What were the gas vans? When and where were they used?

Gas vans were trucks used to asphyxiate Jews and others. At first, the carbon monoxide generated by the combustion of gasoline by the trucks' engines was channeled into sealed chambers. This method was initially used as part of the "euthanasia" program, in which the Nazis killed physically and mentally handicapped Germans. Later, in September 1941, Soviet prisoners of war were murdered in Sachsenhausen by channeling the fumes into the sealed compartment of the truck itself. Two months later, mobile gas vans were put into use in the Soviet Union as part of the murder of Jews spearheaded by the Einsatzgruppen. When the Chelmno extermination camp was established in December 1941, gas vans were used there as well. Gas vans were used in the murder of approximately 700,000 people throughout Nazi-dominated Europe.