What aspect must divers monitor always when using nitrox?

When using nitrox, divers must consistently monitor both depth and ascent rate to ensure safety during their dives. This is primarily because nitrox has an elevated oxygen content compared to air, which affects the maximum operating depth and limits exposure to partial pressure of oxygen.

Maintaining the correct depth is essential; if a diver exceeds the maximum recommended depth for the specific nitrox mix they are using, they risk oxygen toxicity, which can have severe consequences. Moreover, monitoring ascent rate is critical for preventing decompression sickness. An appropriate ascent rate allows for the safe elimination of nitrogen from the body, particularly when using mixed gases like nitrox, as the nitrogen washout dynamics can differ from standard air diving.

While factors like air supply, personal enjoyment, and environmental conditions are also important to consider during dives, they do not carry the same critical implications for immediate safety and physiological effects as depth and ascent rate do when diving with nitrox.