Where does the greatest rate of pressure/volume change occur?

The greatest rate of pressure/volume change occurs between 0-33 feet or 0-10 meters of depth. This range corresponds to the transition from surface pressure to the pressure experienced at typical recreational diving depths. At sea level, the atmospheric pressure is approximately 1 atmosphere (ATA), and as a diver descends to 33 feet, the pressure increases to about 2 ATA.

The significance of this range lies in the fact that for every 10 meters (or approximately 33 feet) of seawater, the pressure increases by about 1 ATA. Consequently, in the first 33 feet of descent, the diver experiences a doubling of pressure, leading to significant changes in buoyancy and volume of gases. According to Boyle’s Law, as pressure increases, the volume of gas decreases, which becomes particularly pronounced in this initial depth range.

Understanding this pressure change is critical for divers in managing buoyancy, planning their dives, and ensuring safety regarding decompression and gas expansion during ascent. The effects of pressure changes are less dramatic at greater depths, as the incremental increases in pressure — while still significant — are not as large in proportion to the volume changes as they are in the first few meters of descent.