What you should know about lung disease in fire fighters
The normal human pulmonary system is made up of a number of components which work together to provide oxygen to the blood stream which is delivered to vital organs and remove waste products including CO2. The system includes the diaphragm, a muscle which through it's downward movement increases the size of the pleural (lung) space, allowing inhalation. As the diaphragm relaxes, air is passively expired as shown in the picture below.
Inhaled air passes through the mouth and pharynx, travels down the trachea which divides into the right and left bronchi (upper airways), reaching the bronchioles and then the alveoli (distal airways). The alveoli are actually tiny air sacs which expand and contact like small balloons. Each alveolus has an arterial and venous blood supply, allowing "off-gassing" of waste gases including carbon dioxide - CO2 and "on-gassing" of oxygen - O2 necessary to sustain the body's organs.