What chemicals were used in Nazi gas chambers and how did they kill victims?
Executive summary
Nazi murderers used mainly two chemical approaches in gas killings: hydrogen cyanide delivered as Zyklon B pellets and carbon monoxide delivered either from cylinders or engine exhaust; Zyklon B (hydrogen cyanide, HCN) became the primary killing agent in extermination camps from late 1941 and was responsible for roughly 1.1 million deaths at Auschwitz and other camps [1] [2] [3]. Carbon monoxide—both “chemically pure” from canisters and as vehicle/stationary engine exhaust—was used earlier and in mobile gas vans and some killing centers [1] [4] [5].
1. The two main chemical methods: HCN (Zyklon B) and carbon monoxide
Historical records and museum accounts identify two distinct lethal gases used by the Nazis. Zyklon B is a commercial formulation whose lethal component is hydrogen cyanide (HCN); it was supplied as pellets that released HCN on exposure to air and was used in Auschwitz, Majdanek and other camps [3] [2]. Separately, carbon monoxide was used either as bottled, chemically pure gas or generated by engines in gas vans and some fixed chambers—this method was used in Aktion T4 euthanasia killings and at sites including Chelmno and Aktion Reinhard camps [1] [4] [5].
2. How hydrogen cyanide killed people inside chambers
Zyklon B pellets released hydrogen cyanide gas when exposed to air; SS personnel dropped pellets into sealed rooms or through ceiling openings and victims inhaled HCN. Hydrogen cyanide blocks cellular respiration by inhibiting key enzymes such as cytochrome c oxidase (technical biochemical detail in clinical literature; sources here describe the rapid, convulsive, and painful effects observed), producing violent convulsions, respiratory collapse, and cardiac arrest within minutes in the concentrations used by the Nazis [6] [7] [8].
3. How carbon monoxide killed victims in vans and chambers
Carbon monoxide (CO) causes death by binding hemoglobin and preventing blood from carrying oxygen; in the sealed confines of vans or chambers, CO concentrations rose rapidly and produced hypoxia and loss of consciousness followed by death. The Nazi record distinguishes between chemically pure CO from canisters used in early Aktion T4 murders and CO produced by diesel or petrol engines used later in gas vans and some camps [1] [4] [5].
4. Practicalities, deception, and the industrial apparatus of killing
Survivor testimony and camp documentation show the Nazis disguised gas chambers as showers or disinfection rooms to herd victims inside, then introduced Zyklon B pellets through openings or piped in exhaust or bottled CO; crematoria and ventilation systems were then used to remove bodies and conceal operations—this logistical “efficiency” was central to the industrial scale of the crime [8] [9] [7].
5. Scale and timing: when each agent was used
Zyklon B was experimented with at Auschwitz in September 1941 and became the primary extermination tool in many camps by 1942–43; multiple sources estimate roughly 1.1 million people were killed in gas chambers with Zyklon B at Auschwitz-Birkenau and other sites [6] [2] [10]. Carbon monoxide methods—gas vans and piped CO—were used earlier and concurrently in other killing operations such as Chelmno and Aktion Reinhard camps [1] [4].
6. Contested claims, denial attempts, and forensic responses
Holocaust deniers have pointed to chemical residue arguments (e.g., the Leuchter report) to dispute Zyklon B use for killing; institutions and forensic studies have rebutted these claims, noting differences between delousing and extermination uses, ventilation, exposure times, and weathering of ruins, and citing chemical analyses and eyewitness testimony that confirm HCN’s use to kill people [11] [12] [13].
7. Modern echoes and why chemical specifics matter
Contemporary controversies—such as U.S. states seeking materials to produce cyanide gas—revive the moral and historical weight of these chemicals because Zyklon B/HCN is indelibly associated with mass murder in the Holocaust; reporting cites survivors, museums, and historians who quantify the deaths tied to HCN at Auschwitz and other camps to explain why the association is so fraught [14] [15] [10].
Limitations and sourcing note: this account summarizes facts and survivor/testimony-based histories documented by Holocaust museums, academic histories, and contemporaneous reports provided in the sources above; available sources do not mention detailed clinical enzyme mechanics beyond noting the rapid, convulsive, and asphyxiating effects of HCN and the oxygen-blocking effect of CO as reported in historical accounts [6] [1].