What is the normal maximum operating depth for EAN32 with a PO2 of 1.4 ata?

The maximum operating depth for a specific mixture of enriched air nitrox (EAN) is determined by the partial pressure of oxygen (PO2) that divers can safely encounter. For EAN32, which contains 32% oxygen and 68% nitrogen, you need to calculate the depth at which the partial pressure of oxygen reaches the safe limit of 1.4 ata.

The partial pressure is determined by the following formula:

[ \text{PO2} = \text{Percentage of O2} \times \text{Total Pressure} ]

In this case, the total pressure at a given depth can be expressed in atmospheres. For every 10 meters of sea water (msw), the pressure increases by about 1 ata due to water and atmospheric pressure. Therefore, the total pressure at depth can be computed as:

[ \text{Total Pressure} = \text{Depth (in msw)} / 10 + 1 ]

To find the maximum operating depth, rearranging the PO2 equation we find:

[ \text{Depth} = (PO2 / \text{Percentage of O2}) - 1 ]

Substituting in the values, where PO2 is 1.4 ata and