Zyklon B

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The gas Zyklon B, developed in Germany in the 1920s, is known the world over, not so much for its reputation as a pesticide as for the aberrant use made of it during World War II at Auschwitz-Birkenau and other German death camps. Indeed, the gas, used to kill an estimated one in six victims in Nazi captivity, has become a symbol of the Holocaust.

Compounded of hydrocyanic acid, also known as prussic acid, together with a stabilizer and irritant, Zyklon B was developed by the German company DEGESCH (Deustche Gesellschaft für Schädlingsbekämpfung), which acquired a patent in 1926 and secured a monopoly for its production and distribution. The gas itself was adsorbed onto granules and packed in canisters of various sizes; highly volatile, it diffused as soon as the canister was opened. Various concentrations were used, depending on the ventilation in the space in which it was to be employed and on the species of parasites that it was intended to kill—whether warm-blooded animals such as rats on ships or in the flour-milling industry, or, more often, insects, especially lice.

Although deadly accidents did occur and severe caution was necessary because prussic acid is extremely dangerous to humans at even low concentrations, Zyklon B was fairly popular as a pesticide in the interwar years. Its high toxicity was the reason it was briefly considered for use in 1939 in the Nazis' secret Aktion T4 program, established to euthanize mental patients, but expert advice settled on carbon monoxide. The first criminal use of Zyklon B at Auschwitz, in September 1941, was largely the result of local initiative and improvisation. When the camp opened in early 1940, the Hamburg firm of Testa was employed to perform delousing fumigations. Testa, one of two companies authorized to conduct these procedures, was again called upon in July 1941. On this occasion, Bruno Tesch, head of Testa, provided the camp's sanitary department supervisors with basic training in the use of the gas. The supervisors, who would actually use Zyklon B, thus learned of its potency.

Around the same time, Auschwitz officials had to deal with the new policy of mass extermination. In July prisoners who were declared unfit to work had been taken to Sonnenstein, near Dresden, to be put to death in the gas chambers there. Following the 17 July 1941 instructions of Reinhard Heydrich, a key SS (Schutzstaffel) figure and planner of the Final Solution, groups of Soviet prisoners of war, selected on the basis of how dangerous they supposedly were, began arriving at Auschwitz, as at other camps, where they were put to death. At this point, the use of Zyklon B represented convergence of a double technological transfer in the service of mass murder. Guards who had escorted prisoners to Sonnenstein returned with the idea of using gas chambers; their supervisors conceived the idea of replacing carbon monoxide by Zyklon B, the product more commonly available at Auschwitz and the lethal character of which they were well-informed.

The first experiments using Zyklon B were performed in September 1941 upon hundreds of Soviet prisoners and on others selected because they were labelled "unfit to work." Improvisation marred this early effort: inasmuch as the dosage was too low, larger quantities of Zyklon B had to be introduced the next morning to finish killing all victims. Poorly ventilated, the basement of Block 11 turned out to be ill-suited to mass execution. Another temporary site was chosen, and, as early as the blueprint stages, care was taken to provide an adequate system for ventilation to the future crematorium of the camp where the gassing would be done.

Over the next several years, the use of Zyklon B in gas chambers spread erratically through the Nazi death camps. It was used to kill Jews and Soviet commissars at Gusen-Mauthausen, Neuengamme, Lublin-Majdanek, Sachsenhausen, Stutthof, and Ravensbrück. However, it was at Auschwitz, where seven metric tons of Zyklon B were used in 1942 and twelve the following year, that the gas was put to its most horrific use. In the spring of 1942, the camp became the regional extermination site for Jews from all the surrounding areas. Bunkers 1 and 2, previously farm cottages, were roughly fitted out as gas chambers.

Nazi leaders then decided that Jews would be transported to Auschwitz from all over Europe. In August 1942 they ordered the construction of four huge gassing facilities together with crematoria, which were first used early in 1943. This extension indicates the astonishing acceleration of the Final Solution, which was conceived as a continent-wide program that had to be carried out swiftly.

To cope with this new pace, Nazi leaders called upon Kurt Gerstein, an expert with the Institute of Hygiene of the Waffen-SS. Gerstein, who later became a key eyewitness to mass murder, was to assess the feasibility of using Zyklon B in place of carbon monoxide in the extermination camps, such as Belzec, Sobitor, and Treblinka, where it was employed until then. Despite its failure, Gerstein's mission proves that, for the high Nazi command, Zyklon B earned its reputation as the best means for accomplishing the Final Solution.

Zyklon B continued to be sold in Germany under its original brand name until 1974.

See alsoAuschwitz-Birkenau; Concentration Camps; Holocaust; War Crimes; World War II.


Brayard, Florent. La "solution finale de la question juive": La technique, le temps et les catégories de la décision. Paris, 2004.

Kalthoff, Jürgen, and Martin Werner. Die Handler Des Zyklon B: Tesch and Stabenow. Eine Firmengeschichte Zwischen Hamburg und Auschwitz. Hamburg, Germany, 1998.

Florent Brayard