What is the primary concern when using enriched air nitrox for diving?

When using enriched air nitrox for diving, the primary concern is oxygen toxicity. This is related to the increased concentrations of oxygen in the breathing gas compared to regular air, which contains approximately 21% oxygen. Enriched air nitrox typically contains a higher percentage of oxygen, often between 32% to 36%.

At heightened ambient pressures, which divers experience as they descend underwater, the partial pressure of oxygen also increases. If this partial pressure exceeds safe levels (greater than 1.4 ATA or 1.6 ATA, depending on the diver's exposure and depth), it can lead to oxygen toxicity, which manifests in a range of symptoms, including vision changes, seizures, and other neurological effects. Thus, understanding the limits of oxygen exposure is crucial for safe diving with nitrox.

Other concerns like carbon dioxide retention and hypoxia are relevant but are typically secondary to the risks associated with oxygen toxicity in the context of enriched air nitrox. Hypothermia can occur in diving situations but is not specific to the use of nitrox itself and is more associated with the water temperature and exposure time rather than the gas composition being breathed.