In September 1941, Einsatzgruppe B was faced with the task of liquidating the patients of the lunatic asylums in the cities of Minsk and Mogilev. Nebe decided to find a simpler way for his men to kill the mentally diseased, other than by shooting them. He contacted Kripo headquarters and asked for their help in carrying out the killing of the insane with either explosives or poison gas. Dr. Widmann of the Criminal Police was sent to Nebe in Minsk, but before he left, Dr. Widmann discussed with the director of the Criminal Police Technological Institue, Dr. Hess, ways of using the carbon monoxide gas from automobile exhaust for killing operations in the East, based on the experience gained from the euthansia program. Dr, Widmann took to minsk 400 kgs of explosive material and the metal pipes required for the gassing installations.
Nebe and Dr. Widmann carried out an experimental killing using explosives. Twenty-five mentally ill people were locked into two bunkers in a forest outside Minsk. The first explosion killed only some of them, and it took much time and trouble until the second explosion killed the rest. Explosives therefore were unsatisfactory.
A few days later an experiment with poison gas was carried out by Nebe and Dr, Widmann in Mogilev. In the local lunatic asylum, a room with twenty to thirty of the insane was closed hermetically, and two pipes were driven into the wall. A car was parked outside, and one of the metal pipes that Dr. Widmann had brought connected the exhaust of the car to the pipe in the wall. The engine was turned on and carbon monoxide began seeping into the room. After eight minutes, the people in the room were still alive. A second car was connected to the other pipe in the wall. The two cars were operated simultaneously, and a few minutes later all those in the room were dead.
After these experimental executions, Nebe came up with the idea of constructing a car with a hermetically sealed cabin for killing purposes. The carbon monoxide from the car's exhaust would be channeled into the sealed cabin, in which the victims stood. Nebe discussed the technical aspects of the idea with Dr. Hess and together they brought the proposal before Heydrich who adopted it. (1)
The Technical Department of the Reich Security Main Office, headed by SS Obersturmbannfuhrer Walter Rauff, developed a special vehicle for killing purposes. This vehicle resembled an ambulance or refrigerator truck and contained a hermetically sealed rear cabin. The victims were placed in the cabin and carbon monoxide was introduced by means of a pipe. The gassing process took between fifteen and thirty minutes. During this time the van was driven from the loading site to prepared graves.
Two types of gas vans had been built: a larger one, 5.8 meters in length, and a smaller one, measuring 4.5 meters. Both were about 2.5 meters wide and 1.7 meters high. The bigger one could accomodate between 130 and 150 people, when desely packed inside, and the smaller one from 80 to 100. (2)
The gas vans were supplied to the Einsatzgruppen and to the Chelmno death camps in November-December 1941. The killing in Chelmno began on December 8, 1941. By the middle of 1942, about thirty gas vans had been produced by a private car manufacturer, the Gabschat Farengewerke GMBH, Will=Walter Strasse 32-38, Berlin. (3)
A few weeks before the first gas vans were supplied to the Einsatzgruppen, in late October 1941, Dr. Alfred Wetzel of the Ministry for the Eastern Occupied Territories wrote to the Reichskimmissar for Ostland, Hinrich Lohse, of a proposal made by Viktor Brack to set up permanent gassing facilities in Ostland for mass extermination based on experience and help of the euthansia program. With the cessation of the euthansai program in Germany, its personnel were available and looking for new tasks. (4)
The permanent gassing facilities were intended to lighten the task of Nazi authorities in the occupied territories of the Soviet Union in carrying out their killing operations. But the proposal of Dr. Wetzel and of Brack was not implemented in Ostland. The unemployed 'euthansia' personnel were assigned to another and bigger task - the erection of camps with gassing facilities, where annihilation of the Jews in the Nazi-occupied territories of Poland would be carried out. The successful experiments in Auschwitz and the development of the gas vans had provided the solution of the technical problems involved.
(2) Edward Serwanski, Oboz Zaglady w Chelmnie nad Narem (herafter Chelmno), Poznan, 1964, p. 45; Nationalsozialistische Massentotungen, p. 84, gives the number of 50 - 60 people in the Saurer and 25 - 30 people in the Diamond car.
(3) Nationalsozialistische Massentotungen, pp. 84 - 86
(4) Nuremberg Documents, PS-510
Sources: Arad, Yitzak. Belzec, Sobibor, Treblinka: The Operation Reinhard Death Camps. IN: Indiana University Press, 1987, pp. 10-11, and Electric Zen: An Einsatzgruppen Electronic Repository.