Zyklon B
Once the door of the filled gas chamber was sealed, pellets of Zyklon B were dropped through special holes in the roof. Regulations required that the Camp Commandant supervise the preparations, the gassing (through a peephole), and the aftermath looting of the corpses. Commandant Höss reported that the gassed victims "showed no signs of convulsion"; the Auschwitz camp physicians attributed that to the "paralyzing effect on the lungs" of the Zyklon-B gas, which killed "before" the victim began suffering convulsions.