At what partial pressure of oxygen does oxygen toxicity become a concern for divers?

Oxygen toxicity is a significant concern for divers, particularly when diving with enriched air nitrox, as it can have serious physiological effects. The threshold for potential oxygen toxicity is generally considered to be above a partial pressure of 1.4 ATA (atmospheres absolute). At this level, divers may start to experience central nervous system (CNS) oxygen toxicity, leading to symptoms such as visual or auditory disturbances, twitching, and in severe cases, convulsions. This is why diving with a partial pressure of oxygen above 1.4 ATA requires careful monitoring and management, including adherence to specific depth limits and dive planning to avoid extended exposure.

The other levels mentioned are indeed relevant in the context of diving. For instance, while a partial pressure above 1.6 ATA can lead to even more severe toxic effects, the critical concern for divers that is widely recognized and used for dive planning is the 1.4 ATA threshold. This level helps divers avoid the acute effects of oxygen toxicity while allowing for safer nitrox utilization during dives. Understanding this threshold is essential for safe dive practices and helps ensure divers can plan their dives appropriately.