Atmosphere and respiration · Question 1 of 12
Approximately what proportion of the air in the lower atmosphere is oxygen?
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Answer
- A 21 %
Explanation
Dry air consists of about 78 % nitrogen, 21 % oxygen and around 1 % other gases such as argon and carbon dioxide. This proportion stays the same up to great heights. With altitude, however, the air pressure and thus the partial pressure of oxygen decrease, and that is exactly what causes oxygen deficiency.