Loss of consciousness may be accompanied by convulsions and is followed by cyanosis and cardiac arrest. About 7 minutes of oxygen deprivation causes death of the brainstem.{{citation needed|date=March 2018}}

Animal slaughter

Relation to controlled atmosphere killing

Euthanasia of animals

Diving animals such as mink and burrowing animals, such as rodents and rats, are sensitive to low-oxygen atmospheres and (unlike humans) will avoid them, making purely hypoxic techniques possibly inhumane{{Citation needed|date=August 2017}} for them. For this reason, the use of inert gas (hypoxic) atmospheres (without CO₂) for euthanasia, is also species-specific.^[10][11]

Accidental deaths and injury

Accidental nitrogen asphyxiation is a possible hazard where large quantities of nitrogen are used. It causes several deaths per year in the United States,^[25] which is asserted to be more than from any other industrial gas. In one accident in 1981, shortly before the launch of the first Space Shuttle mission, five technicians lost consciousness and two of them died after they entered the Orbiter aft compartment. Nitrogen had been used to flush oxygen from the compartment as a precaution against fire. They were not wearing air packs because of a last-minute change in safety procedures.^[26]

During a pool party in Mexico in 2013, eight party-goers were rendered unconscious and one 21-year-old male was put into a coma after liquid nitrogen was poured into the pool.^[12][13]

Occasional deaths are reported from recreational inhalation of helium, but these are very rare from direct inhalation from small balloons. The inhalation from larger helium balloons has been reportedly fatal.^[14] A fatal fall from a tree occurred after the inhalation of helium from a toy balloon, which caused the person to become either unconscious or light headed.^[15]

In 2015, a technician at a health spa was asphyxiated while conducting unsupervised cryotherapy using nitrogen.^[16][17]

Suicide

Use of inert gas for suicide was first proposed by a Canadian, Dr Bruce Dunn.^[18] Dunn commented that, "...the acquisition of a compressed gas cylinder, an appropriate pressure reducing regulator, and suitable administration equipment... [was] "not inaccessible to a determined individual, but relatively difficult for a member of the public to acquire casually or quickly."^[19] Dunn collaborated with other researchers, notably the Canadian campaigner, John Hofsess, who in 1997 formed the group "NuTech" with Derek Humphry and Philip Nitschke.^[20] Two years later, NuTech had streamlined Dunn's work by using readily-available party balloon cylinders of helium.^[21]

The method of suicide based on self-administration of helium in a bag, a colloquial name being the "exit bag" or suicide bag, has been referenced by some medical euthanasia advocacy groups.^[22] Originally such bags were used with helium, and 30 deaths were reported with use of them from 2001 to 2005, and another 79 from 2005 to 2009. This suggested to one set of reviewers that the popularity of the technique was increasing, as also did the increase in helium suicides in Sweden during the latter half of the same decade.^[38]

After attempts were made by authorities to control helium sales in Australia, a new method was introduced that instead uses nitrogen.^[23] Nitrogen became the main gas promoted by euthanasia advocates, such as Philip Nitschke, who founded a company called Max Dog Brewing in order to import canisters of nitrogen into Australia.^[24] Nitschke stated that the gas cylinders can be used for both brewing and, if required, to end life at a later stage in a "peaceful, reliable [and] totally legal" manner.^[25] Nitschke said, "[nitrogen] was undetectable even by autopsy, which was important to some people".^[26]

Capital punishment

Execution by nitrogen asphyxiation was discussed briefly in print as a theoretical method of capital punishment in a National Review article, "Killing with kindness – capital punishment by nitrogen asphyxiation".^[43] The idea was then proposed by Lawrence J. Gist II, an attorney at law, under the title, International Humanitarian Hypoxia Project.^[27]

In a televised documentary in 2007, the British political commentator and former MP Michael Portillo examined execution techniques in use around the world and found them unsatisfactory; his conclusion was that nitrogen asphyxiation would be the best method.^[45]

In April 2015, Governor Mary Fallin of Oklahoma signed a bill allowing nitrogen asphyxiation as an alternative execution method.^[3] Three years later, in March 2018, Oklahoma announced that, due to the difficulty in procuring lethal injection drugs, nitrogen gas would be its primary method of carrying out executions.^[28] In March 2018, Alabama became the third state (along with Oklahoma and Mississippi), to authorize the use of nitrogen asphyxiation as a method of execution.^[29]

See also

• Asphyxiant gas
• Gas chamber
• Capital punishment
• Animal slaughter

Notes