Scuba Diving International (SDI) Computer Nitrox Practice Exam

What changes must be made to a regulator for use with Nitrox mixtures of 40 percent FO2?

1. Significant modifications

2. No changes needed

3. Replace all seals

4. Requires special cleaning

The correct answer is: No changes needed

Using a regulator with Nitrox mixtures of up to 40 percent oxygen does not necessitate significant modifications. Regulators designed for air are generally safe for mixtures containing up to 40 percent oxygen, which is the upper limit for recreational diving Nitrox blends. At this concentration of oxygen, the materials commonly used in standard regulators are compatible, as they can handle the increased partial pressure of oxygen without risking a fire or failure. This is because 40 percent oxygen is still within a range that does not pose the same risks of oxygen toxicity or combustion as higher concentrations would. However, beyond 40 percent FO2, or in situations involving higher pressures and specific compositions, different procedures and cleaning standards might come into play to ensure safety and compatibility with pure oxygen. These measures typically involve replacing seals and special cleaning to remove any contaminant that could pose a risk when using higher percentages of oxygen. However, for the context of using a Nitrox mixture with 40 percent FO2, such precautions are not required. Understanding these nuances is crucial for ensuring safe diving practices while using Nitrox mixtures, but for standard mixtures used by recreational divers, the existing equipment usually suffices without significant modifications.