What is the maximum operational depth (MOD) for a 40% nitrox mixture when limiting oxygen partial pressure to 1.4 ATA?

To determine the maximum operational depth (MOD) for a 40% nitrox mixture while limiting the oxygen partial pressure to 1.4 ATA, you first need to calculate the partial pressure of oxygen in the mix.

A 40% nitrox mixture contains 40% oxygen and 60% nitrogen. To find the MOD, you can use the equation for partial pressure:

Partial pressure of oxygen (PpO2) = (Fraction of oxygen in the mix) x (Total pressure)

In diving, total pressure at a given depth can be calculated using the formula:

Total pressure (ATA) = (Depth in feet / 33) + 1

Given that the maximum partial pressure of oxygen is set at 1.4 ATA, you can set up the equation as follows:

1.4 ATA = (0.40) x (Total pressure)

Now we can rearrange to solve for total pressure:

Total pressure = 1.4 ATA / 0.40 = 3.5 ATA

Next, we substitute the total pressure back into the equation for total pressure:

3.5 ATA = (Depth / 33) + 1

Subtracting 1 from both sides gives:

2.5 =