The process of moving air into the lungs is called inhalation. Most people inhale and exhale (moving air out of the lungs) approximately 20,000 times per day. With each inhaled breath, air moves in through the nostrils or mouth and travels down the trachea into the lungs.
The primary job of the lungs is to move oxygen into the body and carbon dioxide out. Humans cannot survive without oxygen, and the lungs absorb this necessary gas. Once the oxygen is inside the lungs, it moves into the bloodstream, which transports the oxygen all over the body. As cells use the vital oxygen, they release a waste product called carbon dioxide. This toxic gas replaces oxygen in the bloodstream and moves back to the lungs for exhalation.