What does the Maximum Operating Depth (MOD) depend on when diving with nitrox?

When diving with nitrox, the Maximum Operating Depth (MOD) is primarily determined by the partial pressure of oxygen (ppO2). Nitrox blends contain a higher concentration of oxygen compared to air, which increases the risk of oxygen toxicity if the ppO2 exceeds safe limits. For recreational diving, the commonly accepted limit for the ppO2 is 1.4 ata, which helps ensure diver safety.

Calculating the MOD involves using the percentage of oxygen in the gas mix to determine the maximum depth at which the oxygen level remains within this safe limit. As a diver descends, the pressure increases, and so does the ppO2; therefore, adhering to this limiting factor is essential for safe diving practices when using enriched air nitrox.

The other factors listed, such as water temperature or equipment maximum operating pressure, do not directly determine the MOD related to the use of nitrox. Similarly, while bodily tolerance to nitrogen is important for understanding narcosis and decompression limits, it does not influence the MOD that safeguards against oxygen toxicity while using nitrox.