advanced practice nurse a registered nurse having education beyond the basic nursing education and certified by a nationally recognized professional organization in a nursing specialty, or meeting other criteria established by a Board of Nursing.
Quick Answer. The air that makes up Earth's atmosphere contains 20.9 percent oxygen. This is true up to about 70,000 feet above sea level. However, above 10,000 feet, the atmosphere becomes too thin to support human life, even though its proportions do not change much. Continue Reading.
Humans exhale oxygen, carbon dioxide and nitrogen. Humans inhale these same gases, though in different proportions to exhalation; that is, oxygen is exchanged for carbon dioxide during breathing. When inhaling, humans take in approximately 21 percent oxygen, 0.04 percent carbon dioxide and 79 percent nitrogen. On exhalation, humans give off approximately 16 percent oxygen, 4 percent carbon dioxide and 79 percent nitrogen, according to the BBC; only the amount of nitrogen remains constant in the exchange. Exhaled air also contains water vapor.