Exhaled air contains primarily which gas?

• A. Oxygen
• B. Carbon Dioxide
• C. Nitrogen
• D. Argon

Answer: (B)

Gas exchange in the lungs changes the amounts of gases but not the order of abundance. The air you exhale still contains mostly nitrogen, with oxygen levels lower than what you inhaled and carbon dioxide higher because it’s the waste product of metabolism. Nitrogen is not absorbed by the lungs, so it remains the largest component in exhaled air. In other words, while carbon dioxide is present and increased compared to inhaled air, it is not the majority; nitrogen still makes up most of the exhaled gas.