The primary gas released during human respiration is carbon dioxide (CO₂). When humans breathe in oxygen, it is utilized by the body’s cells to produce energy through a process called cellular respiration. In this process, glucose is broken down, and oxygen is consumed, producing carbon dioxide as a byproduct. This gas is then transported back to the lungs and expelled from the body when we exhale. Carbon dioxide plays a critical role in maintaining the body's acid-base balance and is also a vital component in the respiratory cycle, influencing the rate and depth of breathing based on the body’s metabolic needs.