Airtight Containers of Crystals for the Poison Gas Zyklon B, Intended for Use at Auschwitz (c. 1942-1945) The poison gas Zyklon B, now the symbol of industrial mass murder, was used mainly in the gas chambers at Auschwitz II-Birkenau. It had been tested on Russian prisoners of war in the main camp as early as September 1941. In the Kulmhof, Belzec, Sobibor, Treblinka, and Majdanek camps, victims were killed chiefly by motor exhaust fumes, but they also died in mass shootings and from carbon monoxide poisoning.