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Deep diving has different meanings depending on the context. Even in recreational diving the meaning may vary: In recreational diving, a depth below about , where nitrogen narcosis becomes a significant hazard for some divers, may be considered a "deep dive". For some recreational diving agencies, ''Deep diving'', or ''Deep diver'' may be a certification awarded to divers that have been trained to dive to a specified depth range, generally deeper than . However, the Professional Association of Diving Instructors (PADI) defines anything from to as a "deep dive" in the context of recreational diving (other diving organisations vary), and considers ''deep diving'' a form of technical diving. In technical diving, a depth below about where hypoxic breathing gas becomes necessary to avoid oxygen toxicity may be considered a "deep dive". In professional diving, a depth that requires special equipment, procedures, or advanced training may be considered a ''deep dive''. Deep diving can mean something else in the commercial diving field. For instance early experiments carried out by Comex S.A. (Compagnie maritime d'expertises) using hydrox and trimix attained far greater depths than any recreational technical diving. One example being the Comex Janus IV open-sea dive to in 1977.〔(Hydra 8: Pre-commercial Hydrogen Diving Project )〕 The open-sea diving depth record was achieved in 1988 by a team of Comex divers who performed pipe line connection exercises at a depth of in the Mediterranean Sea as part of the Hydra 8 programme. These divers needed to breathe special gas mixtures because they were exposed to very high ambient pressure (more than 50 times atmospheric pressure). An atmospheric diving suit allows very deep dives of up to . These suits are capable of withstanding the pressure at great depth permitting the diver to remain at normal atmospheric pressure. This eliminates the problems associated with breathing high pressure gases. ==Depth ranges in underwater diving== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Deep diving」の詳細全文を読む スポンサード リンク
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