What aspect is critical in calculating the maximum operating depth for enriched air nitrox?

The critical aspect in calculating the maximum operating depth for enriched air nitrox is the partial pressure of oxygen. When using enriched air, which typically has a higher percentage of oxygen than regular air, it's essential to monitor the partial pressure of oxygen to avoid toxicity. As a diver goes deeper, the pressure increases, which subsequently raises the partial pressure of the gases the diver breathes.

The maximum operating depth is determined based on the oxygen content of the nitrox blend being used. Most guidelines suggest a maximum partial pressure of oxygen of 1.4 ATA (atmospheres absolute) to reduce the risk of central nervous system toxicity. Therefore, by knowing the composition of the nitrox and applying this partial pressure limit at depth, divers can calculate the maximum depth at which it is safe to dive.

Other aspects, such as water salinity, the partial pressure of nitrogen, and current underwater visibility do not directly affect the calculation of the maximum operating depth related to enriched air. While these factors may influence diving safety or conditions, they are not involved in determining limitations based on oxygen exposure in enriched air mixtures.