Which term is the amount of air in the lungs after completely exhaling?

• A. Inspiratory Reserve Volume
• B. Residual Volume
• C. Tidal Volume
• D. Dead Space

Answer: (B)

The amount of air left in the lungs after a complete exhale is residual volume. This volume remains in the lungs to keep the airways open and to prevent the alveoli from collapsing between breaths, ensuring some gas exchange can continue even when you’re not actively inhaling. It’s different from tidal volume, which is the normal amount of air moved in and out during quiet breathing; inspiratory reserve volume is the extra air you can inhale beyond a normal breath, and dead space refers to air in the conducting airways that doesn’t participate in gas exchange. In a typical adult, residual volume is about 1,200 mL, though it varies, and it isn’t measured with standard spirometry.