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.
Is air a pure substance? Air is not a pure substance but a mixture of different gases. It is composed of approximately 78 percent nitrogen and 21 percent oxygen, with small amounts of about a dozen other gases making up the remainder.