The primary gas produced by the human body when exhaling is carbon dioxide (CO2). During the process of cellular respiration, cells use oxygen to convert glucose into energy, producing carbon dioxide as a byproduct. This CO2 is then transported in the bloodstream to the lungs, where it is expelled when we exhale. Maintaining the proper balance of oxygen and carbon dioxide is essential for our respiratory system and overall bodily functions. The body regulates breathing to ensure that we take in enough oxygen while removing the excess carbon dioxide to maintain healthy levels in the blood.