Nitrogen asphyxiation is an occasional cause of accidental death and a theoretical method of capital
punishment advocated in a National Review article, "Killing with kindness – capital punishment by nitrogen
asphyxiation." (Creque 1995) The painful experience of suffocation is not caused by lack of oxygen intake but rather
because of a buildup of carbon dioxide in the bloodstream which is exhaled under normal circumstances.
When a human
breathes in pure nitrogen, they exhale carbon dioxide without resupplying oxygen. Nitrogen is a colorless, odorless and tasteless
gas that comprises approximately 78 percent of the Earth's atmosphere. As such, the subject would detect no abnormal sensation.
This leads to asphyxiation without the painful and traumatic feeling of suffocation. This effect occurs in humans, but may
be very unpleasant for burrowing animals such as rodents or rabbits, which have better function of the carotid body receptors
For this reason, accidental nitrogen asphyxiation is a possible hazard where large quantities of nitrogen
are used. Also, deliberate nitrogen asphyxiation is viewed by some as a more humane way to end a human life in a controlled
setting. As the principal component in air, nitrogen poses no significant risk upon discharge.
Other inert asphyxiant
gases such as helium or argon produce identical effects, but nitrogen is least expensive.
of capital punishment proposed use
There are substantial moral arguments against
and in favor of capital punishment by any means. Although execution by nitrogen asphyxiation was discussed briefly in print
more than 10 years ago (Creque 1995) and circulates in various online forums, it is not presently used by any nation. Switching
to this procedure would require a change of law. Legislative debate on such a proposal could focus public attention and provide
opponents a forum to argue for abolition (Seitz 2001).
In a televised documentary in 2007 , the right-wing UK political
commentator (and former Member of Parliament United Kingdom), Michael Portillo examined execution techniques in use around
the world and found them unsatisfactory ; his conclusion was that nitrogen asphyxiation would be the least-worst method.
If reintroduction of the death penalty were ever to return to the political agenda in the UK, this would be a significant
contribution to the debate.
As breathing is an absolute requirement for human life, no physical condition of a living
subject can prevent the prompt completion of this procedure. Properly condemned individuals could be executed without physical
trauma and without the arguably unethical use of medical skill, essentially by withdrawing life support. Some people experience
claustrophobia when presented with an anesthetic gas mask before surgery, and some subjects might react similarly. Nitrogen
could be introduced into a standard gas chamber, however, without difficulty.
Execution by lethal injection, in contrast,
requires medical skill and has occasionally been prolonged when it was difficult to insert the injection needle into an open
Evidence from cases of accidental death from nitrogen asphyxiation
Accidental nitrogen asphyxiation causes about 8 deaths per year in the United States, which is asserted
to be more than from any other industrial gas. For example in 1981, shortly before the launch of the first Space Shuttle mission,
two technicians lost consciousness and died after they entered the Orbiter aft compartment which was pressurized with pure
nitrogen as a precaution against fire.
A laboratory assistant died in Scotland in 1999, apparently from asphyxiation,
after liquid nitrogen spilled in a basement storage room.
of impending death
Every condemned individual is aware of impending death
in general, as a result of court proceedings, transport to the execution site, and preparation of the execution equipment.
At the shortest time scale, however, nitrogen asphyxiation provides little warning of the moment when final unconsciousness
A typical human breathes between 12 and 20 times per minute at a rate primarily
influenced by carbon dioxide concentration, and thus pH, in the blood. With each breath, a volume of about 0.6 liters is exchanged
from an active lung volume (tidal volume + functional residual capacity) of about 3 liters. Normal air is about 78 percent
nitrogen, 21 percent oxygen, and 1 percent argon, carbon dioxide, and other gases. After just two or three breaths of nitrogen,
the oxygen concentration in the lungs would be low enough for some oxygen already in the bloodstream to exchange back to the
lungs and be eliminated by exhalation. Crude simulation of oxygen transport through the lungs and blood stream suggests that
the partial pressure of oxygen in arterial blood would be about 50 percent of saturation 1 minute after switching gases and
would reach zero within 3 minutes.
Unconsciousness in cases of accidental asphyxia can occur within 1 minute. Loss of
consciousness results from critical hypoxia, when arterial oxygen saturation is less than 60% (Fisher n.d.). “At oxygen
concentrations [in air] of 4 to 6%, there is loss of consciousness in 40 seconds and death within a few minutes” (DiMaio
& DiMaio 2001:231). As this procedure provides an atmosphere completely devoid of oxygen, the sequence of effects should
be expected to occur even more quickly. At an altitude greater than 43,000 ft (13,000 m), where the ambient oxygen concentration
is equivalent to 3.6% at sea level, an average individual is able to perform flying duties efficiently for only 9 to 12 seconds
without oxygen supplementation (Fisher n.d.). The US Air Force trains air crews to recognize their individual subjective signs
of approaching hypoxia. Some individuals experience headache, dizziness, fatigue, nausea, or euphoria, but some become unconscious
without warning (Fisher n.d.). Equivalent training is unlikely for a condemned individual, making unconsciousness without
warning probable, although as much as a 30 second warning is possible.
Loss of consciousness may be accompanied by convulsions
(Fisher n.d.) and is followed by cyanosis and cardiac arrest. About 7 minutes of oxygen deprivation causes death of the cerebral
cortex and presumably the medulla oblongata, which controls breathing and heart action.