State the volume of air remaining in the lungs after a normal breathing.

The volume of air remaining in the lungs after a normal, passive exhalation is called the functional residual capacity (FRC)

• FRC comprises the expiratory reserve volume (ERV) plus the residual volume (RV)

In healthy adults, FRC typically measures approximately 1800–2500 mL, with a commonly cited average value of around 2400 mL

• Some sources specify a standard value near 2300 mL

This remaining air:

• Prevents alveolar collapse

• Maintains relatively stable gas composition in alveoli between breaths

Therefore, after a normal tidal exhalation, the lungs still retain roughly 2.3–2.5 L of air at rest.