03. At what distance from Earth do we have to start using oxygen? (RR) (A K2S Question)

From The Space Library

The early signs of hypoxia generally begin at 10,000 feet. US Air Force aircrews must use supplemental oxygen when the cabin pressure of the aircraft reaches this altitude. The atmosphere is generally considered to exist up to 100,000 feet; above this altitude the atmosphere is virtually a vacuum until reaching outer space. One-half of the atmosphere is contained from 18,000 feet to the Earth's surface; the other half is from 18,000 feet to 100,000 feet. Hypoxia is the effect of an insufficient supply of oxygen to the body. Every person can have different symptoms when suffering from hypoxia; in fact, US Air Force aircrews are required to take an altitude chamber ride every three years to reinforce and identify their hypoxic symptoms. Some of the common symptoms are feeling lightheaded or dizzy, experiencing reduced vision, and feeling euphoric.

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Answer provided by Lonnie Moffitt & Russell Romanella

Question and Answer extracted from the book Kids to Space - by Lonnie Schorer

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