Air is made up of oxygen, nitrogen and carbon dioxide. It consists of approximately 78 percent nitrogen, 20 percent oxygen and trace amounts of carbon dioxide.
The lungs absorb oxygen and deliver it via the blood to all of the body's cells. Living things cannot breathe in pure oxygen for a long time without experiencing toxicity. The body's cells do not use nitrogen even though it does go into the blood after inhalation. In the body, this element is within the DNA, RNA and different proteins in the body. Carbon dioxide is a waste gas that the body excretes with exhalation.