What the capillaries in the air sacs give off?

The capillaries in the air sacs, or alveoli, give off carbon dioxide and take up oxygen during the process of gas exchange. Oxygen from the inhaled air diffuses into the blood in the capillaries, while carbon dioxide, a waste product of metabolism, diffuses from the blood into the alveoli to be exhaled. This exchange is essential for maintaining the body's oxygen levels and removing CO2.