Scuba Diving International (SDI) Computer Nitrox Practice Exam

Which of the following statements about oxygen toxicity is true?

1. It is not a concern at greater depths

2. It can occur with different Nitrox mixtures

3. It only occurs when using pure oxygen

4. It is prevented by increasing dive duration

The correct answer is: It can occur with different Nitrox mixtures

Oxygen toxicity is a significant concern in scuba diving, particularly when using nitrogen-oxygen mixtures such as Nitrox. The correct statement highlights that oxygen toxicity can occur with different Nitrox mixtures, emphasizing that various concentrations of oxygen can lead to toxicity under specific conditions, particularly at greater depths. When divers use different Nitrox blends, the percentage of oxygen in the mix can approach levels that pose a risk for toxicity, especially if a diver exceeds certain partial pressures of oxygen. The risk is more pronounced at deeper depths due to the increased pressure of the surrounding water, which increases the partial pressure of oxygen in the breathing gas. Therefore, it is crucial for divers to understand the risks associated with the oxygen content in their chosen gas mix and adhere to guidelines regarding maximum operating depths (MOD) for those mixtures. On the other hand, the other statements misrepresent potential scenarios regarding oxygen toxicity. It is indeed a concern at greater depths due to increased ambient pressure effects. Also, oxygen toxicity can occur with any Nitrox mixture that contains elevated levels of oxygen, not just pure oxygen. Lastly, extending dive duration does not prevent oxygen toxicity; rather, it can increase the risk if the diver remains at depths where the partial pressure of oxygen is high. Understanding these aspects is