Scuba Diving International (SDI) Computer Nitrox Practice Exam

Which two items need to be considered when ensuring a safe Nitrox fill?

1. Gas purity and tank weight

2. Pressure and mix percentages

3. Temperature and currents

4. Local regulations and dive plans

The correct answer is: Pressure and mix percentages

When ensuring a safe Nitrox fill, it's crucial to consider pressure and mix percentages. The pressure of the fill is important because it determines how much gas can be safely compressed into your tank without exceeding the tank's designed limits. An improper pressure could lead to overfilling, which can cause safety hazards during use and handling. Mix percentages are equally vital because the specific concentration of oxygen affects both the breathing gas's properties and the potential for oxygen toxicity at varying depths. Nitrox mixtures commonly used in diving, like EAN32 or EAN36, have different oxygen levels that can impact dive planning, no-decompression limits, and safety stops. Thus, ensuring the correct mix percentage is essential for a safe dive experience. Considering gas purity and tank weight, while important for overall safety and operational efficiency, does not directly influence the immediate safety during the fill process in the same way that pressure and mix percentages do. Temperature and currents pertain more to dive conditions rather than the fill procedure. Local regulations and dive plans might factor into the overall diving operation but do not specifically ensure a safe Nitrox fill.