"the gas chambers and the ovens become ordinary scenery"

 Gas chambers were first used by the Nazis in the 1930s as part of ‘Action T4’, a euthanasia programme used to kill members of the population deemed ‘undesirable’.  At this stage, carbon monoxide was used, much of the time from the exhaust fumes of designated vehicles (known as ‘gaswagen’).  Later, in the camps, hydrogen cyanide, better known by its trade name of Zyklon B, was normally used as it was viewed as more ‘efficient’.  Designated gas chambers were built, some of which could murder 2,000 people at once; at Auschwitz, it was said that 20,000 people could be killed in a single day.  Made to look like showers, victims were led into them upon their arrival at the camp on the pretext of being ‘disinfected’.  This included children, as the only people likely to be spared at this stage were adults capable of slave labour.  As the war progressed, rumours ensured that many prisoners knew what was going to happen to them.  Once inside the chamber, it could take up to twenty minutes for all the victims to die; afterwards, work units of Jewish inmates had to check the corpses for gold fillings, which would then be removed.  The bodies were then burnt, initially in deep pits until crematoria were built at the major camps.  At Auschwitz, there were five, and even these were not sufficient during April-July 1944 during the massacre of Hungarian Jews.