The gas produced by the human respiratory system is carbon dioxide (CO2). When we inhale, our bodies take in oxygen, which is used for cellular respiration to produce energy. During this process, carbon dioxide is generated as a byproduct and transported back to the lungs via the bloodstream. Upon exhalation, this carbon dioxide is released into the atmosphere. The balance of oxygen intake and carbon dioxide output is crucial for maintaining the body's homeostasis. The respiratory system's efficiency in exchanging gases is vital for overall health and proper functioning of the body's systems.