Nitrox refers to any gas mixture composed of nitrogen and oxygen. This includes atmospheric air, which is approximately 78% nitrogen, 21% oxygen, and 1% other gases, primarily argon. In the usual application, underwater diving, nitrox is normally distinguished from air and handled differently. The most common use of nitrox mixtures containing oxygen in higher proportions than atmospheric air is in scuba diving, where the reduced partial pressure of nitrogen is advantageous in reducing nitrogen uptake in the body's tissues, thereby extending the practicable underwater dive time by reducing the decompression requirement, or reducing the risk of decompression sickness.
Trimix is a breathing gas consisting of oxygen, helium and nitrogen and is used in deep commercial diving, during the deep phase of dives carried out using technical diving techniques, and in advanced recreational diving.
Technical diving is scuba diving that exceeds the agency-specified limits of recreational diving for non-professional purposes. Technical diving may expose the diver to hazards beyond those normally associated with recreational diving, and to a greater risk of serious injury or death. Risk may be reduced via appropriate skills, knowledge, and experience. Risk can also be managed by using suitable equipment and procedures. The skills may be developed through specialized training and experience. The equipment involves breathing gases other than air or standard nitrox mixtures, and multiple gas sources.
A divemaster (DM) is a role that includes organising and leading recreational dives, particularly in a professional capacity, and is a qualification used in many parts of the world in recreational scuba diving for a diver who has supervisory responsibility for a group of divers and as a dive guide. As well as being a generic term, 'Divemaster' is the title of the first professional rating of many training agencies, such as PADI, SSI, SDI, NASE, except NAUI, which rates a NAUI Divemaster under a NAUI Instructor but above a NAUI Assistant Instructor. The divemaster certification is generally equivalent to the requirements of ISO 24801-3 Dive Leader.
Recreational diving or sport diving is diving for the purpose of leisure and enjoyment, usually when using scuba equipment. The term "recreational diving" may also be used in contradistinction to "technical diving", a more demanding aspect of recreational diving which requires more training and experience to develop the competence to reliably manage more complex equipment in the more hazardous conditions associated with the disciplines. Breath-hold diving for recreation also fits into the broader scope of the term, but this article covers the commonly used meaning of scuba diving for recreational purposes, where the diver is not constrained from making a direct near-vertical ascent to the surface at any point during the dive, and risk is considered low.
Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface breathing gas supply, and therefore has a limited but variable endurance. The name scuba is an anacronym for "Self-Contained Underwater Breathing Apparatus" and was coined by Christian J. Lambertsen in a patent submitted in 1952. Scuba divers carry their own source of breathing gas, usually compressed air, affording them greater independence and movement than surface-supplied divers, and more time underwater than free divers. Although the use of compressed air is common, a gas blend with a higher oxygen content, known as enriched air or nitrox, has become popular due to the reduced nitrogen intake during long or repetitive dives. Also, breathing gas diluted with helium may be used to reduce the effects of nitrogen narcosis during deeper dives.
Scuba Diving International (SDI) is a Scuba training and certification agency. It is the recreational arm of Technical Diving International, a technical diver training organization.
Technical Diving International (TDI) claims to be the largest technical diving certification agency in the world, and one of the first agencies to offer mixed gas and rebreather training. TDI specializes in more advanced Scuba diving techniques, particularly diving with rebreathers and use of breathing gases such as trimix and heliox.
American Nitrox Divers International was founded by Ed Betts and Dick Rutkowski in 1988.
The World Recreational Scuba Training Council (WRSTC) was founded in 1999 and is dedicated to creating minimum recreational diving training standards for the various scuba diving certification agencies across the world. The WRSTC restricts its membership to national or regional councils. These councils consist of individual training organizations who collectively represent at least 50% of the annual diver certifications in the member council's country or region. A national council is referred to as a RSTC.
Master Scuba Diver (MSD) is a scuba diving certification or recognition level offered by several North American diver training agencies, such as the National Association of Underwater Instructors (NAUI), the Professional Association of Diving Instructors (PADI), Scuba Diving International (SDI), and Scuba Schools International (SSI). Other agencies offer similar programs under other names, such as "Elite Diver". Each of these agencies touts their program at this level as the highest, non-leadership program.
The European Underwater Federation (EUF) is an umbrella organisation representing the interests of scuba diver training organisations operating in both the not for profit and for profit sectors within Europe.
Tom Mount was an American pioneering cave diver and technical diver.
Richard Rutkowski is a pioneer in the fields of hyperbaric medicine, diving medicine and diver training, especially in relation to the use of breathing gases.
Confédération Mondiale des Activités Subaquatiques (CMAS) is an international federation that represents underwater activities in underwater sport and underwater sciences, and oversees an international system of recreational snorkel and scuba diver training and recognition. It is also known by its English name, the World Underwater Federation, and its Spanish name, Confederación Mundial De Actividades Subacuáticas. Its foundation in Monaco during January 1959 makes it one of the world's oldest underwater diving organisations.
A Diving certification or C-card is a document recognizing that an individual or organization authorized to do so, "certifies" that the bearer has completed a course of training as required by the agency issuing the card. This is assumed to represent a defined level of skill and knowledge in underwater diving. Divers carry a qualification record or certification card which may be required to prove their qualifications when booking a dive trip, hiring scuba equipment, having diving cylinders filled, or in the case of professional divers, seeking employment.
Bret Clifton Gilliam was an American pioneering technical diver. He was most famous as co-founder of the certification agency Technical Diving International along with Mitch Skaggs, and as the one time holder of the world record for deep diving on air. He is also one of diving's most popular writers. Gilliam is the author or coauthor of 72 books, over 1500 feature magazine articles, and over 100 magazine cover photos. In his diving career he has logged over 19,000 dives(NOT VERIFIED) since 1959.
John Morgan Wells was a marine biologist, and physiologist involved in the development of decompression systems for deep diving, and the use of nitrox as a breathing gas for diving. He is known for developing the widely used NOAA Nitrox I and II mixtures and their decompression tables in the late 1970s, the deep diving mixture of oxygen, helium, and nitrogen known as NOAA Trimix I, for research in undersea habitats, where divers live and work under pressure for extended periods, and for training diving physicians and medical technicians in hyperbaric medicine.
The history of scuba diving is closely linked with the history of the equipment. 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 the exhaled breathing gas, which is then recirculated, and more gas added to replenish the oxygen content. 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 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. 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. 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. During the 1930s and all through World War II, the British, Italians and Germans developed and extensively used oxygen rebreathers to equip the first frogmen. In the U.S. Major Christian J. Lambertsen invented a free-swimming oxygen rebreather. In 1952 he patented a modification of his apparatus, this time named SCUBA, an acronym for "self-contained underwater breathing apparatus," which became the generic English word for autonomous breathing equipment for diving, and later for the activity using the equipment. 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.
