Abstract: An animal is stunned before being slaughtered by first being enclosed in a chamber that is then evacuated to an intermediate pressure well below the normal high pressure the animal is used to until the animal loses consciousness but not reflexes. Then the chamber is evacuated again to a low pressure well below the intermediate pressure and this very low pressure is maintained until the animal is without reflexes. The two evacuation steps each take place in less than about 5 sec and together they take about 7 sec. The low pressure is held for about 30 sec. The intermediate pressure can be for a pig about 150 mbar and the low final pressure about 30 mbar.