What is the single most important aspect of managing your exposure to oxygen when diving?

Determining a maximum operating depth (MOD) based on a limiting partial pressure of oxygen (ppO2) of 1.4 bar or less is indeed the single most crucial aspect of managing oxygen exposure while diving. The reason for this is rooted in the physiological effects of oxygen on the human body, particularly in relation to oxygen toxicity and safe diving practices.

When divers descend, the partial pressure of oxygen within the breathing gas increases with depth. Maintaining a ppO2 that does not exceed 1.4 bar helps to mitigate the risks of oxygen toxicity, which can manifest as symptoms ranging from visual disturbances and seizures to serious neurological effects. Setting the MOD ensures divers operate within a safe range that enhances safety during dives, particularly when combined with the principles of dive planning and adherence to safe ascent rates.

While factors such as tracking the depth of previous dives and considering maximum operating depths based on higher ppO2 or fractions of oxygen are important, they don't prioritize the critical need for safe oxygen exposure as effectively as adhering to a limit of 1.4 bar. This specific threshold has been well established through research and diving practice, making it a fundamental aspect of safe nitrox diving.