Tidal volume is the volume of air taken into the lungs with each resting breath and is about 0.5dm3 in adults.Vital capacity is the maximum volume of air that can be breathed out after the deepest possible breath in.Inspiratory reserve volume is the extra amount of air that can be breathed in above the normal tidal volume.Expiratory reserve volume is the extra amount of air forced out of the lungs above the normal tidal volume breathed out.Residual volume is the volume left in the lungs when a person exhales as hard as possible.