What does the term "oxygen clock" refer to in Nitrox diving?

The term "oxygen clock" in Nitrox diving specifically refers to the time spent at a certain depth under a specific partial pressure of oxygen (PPO2) level that can lead to oxygen toxicity. This concept is crucial for divers who use Nitrox, as varying mixtures of oxygen can alter the thresholds for safe exposure times.

When divers go deeper or breathe gases with higher oxygen content, the risk of oxygen toxicity increases, and understanding the "oxygen clock" allows divers to monitor their exposure and manage their time underwater effectively. By keeping track of the duration spent at specific depths with higher PPO2 levels, divers can make informed decisions about their dive profiles and necessary safety precautions, such as performing appropriate safety stops or adhering to no-decompression limits.

This relationship between depth, PPO2, and time is essential for preventing toxic effects, such as central nervous system oxygen toxicity, which can impair function and lead to serious diving accidents.