How did Zyklon B chemically kill people and what are its active components?
Executive summary
Zyklon B was a commercial pesticide whose lethal agent was hydrogen cyanide (HCN); in pellet form it released HCN gas when exposed to air, killing by blocking cellular respiration at the mitochondrial level and rapidly depriving tissues of usable oxygen [1] [2] [3]. The product combined HCN with a warning irritant and a solid adsorbent carrier (variously diatomaceous earth or similar materials) supplied by German chemical firms and repurposed by the SS for mass murder in Nazi camps [1] [4] [3].
1. What Zyklon B actually contained: hydrogen cyanide, an irritant, and a carrier
The marketed formulation called Zyklon B consisted principally of hydrogen cyanide (prussic acid, HCN) impregnated into a solid carrier together with a cautionary eye‑irritant to signal accidental exposure; historical company and patent records and contemporary summaries list HCN as the active toxicant, a bromoacetic‑ester warning agent, and adsorbents such as diatomaceous earth or analogous mineral carriers [1] [4] [2].
2. How the pellets became a lethal gas: release mechanics and storage
Manufactured and shipped as sealed canisters of blue‑colored pellets, Zyklon B was designed to release gaseous HCN when the pellets were exposed to air (and in some formulations on contact with moisture and heat), so that simple opening or dispersal of pellets in a confined space produced a rapid vapor concentration of hydrocyanic acid [2] [1] [4].
3. The biochemical kill mechanism: blocking cellular respiration
Hydrogen cyanide kills by binding to the iron center of cytochrome oxidase in mitochondria, interrupting electron transfer to oxygen and halting oxidative phosphorylation; this molecular block prevents cells from using oxygen, causing failure of energy metabolism and rapid injury to lungs, blood vessels, heart, and ultimately the brain — organ systems most sensitive to hypoxic metabolic collapse [3].
4. Symptoms, speed, and conditions that made it effective for mass murder
In confined, poorly ventilated chambers HCN reaches lethal concentrations quickly and causes asphyxia-like death even when ambient oxygen is present because cells cannot utilize that oxygen; historical and forensic accounts emphasize the agent’s rapid onset and the efficiency of pellet dispersion in enclosed spaces as reasons Zyklon B was adopted for mass killing [3] [5] [2].
5. Who made and supplied it, and the historical context of its use
Zyklon B was developed in the 1920s by German chemical firms and distributed by Degesch and related companies (with involvement of Degussa and suppliers such as Tesch), originally as a pest control and disinfection product; from 1941 onward the SS obtained the product for use in disinfecting installations and ultimately for systematic gassing operations in concentration and extermination camps, where historians estimate well over a million victims were killed with hydrogen cyanide released from Zyklon B [1] [3] [4] [6].
6. Debates, forensic traces, and limitations of chemical evidence
Scholars and investigators note two important caveats: first, the carrier materials varied and analyses of surviving pellets show differences (some studies emphasize calcium sulfate or other carriers rather than pure diatomaceous earth), so composition details can differ by batch and manufacturer [7]. Second, absence of long‑term chemical residues in masonry has been used in contested technical arguments about chamber use, but toxicological and environmental chemistry experts explain that HCN does not necessarily leave persistent, easily detectable residues under all conditions — a forensic complexity discussed in specialized investigations [8].