How is the Maximum Operating Depth (MOD) determined for Nitrox mixtures?

The Maximum Operating Depth (MOD) for Nitrox mixtures is determined by analyzing the oxygen percentage within the mixture. This is crucial because the partial pressure of oxygen increases with depth, and exceeding certain levels can lead to oxygen toxicity, which can have serious physiological effects.

To find the MOD, you can use the formula: MOD (in feet or meters) = (Maximum PPO2 / Fraction of Oxygen) - 1. For example, if a Nitrox mix contains 32% oxygen, the maximum partial pressure of oxygen is typically set at 1.4 ATA for recreational diving, leading to a calculated MOD that indicates the safe depth limit for diving with that specific gas mixture. Understanding this relationship helps divers avoid dangerous situations by ensuring they do not exceed the safe operating limits of the Nitrox mixture they are using.

Other methods listed do not directly determine the MOD; for instance, regulator specifications relate to equipment use rather than gas mixture properties, and environmental factors or dive duration do not specifically dictate the mix's safe depth.