Gas chamber and crematorium:

A former ammunition bunker that was a little off, was converted into a crematorium. There also executions were carried out by the Gestapo court martial for Upper Silesia. In the summer of 1941, a ventilation system was installed. Rooms of the crematorium were converted into a gas chamber by proposed several holes in the ceiling. There, 900 Soviet prisoners of war were killed with the insecticide Zyklon B in December 1941 in an action. Also proven is the gasification 400 Incapacitated Jewish forced laborers who were brought in February 1942 from Upper Silesia there. This first and only gas chamber in the main camp was used only until May 1942.

The crematorium itself was in operation until the end of July 1943. Its capacity was not sufficient to after replacement. After the resulting construction documents for the expansion of the main camp in June 1941 and February 1942, it planned to build a new larger crematorium in Auschwitz I. But the order dated October 1941 for five three-muffle ovens at the company JA Topf and Sons was canceled in February 1942; the furnaces were needed for Crematorium II at Auschwitz-Birkenau. The "old crematorium" (or cream. I) was converted into an air raid shelter for the SS guards. The openings were sealed for the pouring of Zyklon B with concrete.

After the war, the Polish authorities made these tags reversed to create a museum visual object. In effect, the filler shown today were created only after 1945. From this fact, pull Holocaust deniers one of their most popular arguments. According to testimony of the time involved in dismantling Poland Adam Zlobnicki the subsequently covered with concrete openings were clearly visible. Photos from the period before the reconstruction demonstrate this point.

It is believed that a total of up to 36000 dead were cremated in the crematorium of Auschwitz. The number of gassed victims at this location is only a small fraction of that.

source: http://de.wikipedia.org/wiki/KZ_Auschwitz_I_(Stammlager)