Does the Air ever get used up?

The air is constantly being used. All living creatures breathe in the oxygen. The nitrogen of the air is being used by certain microbes and also by men with the help of electricity. The green plants use the Carbonic acid of the air, upon which they feed. Yet the air does not get used up as regard any of these gases. Green plants everywhere in the sunlight give off to the air a great deal of oxygen. Similarly, when animals and plants die their bodies decompose and give back to the air all the nitrogen they had originally received. Finally, the Carbon dioxide taken from the air by the plants is compensated by the carbon dioxide exhaled by all living creatures when they breathe.