The systematic murdering of humans through gas during the Nazi rule was introduced for the first time from January 1940 on in the area of the "Euthanasia," the extermination of the "lives not worthy to live" of the handicapped, mental patients and the terminally ill, and from fall 1941 on was continued to a much larger extent by the pogroms of the operation groups of the security police and the SD in the seized eastern areas with the help of mobile gas vans.
Beginning December of 1941 one proceeded in the camp Kulmhof (Polish Chelmno) to use stationary gas vans for the killing of Jews, and from the beginning of 1942 in different camps fixed gas chambers were built, or already existing buildings were restructured for this purpose.
One needs to differentiate by the furnishing of such gas chambers and the gassing actions carried out within them between the mass gassings of Jews in the extermination camps build for that purpose and the gassings of smaller scale in individual, already existing concentration camps (whereby patients, seized forced laborers, war prisoners, and political prisoners among others were also victims)
The following extermination camps existed in Poland:
Chelmno: Located in the then-Wartheland. Between December 1941 and fall 1942 and again from May until August 1944 gassings by means of carbon monoxide from motor exhaust gas took place. Altogether more than 150,000 Jews as well as 5000 gypsies have hereby been killed.
Belzec: Located in the Lublin district. From march to December 1942 in the beginning in three, later in six large gas chambers by means of carbon monoxide from motor exhaust gas altogether about 600,000 Jews were killed here.
Sobibor: Located in the Lublin district. Received three gas chambers in April 1942 three and later another three in September 1942 and until October 1943 it was "in operation". During this period at least 200,000 Jews have been murdered through carbon monoxide gas.
Treblinka: Located in Warschau district. From the end of July 1942 on had three gas chambers and received at the start of September 1942 furthermore ten larger gas chambers. Up to the dissolution of the camp in November 1943 altogether 700,000 Jews were killed here by carbon monoxide.
Majdanek: Located in the Lublin district. The concentration camp existing since September 1941 turned into an extermination camp when between April 1942 and November 1943 mass shootings took place to which 24,000 Jews fell victim. In October 1942 also two, later three gas chambers were built. In the beginning the killings in these were done by means of carbon monoxide, soon however one was using Zyklon B (a highly poisonous insecticide made from cyan hydrogen). Up until the dissolution of the camp in March 1944 about 50,000 Jews have been gassed.
Auschwitz-Birkenau: Located in the formerly polish, upper eastern Silesian area south eastern of Kattowitz. The extermination camp in Birkenau, established in the second half of 1941, was joined to the concentration camp Auschwitz, existing since May 1940. From January 1942 on in five gas chambers and from the end of June 1943 in four additional large gassing-rooms gassings with Zyklon B have been undertaken. Up until November 1944 more than one million Jews and at least 4,000 gypsies have been murdered by gas.
In the following concentration camps gas chambers were established and were in operation during the Holocaust:
Mauthausen (upper Austria): From fall 1941 on one gas chamber existed which was operated with Zyklon B. In addition, gassings with carbon monoxide took place through gas vans which were driven between Mauthausen and it's side-camp Gusen. Altogether more than 4000 have been killed here through gas.
Neuengamme (southeastern of Hamburg): From fall of 1942 on gassings with Zyklon B were undertaken here in a "Bunker" prepared for that, about 450 victims.
Sachsenhausen (Province Brandenburg, north of Berlin) received mid March 1943 a gas chamber which was operated with Zyklon B. Several thousand people fell victim to the gassings, a more specific number cannot be determined.
Natzweiler (by Struthof, Elsass): From August 1943 to August 1944 a gas chamber existed here in which between 120 and 200 people were killed through Zyklon B in order to be able to dissect their skeletons for the Anatomica Institute of University of Strassburg. Back then this institute was managed by a chief company commander of SS Prof. Dr. August Hirt.
Stutthof (east of Danzig) had from June 1944 on one gas chamber in which more than 1000 were killed by Zyklon B.
Ravensbruck (Bradenburg, north of Berlin): Here still in January 1945 a gas chamber was established; the number of the people killed in it was at least 2,300.
Dachau (Upper Bavaria, northeast of Munich): During the establishment of a new house of cremation in 1942 also a gas chamber was established in it in which in connection with the medical experiments of the chief company commander of SS Dr. Rascher also a few experimental gassings were undertaken, as more recent research has confirmed. (On that see Gunther Kimmel: The Concentration Camp Dachau. A study of the Nazi crimes of violence in Bavaria in the NS-time II, edited by Martin Broszat and Elke Froehlich, Munich, R. Oldenburg Press, 1979, P. 391.) Larger gassing operations have not taken place in Dachau.
The victims of the operation groups of the security service and the SD behind the German frontier in the Russia-campaign were to the by far largest part Jews. Their number is estimated to be at least 900,000.
The difference between the total of the victims of the gassings cited in the above mentioned composition and the number of victims of the operation groups and the total of roughly 6 million victims of the Nazi persecution of the Jews results from the fact that a very high percentage of the victims have lost their lives through indirect extermination actions such as the method "destruction through work," bad treatment, under nourishment, epidemics, exhaustion during forced transportations etc.
About 120,000 people were killed through the Nazi "Euthanasia" actions.
Sources:The Institut Fuer Zeitgeschicthe (Institute for Contemporary History) in Munich, Germany, 1992.