Zyklon B was a commercial pesticide before becoming a tool of industrial mass murder.

Nature · Published 29 September 2026 Swipe more like this →

In short: Originally developed in the 1920s as a cyanide-based fumigant for ships and warehouses, Zyklon B was later repurposed by the Nazi regime. While its manufacturers marketed it as a civilized method for delousing, it became the primary instrument for the systematic murder of approximately 1.1 million people during the Holocaust.

Zyklon B was the trade name for a pesticide consisting of hydrogen cyanide, a stabilizer, and a cautionary eye irritant. Developed by chemists at the German firm Degesch—including Walter Heerdt and Bruno Tesch—the product was designed to release poisonous gas upon exposure to air. Throughout the 1920s and 1930s, it was used globally for fumigating trains, ships, and clothing. In the United States, it was even used at customs facilities along the Mexican border to treat the belongings of immigrants.

The chemical mechanism of Zyklon B is lethal because it disrupts cellular respiration. Hydrogen cyanide binds to cytochrome c oxidase, a protein involved in the electron transport chain, specifically at the heme a3 iron group. This binding prevents cells from producing adenosine triphosphate, the energy currency of life. A human weighing 68 kilograms can die within two minutes of inhaling 70 milligrams of the gas. The Nazis, who prided themselves on being civilized killers, adopted this method in early 1942, viewing it as a more efficient and humane alternative to previous killing methods.

The scale of its use was immense. Between 1942 and 1944, roughly 729 tonnes of Zyklon B were sold in Germany, with about 8 percent of that supply—approximately 56 tonnes—delivered to concentration camps like Auschwitz-Birkenau and Majdanek. After the war, the product's horrific association led to intense public scrutiny of companies that reused the name or its derivatives. Holocaust deniers have attempted to argue against the use of Zyklon B in gas chambers by citing flawed chemical tests, but forensic re-examinations have consistently confirmed the presence of cyanide residue in the gas chambers, refuting these claims.

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