High Altitude Hypoxia & TUC Calculator

Time of useful consciousness is how long a person can think and act effectively after losing their oxygen supply at altitude. It shortens rapidly with height because the air pressure, and so the oxygen available, falls. Commonly published figures are about 3 to 5 minutes at 25,000 ft and 30 to 60 seconds at 35,000 ft, with only seconds at the highest levels. A rapid decompression shortens these times because the lungs are emptied of oxygen quickly. Individuals vary with fitness, smoking and activity. Hypoxia can be subtle: euphoria, tunnel vision and poor judgement come first. The figures are for education, so always follow your aircraft's oxygen procedures and training.