Cells obtain energy in the combustion process, which is necessary oxygen. In the oxygen combustion process produces three end products: energy, water and carbon dioxide is completely redundant. Dispose of the body, therefore, in the process of carbon dioxide gas exchange. The system transports blood from the cells into the lungs, where the exhaust is eliminated when, at his place during the inhalation portion goes into the blood of fresh oxygen.
The process of breathing is very regular and is so efficient that the concentration of carbon dioxide not exceed the concentration which could endanger health and life. At the same time ever new supply of oxygen enables the continuity of the burning cell, with the result that they acquire the energy necessary for the proper performance of their functions.