What is the Maximum Operating Depth (MOD) for EAN32?

The Maximum Operating Depth (MOD) for EAN32, or Enriched Air Nitrox with an oxygen content of 32%, can be calculated using the concept of partial pressure of oxygen and the effects of that pressure on the diver.

To ensure safety during dives with Nitrox, divers consider the maximum permissible partial pressure of oxygen, which is generally recommended to be no more than 1.4 ATA (atmospheres absolute) at the deepest point of the dive. At sea level, the atmospheric pressure is approximately 1 ATA. Therefore, as a diver descends, the pressure increases, thus increasing the partial pressure of oxygen in the breathing gas.

For EAN32, the ratio of oxygen in the mixture is 32%, which means that when diving to a certain depth, a diver must calculate where the partial pressure of oxygen will reach that 1.4 ATA limit. The calculation involves determining the depth at which the total pressure (the sum of atmospheric pressure and the pressure due to water) would cause the partial pressure of oxygen in EAN32 to equal 1.4 ATA.

Using the formula:

MOD = (Desired partial pressure of oxygen) / (Fraction of oxygen in the mix)

Substituting the values gives