Albert Widmann with the car engine running. He had nearly died of carbon monoxide poisoning from the exhaust fumes. This engine exhaust testing inspired the development of gas vans. Back in Berlin, Reinhard Heydrich immediately set to work within the RSHA for the development of, in the words of Heydrich's subordinate Walter Rauff, a "more humane method of execution" than the "Einsatzgruppen" firing squads which had been used. When a prototype gas van was driven to KTI, Widmann explained to his young chemists that by adjusting the timing of the ignition, one could maximize the amount of poisonous carbon monoxide in the
Extermination camp the German civil populace. During the initial phase of the Final Solution, gas vans producing poisonous exhaust fumes were developed in the occupied Soviet Union (USSR) and at the Chełmno extermination camp in occupied Poland, before being used elsewhere. The killing method was based on experience gained by the SS during the secretive "Aktion T4" programme of involuntary euthanasia. There were two types of death chambers operating during the Holocaust. Unlike at Auschwitz, where the cyanide-based Zyklon-B was used to exterminate trainloads of prisoners under the guise of "relocation", the camps at Treblinka, Bełżec, and Sobibór, built during Operation Reinhard