Scuba Diving International (SDI) Computer Nitrox Practice Exam

What is the maximum percentage of oxygen that sport divers use in a Nitrox mixture?

1. 36%

2. 38%

3. 40%

4. 42%

The correct answer is: 40%

The maximum percentage of oxygen that sport divers use in a Nitrox mixture typically does not exceed 40%. This percentage is important because as the oxygen percentage increases beyond this threshold, the risk of oxygen toxicity also increases significantly. For recreational diving, Nitrox mixtures are commonly used with oxygen levels ranging from 32% to 40%, allowing divers to extend their bottom time and reduce nitrogen absorption compared to air. It is widely accepted that using a Nitrox blend with 40% oxygen represents an optimal balance for most sport divers. While mixtures above this level exist, they are generally reserved for more advanced or technical diving practices where divers have received specialized training to manage the increased risks associated with higher oxygen concentrations. Understanding this saturation point is essential not only for safety but also for planning dives effectively, including calculating no-decompression limits and ensuring adequate surface intervals. Thus, the choice of 40% is aligned with safe diving practices and the knowledge base established within the diving community.