WHAT DOES BOYLES LAW PREDICT ABOUT UNEQUAL PRESSURES?
Once again we come to all-important Boyle’s law: for a given mass of gas at a constant temperature, the product of pressure (P) and volume (V) is constant (K): P x V = K. We have already seen how, for the breath-hold diver, Boyle’s law predicts that compressible air spaces will shrink on descent and re-expand on ascent, and that the situation is different for scuba divers because compressed air is continuously inhaled. Even if the scuba and breath-hold diver go to the same depth and spend the same amount of time under water (e.g., one minute), the effects of water pressure are radically different on the two divers. Because tank air is inhaled at the ambient pressure, the scuba diver’s lungs and other compressible air spaces do not shrink. Consider that all the body’s air-containing spaces are in contact with inhaled air. At the same time, there is a natural tendency for air anywhere in the body – in the lungs, middle ears, sinuses and other spaces – to diffuse into the blood. As air is
