Gas chambers were already used as early as in the 1920’s, for legal executions in some states of the United States where it is still in use today.
Killing by poisonous gas was experimented in National-Socialist Germany from October 1939 on, during the so-called T4 Action. The Aktion T4 (for Tiergartenstrasse 4, in Berlin, where the office stood) aimed at killing the handicapped people whose life had been deemed unworthy (lebensunwertes Leben) by the regime. Significantly, the order, signed by Hitler himself, to execute the mentally and physically disabled was antedated to September 1, 1939, the beginning of the war. For the Nazis, the so-called euthanasia (Gnadentod) was an act of war which aimed at helping the German people get rid of existences that would be a burden in the international struggle for life. In six killing facilities (Tötungsanstalten), gas chambers were built. The poison used was Morphium-Scopolamin and carbon monoxide. Between October 1939 and August 1941, more than 70 000 German handicapped people were killed by gas, after a selection that was made by SS physicians.
That killing method proved satisfactory: gas killed quickly and massively. It was much more rapid and much cheaper than bullets. It made assassination easy compared to firing squads that required many soldiers. The operations could be troubled by revolts, and the hangmen could be traumatized because they saw the faces of the victims. This is exactly what happened to the intervention units (Einsatzgruppen) of the SS and the German Police on the Eastern Front. These mobile firing squads had to follow the front and to secure territories at the rear of the Wehrmacht and Waffen-SS by executing communists and male Jews, then, in the course of the summer of 1941 all Jews, including women, elderly people and children. Inspectors from Berlin often deplored the lack of discipline, the consumption of alcohol, and stated a demoralization that could lead to suicide.
When the decision to kill the European Jews was made, between the summer of 1941 and the Conference of Wannsee (January 20, 1942), gas chambers were experimented in Chelmno (Kulmhof). It was considered as the best way to make the crime possible, because it was the easiest. Firing squads knew they killed, and whom they killed. The use of gas chambers made the scruples of murder and, henceforth, the very notion of responsibility, vanish. Consequently, gas chambers plaid the same role as the euphemizing language the Nazis used to give orders related to the crime: the language rules (Sprachregelungen) spoke of special treatment, not of assassination. The gas chambers made the crime indirect and fragmented: some SS made the selection, some others led the victims to the chamber, others poured the gas crystals into the room and others supervised the cremation. Everybody killed, but indirectly, and, ideally, without ever pulling a trigger or resorting to violence.
The first method, in Chelmno and Auschwitz, was assassination by carbon monoxide exhausted by truck engines. The victims would be placed in a sealed hermetic truck and the exhaust gas would kill them. The problem was the high pressure (that led at least one truck to explode) and the time needed to asphyxiate the prisoners. In Auschwitz, an aide of Lagerkommandant Hoess had the idea of using the pesticide Zyklon B. Impregnated in small crystal substrates, the hydrogen cyanide (prussic acid) was vaporized when it came in contact with air. Poured into the gas chambers, Zyklon B would kill in 6 to 25 minutes, depending on the season, because it needed an ideal temperature of 27°C. In other camps, like Belzec or Treblinka, the carbon monoxide remained in use: the engine of an army tank provided the poison.
Gas chambers in Auschwitz were not visible from the outside. They were hidden in the basement of the crematoria. Selected victims, chosen on the ramp of the camp train terminus, were led to the gas chambers, that were equipped, in Auschwitz, with fake shower heads. This aimed at reassuring the victims, alongside with numerous bath and shower signs written in different languages. In other extermination camps, however, the gas chambers had no such false showers.
As Himmler had given the order in January 1945 to evacuate the camp and to blow the crematoria, the only sources were the testimonies of SS engineer Kurt Gerstein and of Rudolf Hoess. Later, the so-called Sonderkommandos manuscripts were found, documents and photographs buried in the camp by members of the Sonderkommandos, units of prisoners that had to handle the bodies. In the 1990’s, after the archives in the East were opened to historians of the West, French historian Jean-Claude Pressac discovered plans, estimates, contracts of the diverse private companies that worked for the SS. He found the plans concerning the ventilation systems of the gas chambers and of the crematoria of Auschwitz.
A former revisionist, Pressac could thus find the documentary evidence that still missed to contradict those who negated, and still deny, the reality of the Holocaust.
Gas chambers were the heart of the national-socialist death industry. They were situated directly under the crematoria to ensure maximum efficiency and rapidity. Built in extermination camps, they were present in some concentration camp as well, for special executions: Mauthausen, Sachsenhausen, Ravensbrück, Stutthof, Neuengamme, Natzweiler, and Dachau were equipped with gas chambers and crematoria, although the camps were not designed for mass killings.
The Nazis were eager to hide the reality or swipe the evidence of the crime: they destroyed the crematoria in Auschwitz and they erased the camps of Belzec and Treblinka. They were, in a way, the first revisionists, or, as French historians say, negationists. Gas chambers became the main arguing point of the revisionist discourse: as they all were successfully destroyed, their existence could not be proved. If the testimony of both victims and hangmen were not evidence enough, archive documents now fully prove it.
BROWNING, Christopher R., 1992, The Path to Genocide: Essays on launching the Final Solution, Cambridge: Cambridge University Press.