Scuba Diving International (SDI) Computer Nitrox Practice Exam

What is the most important setting that must be made to your Nitrox computer before every dive?

1. Depth limit setting

2. Oxygen % (FO2) must be set

3. Temperature setting

4. Altitude adjustment

The correct answer is: Oxygen % (FO2) must be set

Setting the oxygen percentage (FO2) on your Nitrox computer is crucial before every dive because the composition of the breathing gas directly affects your limits for safe diving. Each Nitrox mixture has a specific percentage of oxygen, and this affects both your no-decompression limits and the maximum operating depth. If this setting is not accurate, you could inadvertently exceed your planned limits for that specific gas mixture, potentially leading to oxygen toxicity or decompression sickness. Properly adjusting the FO2 ensures that your dive computer can calculate the necessary information, such as no-decompression limits and ascent rates, based on the actual gas you will be breathing under water. This setting is vital for maintaining safety during dives using enriched air Nitrox. In contrast, depth limit settings, temperature adjustments, and altitude changes are important but secondary compared to the accurate setting of the oxygen percentage, as they do not directly account for the specific physiological impacts of the gas you are using.