The RSHA office II D 3a was responsible for construction, employment, drivers and the provision of spare parts for the gas vans. During WW2 two types were used: small versions with about 3.5t payload for about 50 persons (Diamond, Opel Blitz, and Renault) and bigger ones with approximately 5t payload for around 70 victims (Saurer). The wagons had an air-sealed car-body and looked like furniture vans. With a removable tube the exhaust fumes could be led into the car body. A barred lamp could be used to illuminate the interior.
Prior to gassing, the victims were ordered to hand over their valuables. They then had to undress and finally entered the gas vans. The two doors at the back of the wagons were closed, and the tube then locked to the exhaust. To calm down the naked victims a lamp was switched on for some minutes. The driver then started the motor, which ran in neutral gear for about ten minutes. During this time the motor produced enough carbon monoxide to suffocate the victims. As they were so crowded together there was lack of air anyway. When the screaming and pounding had stopped, the driver started the drive to the cremation site. There Jewish men, who would not be permitted to remain alive, were forced to unload the corpses and cremate them.
Sometimes the victims were gassed at the site of their mass grave; e.g. in Stalino where on Easter Monday 1942 200 - 300 Jews were killed in gas vans and their corpses pushed into the shaft of a coal mine.
Gas vans were used on a large scale by the Einsatzgruppen in Byelorussia and the Ukraine. Here thousands of persons, mainly Jews, were killed by the use of these wagons. For example, thousands of Jews from the Minsk Ghetto lost their lives in gas vans which were stationed at the extermination site Maly Trostinec, 12 km southwest of Minsk.
Eberhard von Thadden, a Foreign Office official who succeeded Franz Rademacher as head of the Jewish desk, noted in his diary a visit by representatives of the Italian Fascist Party to Generalkommissar Wilhelm Kube in Minsk on 15 May 1943. Kube showed the visitors a church that was being used as a warehouse. The diary entry continues:
"The Italians asked about the little packages and suitcases that were piled up in the church. Kube explained that this was all that was left of the Jews who had been deported from Minsk. Then he showed them a gas chamber in which he said Jews had been gassed. The Fascists were severely shaken."
At least 152,000 people were gassed by the use of gas vans at the Chelmno extermination camp near Lodz.
source:
http://www.deathcamps.org/gas_chambers/gas_chambers_vans.html
