Scuba diving Guide, Meaning , Facts, Information and Description
SCUBA is an acronym for Self Contained Underwater Breathing Apparatus. (These initials likely originated in the US Navy to refer to US commando frogman's rebreathers.) As with radar, the acronym has become so familiar that capitalisation is often omitted. In short, scuba diving is an underwater activity practiced with the help of equipment worn by the diver, which provides a supply of breathing gas allowing the diver to remain underwater for long periods.There are two types of SCUBA equipment:
- the Aqua-Lung - a system consisting of a tank or diving cylinder containing a high pressure breathing gas connected to diving regulator that supplies the diver with that gas at a pressure suitable for breathing at the depth of the diver. This type of SCUBA equipment is known as 'open circuit' because exhaled gas is lost to the environment.
- the Rebreather - supplies the diver with breathing gas from a diving cylinder and a diving regulator but consists of other mechanisms that safely recycle the exhaled gas. This type of SCUBA equipment is known as 'closed circuit'. Its economic use of gas allows dives of much longer endurance than is possible with open circuit equipment.
- free-diving - swimming underwater on a single breath of air.
- snorkeling - a form of free-diving where the diver's mouth and nose can remain underwater when breathing, because the diver is able to breathe at the surface through a short tube known as a snorkel.
- surface supplied diving - mainly used in professional diving for long or deep dives where an umbilical line connects the diver with the surface providing breathing gas, warm water to heat diving suits and voice communications.
- SCBA Self Contained Breathing Apparatus - positive pressure face masks and gas cylinders used by rescue and fire services
- Rebreather technology is also used in mine rescue equipment and space suits
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2 Variants of open-circuit scuba 3 Related topics 4 External links |
See also Timeline of underwater technology.
The first known mention of air tanks is in Italy, 15th century: Leonardo da Vinci affirmed in his Atlantic Codex (Biblioteca Ambrosiana, Milan) that systems were used at that time to artificially breathe under water, but he did not explain them in detail due to what he described as "bad human nature", that would have taken advantage of this technique to sink ships and even commit murders. Some drawings, however, showed different kinds of snorkels and an air tank (to be carried on the breast) that presumably should have no external connections. Other drawings showed a complete immersion kit, with a plunger suit which included a sort of mask with a box for air. The project was so detailed that it included a urine collector, too.
In 1829 Charles and John Deane of Whitstable in Kent in England designed the first air-pumped diving helmet. It is said that the idea started from a crude emergency rig-up of a fireman's water-pump (used as an air pump) and a knight-in-armour helmet used to try to rescue horses from a burning stable.
After Leonardo's studies, and those of Halley the astronomer, in 1837 Augustus Siebe developed standard diving dress, a sort of surface supplied diving apparatus.
Some time afterwards, the Frenchman Joseph Cabirol started making standard diving dress.
In 1865 Benoit Rouquayrol and Auguste Denayrouze designed a diving set with a backpack spherical air tank that supplied air through the first known demand regulator. The diver still walked on the seabed and did not swim. This set was called an aérophore. But pressure cylinders made with the technology of the time could only hold 30 atmospheres, and the diver had to be surface supplied; the tank was for bailout. The durations of 6 to 8 hours on a tankful without external supply recorded for the Rouquayrol set in the book "Twenty Thousand Leagues under the Seas" by Jules Verne, are wildly exaggerated fiction. Judging by Jules Verne's inaccurate attempts in the book at describing how the Rouquayrol set worked, how the demand regulator works was not generally known or had already been forgotten when he wrote the book, which was published in 1870.
In the late 19th century and after, industry could make high-pressure air and gas cylinders. That prompted a few inventors down the years to design open-circuit compressed air breathing sets, but they were all constant-flow, and the demand regulator did not come back until 1939.
In 1879 Henry Fluess invented the first closed circuit breathing device using stored oxygen and adsorption of carbon dioxide by a caustic soda or rebreather for the rescue of mineworkers who were trapped by water.
In 1906 the first decompression tables ("quote decompression method") were released.
In 1915 Sir Robert Davis invented an oxygen rebreather called the "Submarine Escape Apparatus" to escape from sunken submarines. It was the first rebreather to be made in quantity. After that, various sorts of industrial oxygen rebreathers were made down the years for use in unbreathable atmospheres on land.
In 1933 Yves Le Prieur invented a constant-flow open-circuit breathing set. It could allow a 20 minute stay at 7 meters and 15 minutes at 15 meters (these data appear however to be re-checked). These sets were used by the first known sport diving club, which started in 1935.
In the 1930's sport spearfishing became common in the Mediterranean, and spearfishers gradually developed the common sport diving mask and fins and snorkel, and Italian sport spearfishers started using oxygen rebreathers.
In 1939 the Frenchman Georges Commeinhes developed a two-cylinder open-circuit apparatus with demand regulator. The regulator was a big rectangular box between the cylinders. He offered this set to the French Navy, which could not continue developing uses for it because of WWII. In July 1943 he reached 53 meters (about 174 feet) using it off the coast of Marseille, But he died in 1944 in the liberation of Strasbourg in Alsace.
In 1941, during WWII, Italy used rebreathers were used for one of the best known and most spectacular war actions: Italian "Decima Mas" (elite navy corps at the orders of commander Junio Valerio Borghese) entered at nighttime the port of Alexandria in Egypt underwater. They used special underwater vehicles ("maiali" = pigs) and breathing apparatus, and were able to silently attach miness on the bottoms of the ships, that later were effectively sunk.
In 1943 Jacques Cousteau and Emile Gagnan invented an open-circuit diving breathing set, using a demand regulator which Gagnan modified from a demand regulator used to let a petrol-driven car run on a big bag of coal-gas carried on its roof during wartime shortages of petrol. This set was later named the Aqua-Lung. This word is correctly a tradename that goes with the Cousteau-Gagnan patent, but in Britain it has been commonly used as a generic and spelt "aqualung" since at least the 1950's, including in the BSAC's publications and training manuals, and describing scuba diving as "aqualunging". In October [1944]] Frédéric Dumas reached 62 meters (about 200 feet) with this set.
In 1953 the National Geographical Society Magazine published an article about Cousteau's underwater archaeology at Grand Congloué island near Marseilles, and in French-speaking countries a diving film called Épaves (= Shipwrecks) came out. That started a massive public demand for aqualungs and diving gear, and in France and America the diving gear makers started making them as fast as they could. But in Britain Siebe Gorman Ltd kept aqualungs expensive, and many British sport divers had to use home-made breathing sets and ex-armed forces or ex-industry rebreathers, and some became expert at home-making diving demand regulators from industrial parts. Finally Submarine Products Ltd in Hexham in Northumberland in England designed round the Cousteau-Gagnan patent and made sport diving breathing sets accessibly cheap.
In 1958 the television series Sea Hunt introduced SCUBA diving to the television audience.
In Italy, sport diving oxygen rebreathers continued to be made well into the 1960's.
Films have also popularized the sport. SCUBA diving is featured in films such as The Abyss (including as-yet-fictional deep-sea liquid-breathing sets), James Bond in Thunderball (using both sorts of open-circuit scuba) and Fantastic Voyage (using rebreathers).
Most modern open-circuit scuba have the first stage regulator (pressure reducer) on the cylinder pack, and the second stage at the mouthpiece, with a thin pressure hose between. This type is called "single hose". Many modern scuba sets have two second-stages, each on a hose; the spare second-stage is called an octopus.
There have been designs for a cryogenic open-circuit scuba, which has liquid-air tanks instead of cylinders. One type is the Russian Kriolang, which was copied from Jordan Klein's "Mako" cryogenic open-circuit diving set. This link shows pictures of a Kriolang that was made in 1974. Its diving duration is likely several hours. It would have to be filled immediately before use.
This is an Article on Scuba diving. Page Contains Information, Facts Details or Explanation Guide About Scuba diving History
Variants of open-circuit scuba
The early aqualungs had one or more (usually two) cylinders lengthwise on the back. The first and second stages of the regulator were in a large circular valve assembly mounted on top of the cylinder pack. It had two wide breathing tubes like on many modern rebreathers. The return tube was not for rebreathing but because the air exhaust exit had to be at the same level as the regulator's second stage's diaphragm to avoid pressure differences causing free-flow or resistance to breathing acording to the diver's attitude in the water. This type is called "twin hose". Scuba at this period did not have any sort of buoyancy aid ("wings" or BCD / stab-jacket), but a plain strap harness like on a rucksack or spray-tank-pack. Many did not have a backpack plate, but the cylinders were directly against the diver's back.Related topics
External links