Using the MOD calculation, what is the maximum operating depth for a Nitrox blend of EAN32?

To determine the maximum operating depth (MOD) for a Nitrox blend of EAN32, you need to consider the oxygen content in the mix and the depth at which partial pressures of oxygen (PPO2) become unsafe.

EAN32 consists of 32% oxygen and 68% nitrogen. The safe maximum PPO2 for recreational diving is typically set at 1.4 ATA, which is equivalent to 1.4 times the atmospheric pressure. At sea level, atmospheric pressure is approximately 1 ATA, and for every 33 feet of seawater (fsw), the pressure increases by about 1 ATA. Therefore, to calculate the MOD, you would use the following formula:

1. Convert the percentage of oxygen to a decimal: 32% oxygen is 0.32.

2. Use the formula: MOD (fsw) = (PPO2 / 0.32) - 1 ATA, then convert that into feet of seawater.

In this instance, to find the MOD:

1. Calculate the depth at which PPO2 equals 1.4 ATA:

• 1.4 = (Depth in fsw / 33) + 1, thus