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Inert gas asphyxiation is a form of asphyxiation which results from breathing a physiologically inert gas in the absence of oxygen, or a low amount of oxygen,〔European Industrial Gases Association (2009), ''(Hazards of Inert Gases and Oxygen Depletion ), IGC Doc 44/09/E〕 rather than atmospheric air (which is largely composed of oxygen and nitrogen). Examples of physiologically inert gases, which have caused accidental or deliberate death by this mechanism, are argon, helium, nitrogen, and methane. The term "physiologically inert" is used to indicate a gas which has no toxic or anesthetic properties and does not act upon the heart or hemoglobin. Instead, the gas acts as a simple diluent to reduce oxygen concentration in inspired gas and blood to dangerously low levels, thereby eventually depriving all cells in the body of oxygen.〔 According to the U.S. Chemical Safety and Hazard Investigation Board, in humans, "breathing an oxygen deficient atmosphere can have serious and immediate effects, including unconsciousness after only one or two breaths. The exposed person has no warning and cannot sense that the oxygen level is too low." In the US, at least 80 people died due to accidental nitrogen asphyxiation between 1992 and 2002.〔 Hazards with inert gases and the risks of asphyxiation are well established.〔http://www.asiaiga.org/docs/AIGA%20008_11_Hazards%20of%20inert%20gases%20and%20oxygen%20depletion.pdf〕 An occasional cause of accidental death in humans, inert gas asphyxia with gases including helium, nitrogen, methane, and argon, has been used as a suicide method. Inert gas asphyxia has been advocated by proponents of euthanasia, using a gas-retaining plastic hood device colloquially referred to as a suicide bag. At least 109 people died by suicide by inhaling helium, the most popular inert gas for this use, from 2001 to 2009, in Australia. Nitrogen asphyxiation has been suggested by a number of lawmakers and other advocates as an allegedly more humane way to carry out capital punishment. In April 2015, the Oklahoma Governor Mary Fallin signed a bill authorizing nitrogen asphyxiation as a secondary form of execution.〔(【引用サイトリンク】title=Oklahoma Gov. Mary Fallin signs bill allowing nitrogen asphyxiation as alternative execution method )〕 == Process == When humans breathe in an asphyxiant gas, such as pure nitrogen, helium, neon, argon, sulfur hexafluoride, methane, or any other physiologically inert gas(es), they exhale carbon dioxide without re-supplying oxygen. Physiologically inert gases (those that have no toxic effect, but merely dilute oxygen) are generally free of odor and taste. As such, the human subject detects little abnormal sensation as the oxygen level falls. This leads to asphyxiation (death from lack of oxygen) without the painful and traumatic feeling of suffocation (the hypercapnic alarm response, which in humans arises mostly from carbon dioxide levels rising), or the side effects of poisoning. In scuba diving rebreather accidents, there is often little sensation but euphoria—however, a slow decrease in oxygen breathing gas content has effects which are quite variable.〔 By contrast, suddenly breathing pure inert gas causes oxygen levels in the blood to fall precipitously, and may lead to unconsciousness in only a few breaths, with no symptoms at all.〔 Some species of animals are equipped to detect hypoxia better than humans are, and these species are more uncomfortable in low-oxygen environments that result from inert gas exposure.〔 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「Inert gas asphyxiation」の詳細全文を読む スポンサード リンク
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