Editing Scuba set (section)

==History==
{{see also|History of scuba diving|Timeline of diving technology}}
[[Image:Dykeri, fig 6, Nordisk familjebok.png|thumb|left|upright=0.7|The Rouquayrol-Denayrouze apparatus was the first regulator to be [[Mass production|mass-produced]] (from 1865 to 1965). In this picture the air reservoir presents its surface-supplied configuration.]]
[[File:Henry Albert Fleuss.jpg|thumb|[[Henry Fleuss]] (1851–1932) improved the [[Diving rebreather|rebreather]] technology.]]
[[Image:Aqualung (PSF).png|thumb|upright=0.7|left|[[Aqua-lung|Aqualung]] scuba set.
{{unbulleted list |
|1. Breathing hose
|2. Mouthpiece
|3. Cylinder valve and regulator
|4. Harness
|5. Backplate
|6. Cylinder
}}
]]
By the turn of the twentieth century, two basic architectures for underwater breathing apparatus had been pioneered; open-circuit surface supplied equipment where the diver's exhaled gas is vented directly into the water, and closed-circuit breathing apparatus where the diver's carbon dioxide is filtered from unused oxygen, which is then recirculated. Closed circuit equipment was more easily adapted to scuba in the absence of reliable, portable, and economical high pressure gas storage vessels. By the mid twentieth century, high pressure cylinders were available and two systems for scuba had emerged: [[open-circuit scuba]] where the diver's exhaled breath is vented directly into the water, and [[Diving rebreather|closed-circuit scuba]] where the [[carbon dioxide]] is removed from the diver's exhaled breath which has oxygen added and is recirculated. Oxygen rebreathers are severely depth limited due to oxygen toxicity risk, which increases with depth, and the available systems for mixed gas rebreathers were fairly bulky and designed for use with diving helmets.<ref name="Draegerwerk1899" /> The first commercially practical scuba rebreather was designed and built by the diving engineer [[Henry Fleuss]] in 1878, while working for [[Siebe Gorman]] in London.<ref name=davis1955 /> His [[self contained breathing apparatus]] consisted of a rubber mask connected to a breathing bag, with an estimated 50–60% oxygen supplied from a copper tank and carbon dioxide scrubbed by passing it through a bundle of rope yarn soaked in a solution of caustic potash, the system giving a dive duration of up to about three hours. This apparatus had no way of measuring the gas composition during use.<ref name=davis1955/><ref name="Quick 1970" /> During the 1930s and all through [[World War II]], the British, Italians and Germans developed and extensively used oxygen rebreathers to equip the first [[Frogman|frogmen]]. The British adapted the Davis Submerged Escape Apparatus and the Germans adapted the [[Drägerwerk|Dräger]] submarine escape rebreathers, for their frogmen during the war.<ref name="Diving Heritage" /> In the U.S. [[Major (United States)|Major]] [[Christian J. Lambertsen]] invented an underwater free-swimming [[oxygen rebreather]] in 1939, which was accepted by the [[Office of Strategic Services]].<ref name="Shapiro" /> In 1952 he patented a modification of his apparatus, this time named SCUBA, (an acronym for "self-contained underwater breathing apparatus"),<ref name=patent /><ref name="Brubakk 2003"/><ref name="Vann 2004" /><ref name="Butler 2004" /> which became the generic English word for autonomous  breathing equipment for diving, and later for the activity using the equipment.<ref name="oxford" /> After World War II, military frogmen continued to use rebreathers since they do not make bubbles which would give away the presence of the divers. The high percentage of oxygen used by these early rebreather systems limited the depth at which they could be used due to the risk of convulsions caused by acute [[oxygen toxicity]].<ref name="US Navy Diving Manual 2006" />

Although a working demand regulator system had been invented in 1864 by [[Auguste Denayrouze]] and [[Benoît Rouquayrol]],<ref name="Denayrouze" /> the first open-circuit scuba system developed in 1925 by [[Yves Le Prieur]] in France was a manually adjusted free-flow system with a low endurance, which limited the practical usefulness of the system.<ref name="Le Prieur" /> In 1942, during the German occupation of France, [[Jacques-Yves Cousteau]] and [[Émile Gagnan]] designed the first successful and safe open-circuit scuba, known as the [[Aqua-Lung]]. Their system combined an improved demand regulator with high-pressure air tanks.<ref name="Cousteau 1953" /> This was patented in 1945. To sell his regulator in English-speaking countries Cousteau registered the Aqua-Lung trademark, which was first licensed to the [[U.S. Divers]] company,<ref name=Grima /> and in 1948 to Siebe Gorman of England,<ref name=Tadpole /> Siebe Gorman was allowed to sell in Commonwealth countries, but had difficulty in meeting the demand and the U.S. patent prevented others from making the product. The patent was circumvented by Ted Eldred of [[Melbourne]], Australia, who developed the single-hose open-circuit scuba system, which separates the first stage and demand valve of the pressure regulator by a low-pressure hose, puts the demand valve at the diver's mouth, and releases exhaled gas through the demand valve casing. Eldred sold the first [[Porpoise (make of scuba gear)|Porpoise]] Model CA single hose scuba early in 1952.<ref name="Byron 2014" />

Early scuba sets were usually provided with a plain harness of shoulder straps and waist belt. The waist belt buckles were usually quick-release, and shoulder straps sometimes had adjustable or quick release buckles. Many harnesses did not have a backplate, and the cylinders rested directly against the diver's back.<ref name="Basic Scuba" /> Early scuba divers dived without a buoyancy aid.<ref name="Silent World b" /> In an emergency they had to jettison their weights. In the 1960s [[adjustable buoyancy life jacket]]s (ABLJ) became available, which can be used to compensate for loss of buoyancy at depth due to compression of the [[neoprene]] [[wetsuit]] and as a [[lifejacket]] that will hold an unconscious diver face-upwards at the surface, and that can be quickly inflated. The first versions were inflated from a small disposable carbon dioxide cylinder, later with a small direct coupled air cylinder. A low-pressure feed from the regulator first-stage to an inflation/deflation valve unit an oral inflation valve and a dump valve lets the volume of the ABLJ be controlled as a buoyancy aid. In 1971 the [[stabilizer jacket]] was introduced by [[ScubaPro]]. This class of buoyancy aid is known as a buoyancy control device or buoyancy compensator.<ref name="Hanauer 1994" /><ref name="Krestovnikov and Halls 2008" />

[[File:Sidemount 032 Photo by Pete Nawrocky.jpg|thumb|Sidemount diver pushing a cylinder in front]]
A backplate and wing is an alternative configuration of scuba harness with a buoyancy compensation bladder known as a "wing" mounted behind the diver, sandwiched between the backplate and the cylinder or cylinders. Unlike stabilizer jackets, the backplate and wing is a modular system, in that it consists of separable components. This arrangement became popular with cave divers making long or deep dives, who needed to carry several extra cylinders, as it clears the front and sides of the diver for other equipment to be attached in the region where it is easily accessible. This additional equipment is usually suspended from the harness or carried in pockets on the exposure suit.<ref name="Jablonski 2006" /><ref name="Mount 2008b" /> Sidemount is a scuba diving equipment configuration which has basic [[scuba sets]], each comprising a single cylinder with a dedicated regulator and pressure gauge, mounted alongside the diver, clipped to the harness below the shoulders and along the hips, instead of on the back of the diver. It originated as a configuration for advanced [[cave diving]], as it facilitates penetration of tight sections of cave as, sets can be easily removed and remounted when necessary. The configuration allows easy access to cylinder valves, and provides easy and reliable gas redundancy.  These benefits for operating in confined spaces were also recognized by divers who made [[wreck diving]] penetrations. Sidemount diving has grown in popularity within the [[technical diving]] community for general [[decompression diving]],<ref name="diverwire" /> and has become a popular specialty for recreational diving.<ref name="Alert" /><ref name="divernet" /><ref name="x-ray1" />

[[File:TechDiving NOAA.jpg|thumb|Technical diver during a decompression stop]]
Technical diving is recreational scuba diving that exceeds the generally accepted recreational limits, and may expose the diver to hazards beyond those normally associated with recreational diving, and to greater risks of serious injury or death. These risks may be reduced by appropriate skills, knowledge and experience, and by using suitable equipment and procedures. The concept and term are both relatively recent advents, although divers had already been engaging in what is now commonly referred to as technical diving for decades. One reasonably widely held definition is that any dive in which at some point of the planned profile it is not physically possible or physiologically acceptable to make a direct and uninterrupted vertical ascent to surface air is a technical dive.<ref name="Menduno 2012" /> The equipment often involves breathing gases other than air or standard [[nitrox]] mixtures, multiple gas sources, and different equipment configurations.<ref name=Richardson/> Over time, some equipment and techniques developed for technical diving have become more widely accepted for recreational diving.<ref name="Menduno 2012" />

The challenges of deeper dives and longer penetrations and the large amounts of breathing gas necessary for these dive profiles and ready availability of oxygen sensing cells beginning in the late 1980s led to a resurgence of interest in rebreather diving. By accurately measuring the partial pressure of oxygen, it became possible to maintain and accurately monitor a breathable gas mixture in the loop at any depth.<ref name="Menduno 2012" /> In the mid 1990s semi-closed circuit rebreathers became available for the recreational scuba market, followed by closed circuit rebreathers around the turn of the millennium.<ref name="Mitchell and Doolette 2013" /> Rebreathers are currently (2018) manufactured for the military, technical and recreational scuba markets.<ref name="Menduno 2012" />