Given below are the difference between the IRV and ERV are given below:      IRV  :   Total lung capacity minus the volume of air in the lung at the end of a normal inspiration. This means that we have a reserve volume that we can tap into as tidal volume increases with exercise or activity.   IRV is about 2500 – 3500 mL in the human lungs.      ERV  :   Difference between the volume of air left in the lung at the conclusion of normal expiration versus at the conclusion of maximal expiration. That means that we have a "reserve" volume which we can tap into when our tidal volume increases with exercise or activity.   ERV is about 1000 – 1500 mL in the human lungs.