Underwater, the pressure increases by 1 atmosphere (ATM) every 33 feet (10 meters). As a diver descends, the pressure compresses the gas in their tank, increasing the partial pressure of the nitrogen they are breathing.
That example exposes the key limitation. To get a recreational mix like 32%, you only add a small “crack” of oxygen—typically just 200–400 psi of O2 into a nearly full tank. Precise calculations or partial pressure blending tables are essential. cracked nitrox
Therefore, a diver at 100 feet is essentially functioning with the equivalent of three martinis in their system. At 130 feet, it’s four martinis. For those unaccustomed to the pressure, this is the point where the "Cracked Nitrox" takes over, and rational decision-making goes out the window. Underwater, the pressure increases by 1 atmosphere (ATM)
The single most important rule in partial pressure blending: To get a recreational mix like 32%, you