What is the maximum depth on air without exceeding a PPO2 of 1.26 ata?

To determine the maximum depth on air without exceeding a partial pressure of oxygen (PPO2) of 1.26 ata, it's important to understand the relationship between depth, pressure, and oxygen percentages. Air consists of approximately 21% oxygen, and as a diver descends, the pressure increases, which also affects the PPO2 of the gas they are breathing.

At sea level, the absolute pressure is 1 atm (equivalent to 33 feet of seawater, fsw). The total pressure increases by approximately 1 ata for every 33 feet of seawater as a diver descends. To calculate the depth at which the PPO2 reaches 1.26 ata, the following steps are taken:

1. The formula to calculate the PPO2 is:

( \text{PPO2} = \text{Total Pressure} \times 0.21 ).

2. Rearranging this gives you the total pressure as:

( \text{Total Pressure} = \frac{\text{PPO2}}{0.21} ).

3. Substituting the maximum allowable PPO2 of 1.26 ata into the formula gives:

( \text{Total Pressure} = \frac