What is the partial pressure of O2 in air at 158 fsw?

To determine the partial pressure of oxygen (O2) at a specific depth in the water, one must consider both the atmospheric pressure and the depth's pressure contribution. At sea level, the atmospheric pressure is approximately 14.7 psi, and for every 33 feet of seawater (fsw), the pressure increases by approximately 1 atmosphere (ata) or about 14.7 psi.

At 158 fsw, we first calculate the total pressure. The depth contributes pressure as follows:

1. Atmospheric pressure at sea level: approximately 14.7 psi.

2. Pressure due to the water above at 158 fsw: 158 fsw / 33 fsw per ata ≈ 4.79 ata, which translates to roughly 4.79 atmospheres of pressure.

Converting this back to psi:

• Total pressure at 158 fsw = Atmospheric pressure + Water pressure

• Total pressure = 14.7 psi + (158 fsw * 0.445 psi/fsw) ≈ 14.7 psi + 70.3 psi = 85 psi (This is just an illustrative calculation; we focus on the context.)

In terms of oxygen's contribution, since air is composed of about