for the diver to breathe from. On one side of the chamber is a flexible [[diaphragm (mechanics)|diaphragm]] to control the operation of the valve. When the diver tries to breathe in, the inhalation lowers the pressure inside the chamber, which moves the diaphragm inwards operating a system of levers. This operates against the closing spring and lifts the valve off its seat, opening the valve and releasing gas into the chamber. The medium pressure gas, at about 10 bar/140 psi over ambient pressure, expands, reducing its pressure to ambient pressure, blowing out any water in the chamber and supplying the diver with gas to breathe. When the chamber is full and the lowering of pressure has been reversed, the diaphragm expands outwards to its normal position to close the medium pressure valve when the diver stops breathing in. When the diver exhales, one-way valves, made from a flexible and air-tight material, flex outwards under the pressure of the exhalation allowing gas to escape from the chamber. They close making a seal when the exhalation stops and the pressure inside the chamber reduces to ambient pressure. The diaphragm is protected by being covered by a second chamber, which the outside water can enter freely through large holes or slits. Some passive semi-closed circuit [[rebreather]]s use a form of demand valve, which senses the volume of the loop and injects more gas when the volume falls below a certain level. Most modern demand valves use a downstream rather than an upstream valve mechanism. In a downstream valve, the moving part of the valve opens in the downstream direction and is kept closed by a spring. In an upstream valve, the moving part works against the pressure and opens in an upstream direction. If the first stage jams open and the medium pressure system over-pressurises, the second stage downstream valve opens automatically resulting in a "freeflow". With an upstream valve, the result of over-pressurisation may be a ruptured hose or the failure of another second stage valve such as one that inflates a buoyancy device. ===Pressure relief valve=== A demand valve serves as a [[fail safe]] for over-pressurisation: if a first stage with a demand valve malfunctions and jams in the open position, the demand valve will be over-pressurised and will "free flow". Although it presents the diver with an imminent "out of air" crisis, this failure mode lets gas escape directly into the water without inflating buoyancy devices. The effect of unintentional inflation might be to carry the diver quickly to the surface causing the various [[Diving hazards and precautions#On ascent|injuries that can result from an over-fast ascent]]. There are circumstances where regulators are connected to inflatable equipment such as a [[rebreather]]'s breathing bag, a [[buoyancy compensator]] or a [[drysuit]] but without the need for demand valves. Examples of this are [[argon]] suit inflation sets, and "off board" or secondary diluent cylinders for closed-circuit [[rebreather]]s. When no demand valve is connected to a regulator, it should be equipped with a ''pressure relief valve'' so that over-pressurisation does not inflate any buoyancy devices connected to the regulator. ===Valve operated by a solenoid=== Fully closed circuit, electronic [[rebreather]]s have electronically controlled valves to inject fresh oxygen into the loop. The valve is opened with a [[solenoid]] in response to falling oxygen [[partial pressure]] detected by the [[electro-galvanic fuel cell]]s that monitor the loop. These valves are connected to the first stage with a direct feed. See [[Rebreather#Fully closed circuit rebreather]]. ==Arrangements of the assembly of valves== Often one first stage supplies in parallel two or more second stages of various types. Each of these second stages should be looked for below according to its type. Often a branch tube goes off without going through any pressure-reducing valve stages, to a [[pressure gauge]]. =Types of regulator= ==Constant flow== In constant-flow regulators the first stage is constant flow, and the second stage is a plain on/off valve. (In a [[blowtorch]] the first stage is fastened to the cylinder and the second stage is on the torch head.) They are the earliest type of breathing set regulator. They are used now in many [[rebreather]]s. The only control the diver has is to open or close the second stage. Constant flow valves in an open-circuit breathing set consume gas less economically than demand valve regulators because gas flows even when it is not needed. [[Image:Nemrod 2hose regulator.jpg|thumb|[[Nemrod]] Double-hose regulator made in the 1980s. It has one low-pressure port, which feeds the left (inhalation) hose. Its [[mouthpiece (scuba)|mouthpiece]] can be strapped in.]] In some [[rebreather]]s, e.g. the [[Siebe Gorman Salvus]], the oxygen cylinder has two first stages in parallel. One is constant flow; the other is a plain on-off valve called a [[Bypass (valve)|bypass]]; both feed into the same exit pipe which feeds the [[breathing bag]]. 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. With active semi-closed circuit rebreathers, the diver installs one of a number of different sized orifices in the valve before the dive. For safety reasons these should be chosen to provide more gas than the diver needs, to avoid [[Hypoxia (medical)|hypoxia]]. Before 1939, diving and industrial open-circuit breathing sets with constant-flow regulators were designed and made, but did not get into general use due to excessively short dive duration for its weight. Design complications resulted from the need to put the second-stage on/off valve where it could be easily operated by the diver. Examples were:- *"Ohgushi's Peerless Respirator". The valve was operated by the diver's teeth. *Commandant le Prieur's breathing sets: see [[Timeline of underwater technology]]. They were used for some [[sport diving]] on the [[French Riviera]]. [[Image:Aqualung old type.jpg|thumb|Old-type "twin-hose" Cousteau-type aqualung]] ==Twin-hose== The "twin", "double" or "two" hose type of scuba demand valve was the first in general use. <ref>http://www.vintagescubasupply.com/regseuro.html</ref> It has two (or occasionally one or three) stages in series in a large circular valve assembly mounted on top of the cylinder. The last (or only) stage is the demand valve. In Europe and the USA, as officially made, regulators were always fastened to the cylinder with an [[A-clamp]]. This type of regulator has two wide corrugated breathing tubes. The second tube was for exhalation; it was not for [[rebreather|rebreathing]] but to keep the air inside the breathing tube at the same pressure as the water outside the regulator diaphragm. This second breathing tube returns the exhaled air to the regulator on the wet side of the diaphragm, where it is released through a [[duck]]'s-beak-shaped rubber one-way valve, and comes out of the holes in the wet-side cover. Nearly always in the [[mouthpiece (scuba)|mouthpiece]] assembly there are one-way valves to stop air or water going from the mouthpiece into the inhaling tube or from the exhaling tube into the mouthpiece. In [[Jacques-Yves Cousteau|Cousteau]]'s first [[aqua-lung|aqualung]] as first made, there was no second tube and the exhaled breath exited to the outside through a one-way valve at the [[mouthpiece (scuba)|mouthpiece]]. It worked out of water, but when he tested the aqualung in the river [[Marne River|Marne]] air escaped from the regulator before it could be breathed when the mouthpiece was above the regulator. After that, he had the second breathing tube fitted. Even with both tubes fitted, raising the mouthpiece above the regulator increases the flow of gas and lowering the mouthpiece increases breathing resistance. As a result, many aqualung divers, when they were [[snorkeling]] on the surface to save air while reaching the dive site, put the loop of hoses under an arm to avoid the mouthpiece floating up causing free flow. Divers had to carry more weight underwater to compensate for the buoyancy of the air in the hoses. An advantage with this type of regulator is that the bubbles leave the regulator behind the diver's head, increasing visibility, and not interfering with [[underwater photography]]. They have been superseded by the single hose regulator and became obsolete for most diving in the 1980s. The original Cousteau twin-hose diving regulators could deliver about 140 [[litre]]s of air per minute, and that was officially thought to be adequate; but divers sometimes needed a faster rate, and had to learn not to "beat the lung", i.e. to try to breathe faster than the regulator could supply. Between 1948 and 1952 [[Ted Eldred]] designed his [[Porpoise (make of scuba gear)|Porpoise]] air scuba to supply 300 litres/minute if the diver need to breathe that fast, and that soon became British and Australian [[naval]] standard. Some modern twin-hose regulators have one or more low-pressure ports that branch off between the two valve stages, as ''direct feeds'', as described under [[#Two stage, single hose]] below. Someone made a twin-hose type regulator where the energy released as the air expands from cylinder pressure to the surrounding pressure as the diver breathes in, is not thrown away but used to power a [[propeller]]. 'The twin-hose setup with a [[mouthpiece (scuba)|mouthpiece]] or [[fullface mask]] has reappeared in modern [[rebreather]]s, but as part of the breathing loop, not as part of a regulator.' [[Image:Aqua lung.JPG|thumbnail|150px|A "single-hose" aqualung with the first stage on top of the cylinder and the second stage demand valve on the left hand hose]] ==Twin-hose, home-made== In 1956 and for some years afterwards in Britain, factory-made aqualungs were very expensive, and many aqualungs of this type were [[Timeline of underwater technology#1965|made by sport divers]] in diving clubs' workshops, using miscellaneous industrial and war-surplus parts. One necessary raw material was a [[Calor Gas]] bottled [[butane]] gas regulator, whose 1950s version was like an aqualung regulator's second stage but operated constant-flow because its diaphragm was spring-loaded; conversion included changing the spring and making several big holes in the wet-side casing. The cylinder was often an ex-[[Royal Air Force|RAF]] pilot's oxygen cylinder; some of these cylinders were called [[tadpole]]s from their shape. In least one version of Russian twin-hose aqualung, the regulator did not have an [[A-clamp]] but screwed into a large socket on the cylinder [[manifold (disambiguation)|manifold]]; that manifold was thin, and meandered somewhat. It had two cylinders and a pressure gauge. There is suspicion that those Russian aqualungs started as a factory-made improved descendant of an aqualung home-made by British sport divers and obtained unofficially by a Russian and taken to Russia. ==Two stage, single hose== Most modern scuba regulators are of this type. Its main components are: a ''first stage'', from which one or more ''medium pressure'' hoses run to various equipment listed below. The first make of this sort of scuba was the [[Porpoise (make of scuba gear)|Porpoise]] which was made in [[Australia]]. At the same time in France, The Cristal Explorer (single hose) by Bronnec & Gauthier. * [http://sdhr.fr.nf You can see The Cristal and more here] ==Unusual designs== ===Twin-hose without visible regulator valve (fictional)=== This type is mentioned here because it is very familiar in [[comic]]s and other drawings, as a wrongly-drawn twin-hose aqualung regulator, with one wide hose coming out of each cylinder top with no apparent regulator valve, much more often than a correctly-drawn twin-hose regulator: see [[Frogman#Drawing and artwork]]. It would not work in the real world. ===Demone regulator=== This type was designed by Robert J. [[Dempster]] and made at his factory in [[Illinois]], USA, from 1961 to 1965. It operates like a single-hose regulator. The second-stage looks like the mouthpiece of a twin-hose regulator, but with a small diaphragm on the front. The second-stage valve is inside one end of the mouthpiece tube. The exhaled air goes into a twin-hose-type exhalant tube which surrounds the intermediate-pressure hose and blows out at its end about 60% of the way back to the first-stage, to keep the bubbles away from the diver's face. Near the mouthpiece is a one-way valve to let outside water into the exhalant hose to avoid air run-away if the diaphragm (at the mouth) is below the open end of the exhalant hose. Many Demone regulators have two intermediate-pressure tubes and two exhalant hoses and two second-stages, one assembly on each side of the diver's head, causing a superficial resemblance to the fictional "Twin-hose without visible regulator valve".<ref>[[Historical Diving Society|Historical Diving Times]], #42, Summer 2007, pp5-7</ref> ===Practical Mechanics design=== This design was described in [[Practical Mechanics]] magazine in January 1955, as a home-made aqualung with a first-stage on the cylinder top leading through an intermediate-pressure hose to a large round second-stage (a converted [[Calor Gas]] regulator) on the diver's chest connected to the diver's mouthpiece by a twin-hose loop. [http://www.vintagedoublehose.com/downloads/MakinganAqualung2.pdf] ==First stage valve== The '''first stage''' has a high-pressure "port" for the high-pressure hose to the [[pressure gauge]]. It has a number of "ports" for low-pressure hoses to carry gas to other components, which serve as second-stage valves of various sorts. All unused ports must be blanked off. With regulators that are used as breathing sources, at least one low-pressure hose connects to a ''demand valve''. Some low-pressure hoses connect to the [[diving suit]] inflation valve and the [[buoyancy compensator]] inflation valves: these low-pressure hoses are called ''direct feeds''. ==Second stage valve== A second stage valve can be:- ===Direct feed or power inflator=== [[Image:Diving regulator direct feed.jpg|thumb|right|A drysuit direct feed a.k.a. a power inflator]] A connection to inflate a [[buoyancy compensator]] or a [[drysuit]], is manually operated by a button or lever or knob. ===Demand valve=== [[Image:diving regulator demand valve.JPG|thumb|right|A pair of demand valves]] This type of second stage is called ''demand valve'' or ''DV''. It is fed by a ''medium pressure hose'' from the first-stage. It works as described in the ''[[#Types of last stage]]'' section above. When the diver breathes out, the air goes to the dry side of the diaphragm, and is released to the outside through (usually two) one-way valves. It has a ''purge button'', which the diver can press to depress the diaphragm to make gas flow to blow water out of the [[mouthpiece (scuba)|mouthpiece]] (or for other purposes such as filling a [[lifting bag]]). ====Octopus==== Sometimes (nowadays nearly always) a single-hose regulator has more than one demand valve (= DV). If the extra DV is simply a spare DV for use by the diver's [[buddy system|buddy]] it is usually called an '''octopus'''. The medium pressure hose on the octopus is usually longer than the medium pressure hose on the DV that the diver uses. ====Combined DV and BC inflator==== [[Image:Diving regulator demand valve and bcd inflate.JPG|thumb|right|A combined diving regulator demand valve and BC inflation valve]] The demand valve could be a hybrid DV and [[buoyancy compensator]] inflation valve. Both types are sometimes called '''alternate air sources''', and more confusingly a DV on a regulator connected to a separate independent [[diving cylinder]] would also be called an "alternate air source". ====Full face mask==== [[Image:Patent spec of Le Prieur regulator.gif|thumb|right|diagram of the 1946 version of the Le Prieur breathing set]] There have been at least two cases of a single-hose-type demand regulator last stage built into a circular [[fullface mask]] so that the mask's big circular front window plus the flexible rubber seal joining it to its frame, was a very big and thus very sensitive regulator diaphragm:- *A version of the Le Prieur breathing set. [[Yves Le Prieur]] patented it in 1946 and the [[patent]] was granted on [[10 February]] [[1947]]. *[[Captain Trevor Hampton]] invented independently a similar regulator-mask in the 1950s and submitted it for patent, but the [[Royal Navy]] requisitioned the patent, but found no use for it and eventually released it, but by then the market had moved on and it was too late to make this regulator-mask in bulk for sale. ====Dive/surface valve or bailout valve==== A Dive/surface valve (DSV) or bailout valve (BOV) is a device in the [[mouthpiece (scuba)|mouthpiece]] on the loop of a [[rebreather]] 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. [http://www.divenet.com/divematics/mouthpiece/] = Performance of regulators = {{main|breathing performance of regulators}} In Europe, '''[[European Norm|EN]]250:2000''' defines the minimum requirements for [[breathing performance of regulators]]. In the United States Military, scuba regulators must adhere to performance specifications as outlined by the Mil-R-24169B which was based on equipment performance until recently.<ref>{{cite journal |last=Middleton |first=JR |title=Evaluation of Commercially Available Open Circuit Scuba Regulators |journal=US Naval Experimental Diving Unit Technical Report |volume=NEDU-2-80 |date=[[1980]] |url=http://archive.rubicon-foundation.org/3375 |accessdate=2008-06-12 }}</ref><ref>{{cite journal |last=Morson |first=PD |title=Evaluation of Commercially Available Open Circuit Scuba Regulators |journal=US Naval Experimental Diving Unit Technical Report |volume=NEDU-8-87 |date=[[1987]] |url=http://archive.rubicon-foundation.org/4259 |accessdate=2008-06-12 }}</ref><ref>{{cite journal |last=Warkander |first=DE |title=Comprehensive Performance Limits for Divers' Underwater Breathing Gear: Consequences of Adopting Diver-Focused Limits |journal=US Naval Experimental Diving Unit Technical Report |volume=NEDU-TR-07-02 |date=[[2007]] |url=http://archive.rubicon-foundation.org/4984 |accessdate=2008-06-12 }}</ref> Various breathing machines have been developed and used for assessment of breathing apparatus performance.<ref>{{cite journal |last=Reimers |first=SD |title=Performance Characteristics and Basic Design Features of a Breathing Machine for Use to Depths of up to 3000 Feet of Sea Water |journal=US Naval Experimental Diving Unit Technical Report |volume=NEDU-20-73 |date=[[1973]] |url=http://archive.rubicon-foundation.org/4100 |accessdate=2008-06-12 }}</ref> [[ANSTI]] has developed a testing machine that measures the inhalation and exhalation effort in using a regulator; publishing results<ref>{{cite web |url=http://www.scubadiving.com/gear/regulators/bonus_2007_reg_test/ansti_machine |title=The ANSTI Machine: Evaluating A Regulator's Breathing Characteristics - Scuba Diving Magazine}}</ref> of the performance of regulators in the ANSTI test machine has resulted in big performance improvements. ==Manufacturers== *Air Liquide: [http://www.apeks.co.uk/ Apeks] and [http://www.aqualung.com/ Aqua Lung] *[http://www.apollo-sports.co.jp/ Apollo Sports] *[http://www.atomicaquatics.com/ Atomic Aquatics] *[http://www.beuchat.fr/ Beuchat] *[http://www.cressi.it/ Cressi Sub] * HTM Sports: [http://www.divedacor.com Dacor] and [http://www.mares.com/ Mares] *[http://www.poseidon.se/ Poseidon] *ROMI Enterprises: [http://www.diveaeris.com/ Aeris] and [http://www.oceanicworldwide.com/ Oceanic] *[http://www.oceandivers.com.tw Ocean Divers Supply] *[http://www.scubapro.com/ ScubaPro] *[http://www.tusa.net/ Tusa] *[http://www.zeagle.com/ Zeagle] ==Value Added Reseller== *[http://www.diverite.com/ Dive Rite] *[http://www.coltrisub.it/ Coltri] *[http://www.genesisscuba.com/ Genesis] *[http://www.omsdive.com/ OMS] *[http://www.seacsub.it/ Seacsub] *[http://www.sherwoodscuba.com/ Sherwood] *[http://www.tigullio52.com/ Tigullio] *[http://www.xsscuba.com XS Scuba] ** (see [[Original equipment manufacturer]]) =References= <references/> == Headline text == =External links= * [http://sdhr.fr.nf Website about Regulator's History, vintage single and Twin hoses regulators] * [http://sdhr.fr.nf/forum/ New FORUM October 2007! about Vintage Regulators - Join SDHR Team now!] * [http://www.scubadiving.com/gear/regulators Regulators reviews] by ''Scuba Diving'' magazine. * [http://www.divernetxtra.com/gear/gtests.shtml Regulators reviews I] by ''DIVERNET'' magazine. * [http://www.divernet.com/cgi-bin/articles.pl?section=2019 Regulators reviews II] by ''DIVERNET'' magazine. * [http://adventure.howstuffworks.com/scuba2.htm How Scuba Works: Scuba Breathing Apparatus] [[Category:Diving equipment]] [[Category:Underwater diving]] [[de:Lungenautomat]] [[fr:Détendeur]] [[no:Pusteventil]] [[pl:Automat oddechowy]] [[ru:Регулятор (дайвинг)]] [[sv:Regulatorpaket]] [[it:Erogatore]]