How long does it take to lose consciousness without airplane pressure?

Several minutes: Airplanes are pressurized to keep you relatively comfortable: set to alttudes between 6, 500 and 8, 000 ft. Sudden decompression while flying at altitudes of 30, 000 ft is an emergency. It is very cold and the oxygen level is very low. You will pass out within a few minutes due to low oxygen, that is why the plane is equipted with emergency oxygen masks.