The gas produced by humans during respiration is carbon dioxide (CO2). During the process of respiration, oxygen is inhaled and used by the body's cells to convert glucose into energy. This biochemical reaction generates carbon dioxide as a waste product, which is then transported back to the lungs through the bloodstream. Once in the lungs, carbon dioxide is expelled from the body when we exhale. The regulation of CO2 levels is crucial for maintaining the body's pH balance and overall homeostasis. This gas is also significant in the broader context of global warming and climate change due to its greenhouse gas properties.