Carbon dioxide is central to the processes of life on earth.

Carbon dioxide is present in the atmosphere at about 400ppm or about 0.04%.

Eucapnia is the state of having a normal healthy concentration of carbon dioxide in the blood.

Excessive carbon dioxide in the blood is hypercapnia and too little is called hypocapnia.

There are three ways that the amount of carbon dioxide is regulated in our bodies:

1. cellular respiration

2. effective transport in the blood

3. effective ventilation