What is the maximum recommended oxygen percentage in recreational Nitrox?

The maximum recommended oxygen percentage in recreational Nitrox is 40%. When divers use Nitrox, they typically choose mixtures with higher oxygen concentrations than standard air, primarily to take advantage of reduced nitrogen content and lower the risk of nitrogen narcosis as well as to extend bottom times.

Oxygen becomes a significant factor in diving when concentrations exceed normal atmospheric levels. 40% is considered the upper limit for recreational diving to ensure the partial pressure of oxygen remains within safe limits during dives. This is crucial because elevated oxygen levels can lead to toxicity, which can become hazardous at deeper depths, where partial pressures increase.

While mixtures with higher oxygen percentages (like 42% or even 50%) exist, those are typically used only for specialized diving applications and require advanced training and equipment to manage the associated risks. Therefore, a 40% Nitrox mix is widely accepted in recreational diving as a compromise between extending bottom times and maintaining safety regarding oxygen toxicity.