Now let's move on to something called the residual volume. Now even when we actually forcefully expel all that air out of the lungs, we're going to end up on this purple line right here. So if we forcefully exhale, we end up right here. And notice inside the lungs we still have a certain amount of volume of air and this is known as the residual air. So no residual volume. So no matter how hard we try to breathe out, there will always be some amount of air inside our lungs.