Why is oxygen toxicity a concern when using enriched air nitrox?

Oxygen toxicity is a significant concern when using enriched air nitrox because higher oxygen percentages can lead to toxic effects on the central nervous system (CNS). When divers breathe gas mixtures with increased oxygen levels, especially above a partial pressure threshold (generally around 1.4 ATA), the likelihood of experiencing symptoms of oxygen toxicity increases. This can manifest as visual disturbances, tinnitus, anxiety, muscle twitching, and even seizures, which can be life-threatening in a diving situation.

In enriched air nitrox, while the benefit of reduced nitrogen exposure is substantial, divers must remain aware of how the elevated oxygen levels interact with their physiology at depth. This is particularly important in the context of the dive plan, where both the depth of the dive and time spent at that depth can contribute to the risk of oxygen toxicity. Proper planning, including monitoring the partial pressure of oxygen, is essential to mitigate these risks and ensure safe diving practices.