In what situation would a diver consider oxygen toxicity?

Oxygen toxicity is primarily a concern when a diver is using enriched air nitrox, especially at partial pressures of oxygen that exceed safe limits. When using nitrox mixtures with higher oxygen content, such as those commonly used for deeper dives, the partial pressure can rise above 1.4 ATA (atmospheres absolute). This threshold is critical because it indicates a level of oxygen that increases the risk of toxicity, which can lead to symptoms such as visual disturbances, convulsions, and impaired judgment.

At partial pressures above this limit, the likelihood of experiencing central nervous system (CNS) toxicity rises significantly, making it essential for divers to monitor their depth and time spent at depth closely, especially in relation to the type of gas they are breathing.

In the context of the other scenarios, using air at high altitudes, diving deeper than 30 meters, or surfacing too quickly do involve significant risks but are not directly tied to the specific concern of oxygen toxicity related to the partial pressure of oxygen. While those situations may involve other physiological concerns, they do not specifically relate to the risks associated with elevated oxygen levels experienced with enriched air nitrox.