The Importance of Oxygen to Sustain Life

The Human body is dependent on oxygen. As the altitude increases, the consequent decrease in pressure reduces the amount of oxygen the human body can absorb when breathing. To enable flight at high altitudes either the aircraft cabin has to be pressurised, to replicate the pressure at a lower altitude, or the occupants of the aircraft have to be given supplemental oxygen. At the cruising levels commonly flown by commercial air transport aircraft, loss of pressurisation can quickly lead to incapacitation. The higher the altitude, the lower the Time of Useful Consciousness: