Mobile gas chambers
This is one of a series of communications on the problems with “S-Wagons,” written by Dr. August Becker, who made an inspection trip through Eastern Europe to observe their operation. S-Wagons were special vehicles used as mobile gas chambers. The mobile gas chambers were hermetically sealed boxes mounted on truck chassis. Carbon monoxide from the truck's exhaust was pumped into the chamber to kill victims.
National Archives, National Archives Collection of World War II War Crimes Records