Partial Pressure
Definition
Partial pressure refers to the pressure exerted by a single gas within a gas mixture, important for understanding gas absorption in diving.
More on Partial Pressure
In diving, partial pressure is calculated by multiplying the fraction of a gas by the ambient pressure. For example, oxygen at 21% in air at 30 meters (4 ATA) has a partial pressure of 0.84 ATA. Partial pressure helps determine how much gas is absorbed into the body, especially nitrogen and oxygen. It is central to understanding decompression theory, nitrogen narcosis, and oxygen toxicity. Dive computers use partial pressure calculations to assess risk and track gas exposure.
Frequently Asked Questions
Multiply the gas percentage (as a decimal) by ambient pressure in ATA. For 32% oxygen at 3 ATA, PPO₂ = 0.32 × 3 = 0.96 ATA.
It determines gas absorption in tissues, affecting decompression, narcosis, and oxygen exposure limits.
For recreational diving, a maximum of 1.4 ATA is used; 1.6 ATA is considered the contingency ceiling.
As you descend, ambient pressure increases and so does the partial pressure of each gas in your breathing mix.
Yes. Even on air, increasing nitrogen partial pressure can contribute to narcosis or decompression issues.