Which gas percentage is important for determining Nitrox's maximum operating depth?

The oxygen percentage is crucial for determining Nitrox's maximum operating depth because it directly impacts the maximum allowable exposure a diver can have to oxygen under pressure. As divers descend, the partial pressure of oxygen in the breathing gas increases due to the increase in ambient pressure. Each breathing gas mix, including Nitrox mixtures, has a maximum partial pressure of oxygen that is considered safe. This limit is usually set at 1.4 to 1.6 ATA (atmospheres absolute) for recreational diving.

When using Nitrox, divers must calculate the maximum operating depth (MOD) to ensure that the partial pressure of oxygen does not exceed this safe limit. The MOD is determined by the percentage of oxygen in the mixture and involves the use of a simple formula: MOD = (maximum partial pressure of oxygen) / (fractional percentage of oxygen in the mix) - 1. This calculation helps divers to stay within safe limits and minimize the risk of oxygen toxicity during the dive.

In contrast, while other gas percentages like nitrogen's are relevant for considerations such as dive time and no-decompression limits, the determination of MOD is specifically governed by the oxygen content in the gas mix. Therefore, the oxygen percentage is the key factor in ensuring a safe diving environment