Breathing is the source of life: if breathing stops, do does life. On average, an adult breathe 16-18 times per minutes, each time about 500ml of air exchanged in the lungs. When breathing in from the outside air, oxygen content is about 21% while carbon dioxide is 0.03%. On the other hand, breathing out produces about 16.5% oxygen and 4.5% carbon dioxide.

Based on the average of 16-18 breath per minutes, it can be estimated that the volume of air exchanged in the lungs is about 8000-9000ml. From this, the content of both oxygen and carbon dioxide exchanged can also be calculated.

In calculating the air exchanged, there