What is the maximum partial pressure of oxygen recommended for Nitrox diving?

The maximum partial pressure of oxygen recommended for Nitrox diving is 1.4 ATA (atmospheres absolute). This level is considered optimal for recreational diving because it provides a balance between maximizing the benefits of increased oxygen in the breathing gas while minimizing the risk of oxygen toxicity.

Oxygen toxicity can start to become a concern at partial pressures above 1.4 ATA, particularly in terms of central nervous system effects, which can include symptoms such as visual disturbances, nausea, dizziness, and potentially severe neurological events in extreme cases. The selection of 1.4 ATA allows divers to take advantage of the benefits of breathing Nitrox — such as reduced nitrogen absorption and extended bottom times — while keeping safety as a priority.

While some allow for a maximum of 1.6 ATA in specific circumstances or advanced training, it is generally not recommended for recreational divers due to the increased risk associated with that level. Thus, 1.4 ATA is the most widely accepted maximum limit for safe Nitrox diving.