Pulmonary air volumes and capacities:

1. Tidal volume: volume of air inspired or expired in a normal Respiration, 500ml.
2. Inspiratory reserve volume: it is the extra amount of air which can be inhaled forcibly after a normal inspiration. 2000 to 2500 ml.
3. Expiration reserve volume: it is the extra amount of air which can be exhaled forcibly after a normal expiration. 1000 to 1500 ml. 
4. Vital capacity of Lungs: Total amount of air which can be exhaled and inhaled with maximum efforts.

TV + IRV + ERV 500 + 2000 + 1500 4000 approx.

5. Residual volume: The volume of air remains in lungs even after a forcible expiration. 1500 ml approx.
6. Inspiratory capacity: Total volume which can be inhaled after a normal expiration. (Tidal volume + IRV) = 500 + 2000 = 2500ml.
7. Expiratory capacity: Total volume which can be exhaled after a normal inspiration. (Tidal volume +ERV) = 500 + 1000 = 1500 - (2000) approx.
8. Total lung capacity (TLC): Vital capacity +residual volume

= VC + RV

= (TV + IRV + ERV) + RV

= (500 + 2000 + 1500) + 1500

= 5000 – 6000 ml approx.

       i) Spirometer or respirometer: An instrument that measures the charges in the movement of air in and out of lungs.