To ensure safety, what should divers be aware of regarding ppO2 changes during ascent?

Understanding the behavior of partial pressure of oxygen (ppO2) during ascent is crucial for diver safety. As a diver ascends, the surrounding water pressure decreases, which directly affects the ppO2 experienced by the diver. Since ppO2 is determined by both the concentration of oxygen in the breathing gas and the surrounding pressure, as the diver rises to shallower depths, the overall pressure decreases and consequently the ppO2 also drops.

With this in mind, being aware that ppO2 decreases rapidly during ascent is essential since it helps divers manage their breathing gas and monitor for potential hypoxia. Hypoxia occurs when there is insufficient oxygen available to breathe, which can be exacerbated if a diver is utilizing high-oxygen content mixes like Nitrox. Therefore, recognizing this rapid change in ppO2 assists in maintaining safe breathing practices and helps prevent oxygen toxicity or other complications associated with improper gas management during an ascent.