What are the recommended limiting ppO2 values for recreational nitrox dives?

The recommended limiting partial pressures of oxygen (ppO2) values for recreational nitrox dives are set to ensure diver safety and minimize the risk of oxygen toxicity. The limits generally accepted in the diving community for recreational diving are a maximum ppO2 of 1.4 ATA during the entirety of the dive for avoiding oxygen toxicity, and a maximum of 1.6 ATA as a limit for short durations, such as in emergencies or safety stops.

Selecting a limit of 1.4 ATA allows divers to enjoy extended bottom times while reducing the risk of experiencing oxygen toxicity effects, which become more pronounced as the ppO2 increases. At the same time, allowing a maximum of 1.6 ATA offers some flexibility for brief periods without significantly increasing risk.

The other options either suggest values that do not align with established safety guidelines for recreational diving or include incorrect comparisons between partial pressure of oxygen and atmospheric conditions. Thus, the chosen answer aligns well with standard nitrox diving practices and safety protocols.