Final answer:
The term used to denote the air that remains in the respiratory system after maximal exhalation is the residual volume (RV).
Step-by-step explanation:
The term used to describe the minimum amount of air always present in the respiratory system after blowing out all you can is known as residual volume (RV). Residual volume is the volume of air left in the lungs after an individual has exhaled as much as they physically can. It is essential because it prevents the alveoli, the tiny air sacs in the lungs where gas exchange occurs, from collapsing and ensures that there is a consistent supply of oxygen so that large fluctuations in respiratory gases are avoided. Unlike the tidal volume (TV), inspiratory reserve volume (IRV), and the expiratory reserve volume (ERV), the residual volume cannot be expelled from the lungs; it is always present, making continuous breathing possible.