A normal resting breath increases lung volume by approximately 20% (500ml), maintaining blood oxygen levels from 40 mmHg to 100 mmHg.

“At rest the volume of air in your lungs is about 2 and 1/2 lers. When you take a breath you're taking another 500 milliliters or half a liter. That's the size maybe a little of my fist. So you're increasing the volume by 20%. But you're you're doing that by pulling on this 70 square meter membrane, but that's enough to bring enough fresh air into the lung to mix in with the air that's already there that the oxygen levels in your your bloodstream goes from a partial pressure of oxygen, which is 40 mm of mercury to 100 millm of mercury.”