Gas chamber carbon monoxide as the lethal agent. Sometimes a box filled with anesthetic gas is used to anesthetize small animals for surgery or euthanasia. Gas chamber A gas chamber is an apparatus for killing humans or other animals with gas, consisting of a sealed chamber into which a poisonous or asphyxiant gas is introduced. The most commonly used poisonous agent is hydrogen cyanide; carbon dioxide and carbon monoxide have also been used. Gas chambers were used as a method of execution for condemned prisoners in the United States beginning in the 1920s and continue to be a legal execution method in
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