Scuba Diving International (SDI) Computer Nitrox Practice Exam

Why might oxygen partial pressure become critical during a Nitrox dive?

1. To prevent hypoxia

2. To enhance buoyancy

3. To ensure safe ascent

4. To avoid oxygen toxicity

The correct answer is: To avoid oxygen toxicity

During a Nitrox dive, managing the partial pressure of oxygen is crucial to prevent oxygen toxicity. This condition occurs when the partial pressure of oxygen exceeds safe levels, which can lead to neurological and pulmonary problems. Each gas contributes to the total pressure in the environment; thus, as a diver descends, the partial pressure of oxygen in the breathing mix increases. If the level becomes too high—typically above 1.4 ATA for most divers—it can pose significant health risks, including convulsions and other severe symptoms. Understanding the safe limits of oxygen partial pressure allows divers to plan their dives effectively, ensuring they remain within a safe range to avoid the risks associated with elevated oxygen levels. This emphasizes the importance of careful nitrox mix selection and dive planning to maintain safety during the dive. The other options, while relevant to general diving safety, do not address the critical concern of managing partial pressure of oxygen specifically.