A gas van or gas wagon (Russian: душегубка (dushegubka); German: Gaswagen) was a vehicle equipped as a mobile gas chamber. The vehicle had an air-tight compartment for victims, into which exhaust fumes were transmitted while the engine was running. The victims were gassed with carbon monoxide, resulting in death by monoxide poisoning and suffocation. The gas van was invented and used by the Soviet secret police NKVD in the late 1930s during the Great Purge. It was later widely implemented as an extermination method in Nazi Germany to kill those the regime deemed enemies of the state, mostly Jews.
The gas van was invented in the Soviet Union in 1936, by Isay Berg, the head of the administrative and economic department of the NKVD of Moscow Oblast which suffocated batches of prisoners with engine fumes in a camouflaged bread van while on the drive out to the mass graves at Butovo, where the prisoners were subsequently buried. According to Aleksandr Solzhenitsyn.
The fact of the invention of the gas chamber by Berg is not documented, but it is only a version of the authors published in literary (non-documentary) literature.
I. D. Berg was ordered to carry out the decisions of the NKVD troika of Moscow Oblast, and Berg was decently carrying out this assignment: he was driving people to the executions by shooting. But, when in Moscow Oblast there came to be three troikas having their sessions simultaneously, the executioners could not cope with the load. They hit upon a solution: to strip the victims naked, to tie them up, plug their mouths and throw them into a closed truck, disguised from the outside as a bread van. During transportation the fuel gases went into the truck, and when delivered to the farthest [execution] ditch the arrestees were already dead."