Shameless Fearmongering Versus Reality Forced penting capacity: the maximum amount of air you can forcibly exhale from your lungs after fully inhaling. it is about 80 percent of total capacity, or 4. 8 liters, because some air remains in your lungs after you exhale. forced vital capacity can decrease by about 0. 2 liters per decade, even for healthy people who have never smoked. Forced vital capacity: the maximum amount of air you can forcibly exhale from your lungs after fully inhaling. it is about 80 percent of total capacity, or 4. 8 liters, because some air remains in your lungs after you exhale. forced penting capacity can decrease by about 0. dua liters per decade, even for healthy people who have never smoked. liters of air (a ballpark figure for good lung capacity) down to a single liter of volume the earliest research on breath-hold diving assumed that the maximum depth of any diving was determined by the residual volume of the lungs theorists assumed that, once the pressur...