Agas chamber is an apparatus for killing humans or animals with gas, consisting of a sealed chamber into which apoisonous orasphyxiant gas is introduced. Poisonous agents used includehydrogen cyanide andcarbon monoxide. High concentrationcarbon dioxide is typically used in gas chambers for animals.
In America, the utilization of a gas chamber was first proposed byAllan McLane Hamilton to the state of Nevada.[1][2][3][4] Since then, gas chambers have been used as a method of execution of condemned prisoners in the United States and continue to be a legal execution method in three states, seeinglegislated reintroduction with inert N2, although redundant in practice since the early 1990s.[5]Lithuania used gas chambers for civilian, penal use in the 1930s, with the last known execution carried out in 1940. None of these saw mass use, however, and were strictly for "criminal" purposes.
Most notably, duringthe Holocaust large-scale gas chambers designed for mass killing were used byNazi Germany from the late 1930s, as part of theAktion T4, and later for itsgenocide program.
More recently, escapees fromNorth Korea have alleged executions to have been performed by gas chamber in prison camps, often combined withmedical experimentation.[6]
Nazi Germany made extensive use of various types of gas chambers for mass-murder duringthe Holocaust.
Beginning in 1939, gas chambers were used as part ofAktion T4, an "involuntary euthanasia" program under which the Nazis murdered people with physical and intellectual disabilities, whom the Nazis considered"unworthy of life". Experiments in the gassing of patients were conducted in October 1939 in occupiedPoznań in Poland. Hundreds of prisoners were murdered bycarbon monoxide poisoning in an improvised gas chamber.[7] In 1940, gas chambers using bottled pure carbon monoxide were established at six killing centres in Germany.[8] In addition to persons with disabilities, these centres were also used duringAction 14f13 to murder prisoners transferred from concentration camps in Germany, Austria, and Poland. Concentration camp inmates continued to be murdered even after the euthanasia program was officially shut down in 1941.[9]
During theinvasion of the Soviet Union, mass executions byexhaust gas were performed byEinsatzgruppen usinggas vans, trucks modified to divert engine exhaust into a sealed interior gas chamber.[8]
Starting in 1941, gas chambers were used atextermination camps in Poland for the mass-murder ofJews,Roma, and other victims ofthe Holocaust. Gas vans were used at theChełmno extermination camp. TheOperation Reinhard extermination camps atBelzec,Sobibor, andTreblinka used exhaust fumes from stationarydiesel engines.[8]
In search of more efficient killing methods, the Nazis experimented with using thehydrogen cyanide-basedfumigantZyklon B at theAuschwitz concentration camp. This method was adopted for mass-murder at the Auschwitz andMajdanek camps. Up to 6,000 victims were gassed with Zyklon B each day at Auschwitz.[8]
Most extermination camp gas chambers were dismantled or destroyed in the last months ofWorld War II asSoviet troops approached, except for those atDachau,Sachsenhausen and Majdanek. One destroyed gas chamber at Auschwitz was reconstructed after the war to stand as a memorial.
Kwon Hyok, a former head of security atCamp 22, described laboratories equipped with gas chambers forsuffocation gas experiments, in which three or four people, normally a family, are the experimental subjects.[12][13] After the chambers are sealed and poison is injected through a tube, while scientists observe from above through glass. In a report reminiscent of an earlier account of a family of seven, Kwon claims to have watched one family of two parents, a son and a daughter die from suffocating gas, with the parents trying to save the children usingmouth-to-mouth resuscitation for as long as they had the strength. Kwon's testimony was supported by documents from Camp 22 describing the transfer of prisoners designated for the experiments. The documents were identified as genuine by Kim Sang Hun, a London-based expert on Korea and human rights activist.[14]
In 1937–1940,Lithuania operated a gas chamber inAleksotas within the First Fort of theKaunas Fortress.[15] Previous executions were carried out by hanging or by shooting. However, these methods were viewed as brutal and in January 1937, the criminal code was amended to provide execution by gas which at the time was viewed as more civilized and humane. Lithuania considered and rejected execution by poison. Unlike the American or German model the Lithuanian gas chamber, built out of bricks, worked by inputting compressed lethal gas from an external storage cylinder (Černevičiūtė 2014). The first execution was carried on July 27, 1937: Bronius Pogužinskas, age 37, convicted of murder of five people from a Jewish family.[15] Historian Sigita Černevičiūtė counted at least nine executions in the gas chamber, though records are incomplete and fragmentary. Of the nine, eight were convicted of murder. One of these, Aleksandras Maurušaitis, was also convicted of anti-government actions during the1935 Suvalkija strike. The last known execution took place on May 19, 1940, for robbery. The fate of the gas chamber after theoccupation by the Soviet Union in June 1940 is unclear.[15]
As historianRobert Gellately pointed out, "the Soviets sometimes used a gas van (dushegubka), as in Moscow during the 1930s [...], but had no gas chambers."[16] In interrogations in the late 1930s,NKVD officers had testified that special trucks called "soul takers" (dushegubki) were supposed to carry prisoners to their executions but instead gassed them on their way by channeling exhaust fumes into the compartment where the prisoners were held.[17] AuthorTomasz Kizny assumes that they were in use while NKVD officer Isai Berg oversaw the executions atButovo (October 1937 to 4 August 1938).[18]Berg is quoted that "there was no other way to execute so many people". According to yet another contemporary this was only a precautionary method aimed at preventing riots. HistorianIgal Halfin notes, that execution by gas is never mentioned in other Soviet sources, and it contradicts the Soviet practice of individualized executions.[17]
Gas chambers have been used forcapital punishment in the United States to executedeath row inmates. The first person to be executed in the United States by lethal gas wasGee Jon, on February 8, 1924. An unsuccessful attempt to pump poison gas directly into his cell atNevada State Prison led to the development of the first makeshift gas chamber to carry out Jon's death sentence.[19]
On December 3, 1948,Miran Thompson andSam Shockley were executed in the gas chamber atSan Quentin State Prison for their role in theBattle of Alcatraz.
In 1957,Burton Abbott was executed as the governor of California,Goodwin J. Knight, was on the telephone to stay the execution.[20]
Since the restoration of the death penalty in the United States in 1976, 11 executions by gas chamber have been conducted. Four were conducted inMississippi, 2 inArizona, 2 inCalifornia, 2 inNorth Carolina, and 1 inNevada. The first execution via gas chamber since the restoration of the death penalty was in Nevada in 1979, whenJesse Bishop was executed for murder. The most recent execution via gas chamber was in 1999.[21] By the 1980s, reports of suffering during gas chamber executions had led to controversy over the use of this method.[22]
At the September 2, 1983, execution ofJimmy Lee Gray inMississippi, officials cleared the viewing room after 8 minutes while Gray was still alive and gasping for air. The decision to clear the room while he was still alive was criticized by hisattorney. In 2007,David Bruck, an attorney specializing in death penalty cases, said, "Jimmy Lee Gray died banging his head against a steel pole in the gas chamber while reporters counted his moans."[23]
During the April 6, 1992, execution ofDonald Eugene Harding inArizona, it took 11 minutes for death to occur. The prison warden stated that he would quit if required to conduct another gas chamber execution.[24] Following Harding's execution, Arizona voted that all persons condemned to death after November 1992 would be executed bylethal injection.[22]
Following the execution ofRobert Alton Harris in 1992, a federal court declared that "execution by lethal gas under the California protocol is unconstitutionallycruel and unusual."[25] However, this decision was vacated after California amended its statute to allow death row inmates to choose between lethal injection and the gas chamber.[26] By the late 20th century, most states had switched to methods considered to be more humane, such as lethal injection. California's gas chamber at San Quentin State Prison was converted to an execution chamber for lethal injection.[when?]
As of 2020, the last person to be executed in the gas chamber was German nationalWalter LaGrand, sentenced to death before 1992, who was executed inArizona on March 3, 1999. TheU.S. Court of Appeals for the Ninth Circuit had ruled that he could not be executed by gas chamber, but the decision was overturned by theUnited States Supreme Court.[22] The gas chamber was formerly used inColorado,Maryland,Nevada,New Mexico,North Carolina andOregon. Seven states (Alabama, Arizona, California, Mississippi,Missouri, Oklahoma, andWyoming) authorize lethal gas if lethal injection cannot be administered, the condemned committed their crime before a certain date, or the condemned chooses to die in the gas chamber.[27] Alabama, Mississippi, and Oklahoma specify the nitrogen hypoxia method, Arizona specifies the hydrogen cyanide method, and the other states do not specify the type of gas.[28] In October 2010,Governor of New YorkDavid Paterson signed a bill rendering gas chambers illegal for use byhumane societies and other animal shelters.[29]
Gas chambers are used in the slaughter process of animals, particularly pigs and chickens. They are used on groups of animals reducing the need to handle each animal individually, and is relatively inexpensive when applied at scale.[30]
In slaughterhouses in the UK, pigs must be killed by the gas in the chamber.[31] In other countries, pigs may be stunned using the gas chamber first. While unconscious, the pigs are then killed with a sharp knife outside of the gas chamber.[32]
In 2024 in England and Wales, 90% of pigs killed in a slaughterhouse were stunned with this high concentration CO2 method. Chickens, both broiler (77%) and spent egg laying hens (99%), are also frequently stunned in slaughterhouse gas chambers, with a lower CO2 mixture.[33]
The high concentrationCO2 gas typically used is highly aversive and painful to pigs, and still takes at 47-60 seconds on average to stun them in test conditions. The pain and distress of high CO2 concentrations is caused by irritation mucous membranes such as the eyes, mouth and airways, distress, and causes pigs to show aversive behaviours such as gasping, vocalization, and trying to escape. For these reasons, theEuropean Food Safety Authority concluded that CO2 stunning is not optimal from an animal welfare perspective.[34]
Alternatives using inert gas instead of high concentration gas have been successfully tested. Argon was found to be most promising, as the pigs' aversion to the gas was strongly reduced, retrofitting existing gas chambers is possible, and relatively quick. However this method takes longer, raising costs per pig 2-3 fold compared to high concentration CO2, and meat quality differed between trial, having higher numbers of blood spots.[35][36]
The hydrogen cyanide gas chamber is considered to be the most dangerous, most complicated, most time-consuming and most expensive method of administering the death penalty.[37][38][39] It is also notoriously impossible to halt once initiated, which has occurred in the case of stays, such as in the case ofBurton Abbott.[40][41][42] The same event supposedly occurred in the final, completed execution ofCaryl Chessman in 1960.[43] The condemned person is strapped into a chair within an airtight chamber, which is then sealed. The executioner activates a mechanism which dropspotassium cyanide (orsodium cyanide)[44][45] pellets into a bath ofsulfuric acid beneath the chair; the ensuing chemical reaction generates lethalhydrogen cyanide gas.
The condemned is advised to take several deep breaths to speed unconsciousness. Nonetheless, the condemned person often convulses and drools and may also urinate, defecate, and vomit.[46][47]
Following the execution the chamber is purged with air, and any remnant gas is neutralized withanhydrous ammonia, after which the body can be removed (with great caution, as pockets of gas can be trapped in the victim's clothing).[48]
Nitrogen gas or oxygen-depleted air has been considered for human execution, as it can inducenitrogen asphyxiation. The victim detects little abnormal sensation as the oxygen level falls. This leads toasphyxiation (death from lack of oxygen) without the painful and traumatic feeling of suffocation, or the side effects of poisoning.[49]
In April 2015,Oklahoma GovernorMary Fallin approved a bill allowing nitrogen asphyxiation as an execution method.[50] On March 14, 2018, Oklahoma Attorney GeneralMike Hunter and Corrections DirectorJoe M. Allbaugh announced a switch to nitrogen gas as the state's primary method of execution.[51] After struggling for years to design a nitrogen execution protocol, the State of Oklahoma announced in February 2020 that it was abandoning the project after finding a reliable source of drugs to carry out the lethal injection executions.[52]
In 2018, Alabama approved nitrogen asphyxiation as an execution method and allowed death row inmates a choice of method. In September 2022, a court stayed theexecution of Alan Eugene Miller, who was set to be executed by lethal injection. Miller asserted that he had chosen nitrogen hypoxia as his method of execution, as permitted by Alabama law, but the form documenting his choice had been lost. The court decided to stay the execution to allow for further investigation into his claim.[53] On January 25, 2024,Kenneth Eugene Smith became the first person to be executed by nitrogen asphyxiation.[54]
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