During the Holocaust, Nazi Germany extensively used gas chambers for mass murder. Beginning in 1939, gas chambers were part of Aktion T4, an "euthanasia" program targeting people with disabilities. By 1940, six killing centers in Germany used bottled carbon monoxide for these murders. The Einsatzgruppen used gas vans for executions during the Soviet Union invasion. From 1941, extermination camps in Poland, such as Chełmno, Bełżec, Sobibór, and Treblinka, employed various gas methods, including exhaust fumes and Zyklon B. At Auschwitz, Zyklon B was used for mass murder, killing up to 6,000 people daily. #WHOLESALE WEEK