The gas emitted from the lungs during exhalation is primarily carbon dioxide (CO2). During the process of respiration, oxygen is inhaled into the lungs and transported to the bloodstream, where it is utilized by cells for metabolic processes. As a byproduct of these metabolic processes, carbon dioxide is produced and carried back to the lungs via the bloodstream. When a person exhales, this CO2 is expelled from the body, allowing for the removal of waste gases and the maintenance of the body's internal balance of gases. This exchange is essential for sustaining life, as it helps regulate pH levels in the bloodstream.