What does the term “oxygen clock” refer to?

The term “oxygen clock” refers to the limit for safe exposure to oxygen at a given partial pressure. When divers use enriched air nitrox, they must be aware of the effects of oxygen toxicity, which can occur when the partial pressure of oxygen in the breathing gas exceeds certain thresholds. The "oxygen clock" effectively measures the cumulative exposure time to elevated partial pressures of oxygen, helping divers track how long they can safely be exposed to these conditions before risking toxicity.

This concept is critical in managing dive profiles and ensuring the safety of divers using enriched air. Understanding the oxygen clock allows divers to plan their dives effectively and avoid exceeding the safe limits, which is essential for preventing serious health issues.