What is the maximum allowable partial pressure of oxygen for recreational divers?

The maximum allowable partial pressure of oxygen for recreational divers is set at 1.4 ATA (atmospheres absolute). This limit is based on extensive research into the physiological effects of oxygen and the risks of oxygen toxicity. When divers breathe mixtures with elevated oxygen levels, they must be cautious about the partial pressure because higher levels can lead to central nervous system oxygen toxicity, which can result in convulsions and other serious health issues.

The limit of 1.4 ATA ensures a balance between maximizing the benefits of increased oxygen content in the breathing gas—such as reduced nitrogen absorption and extended bottom times—and minimizing the risks associated with oxygen toxicity. This level is widely accepted in the diving community, especially for recreational diving where safety is paramount.

In practice, divers use this maximum partial pressure as a guideline for choosing the appropriate gas mix and planning their dives, including how deep they can safely go while maintaining an acceptable level of risk. While some advanced or technical diving applications might allow for higher partial pressures, adhering to 1.4 ATA for recreational diving ensures untrained divers stay well within safe limits.