What is the maximum oxygen percentage allowed in EANx diving?

The maximum oxygen percentage allowed in EANx (Enriched Air Nitrox) diving is 40%. This concentration is significant because it aligns with the guidelines established for recreational diving, which stipulate a maximum of 40% oxygen to help manage the risk of oxygen toxicity and other related issues.

When using EANx, divers benefit from reduced nitrogen levels in the gas mix, which allows for longer bottom times and shorter surface intervals compared to standard air. However, oxygen toxicity becomes a concern at higher partial pressures, making it crucial to adhere to the upper limit of 40%. At this level, divers can safely dive within the recommended depth limits and enjoy the advantages of enriched air without entering a zone where oxygen toxicity poses significant risks.

The other options present lower concentrations of oxygen than the maximum permissible level. These lesser percentages would be considered safe but do not allow divers to fully utilize the benefits associated with EANx diving.