What is the primary concern of using Nitrox at greater depths?

Using Nitrox at greater depths raises the primary concern of oxygen toxicity due to the increased partial pressure of oxygen at depth. As divers descend, the pressure around them increases, which affects the gases they breathe. Since Nitrox is a blend of nitrogen and oxygen, the amount of oxygen in the mix becomes more significant as depth increases.

When diving with Nitrox, especially mixtures with higher oxygen percentages (like EANx32 or EANx36), it is essential to monitor the depth carefully. The increased pressure can elevate the partial pressure of oxygen in the diver's lungs, which can lead to toxic effects, including seizures and other serious health issues, if the partial pressure exceeds safe limits. Understanding these risks and managing the depth accordingly is vital for safe diving practices and helps divers make informed choices about their gas mixtures and dive profiles.

The other options, while they may be concerns in diving, do not pose the same specific danger related to depth as oxygen toxicity does in the context of using Nitrox.