Scuba Diving International (SDI) Computer Nitrox Practice Exam

What is a commonly known downside of using higher percentages of oxygen in a diving mix?

1. Increased risk of decompression sickness

2. Increased likelihood of oxygen toxicity

3. Reduced buoyancy

4. Higher surface interval requirements

The correct answer is: Increased likelihood of oxygen toxicity

Using higher percentages of oxygen in a diving mix significantly increases the likelihood of oxygen toxicity, which is a serious concern for divers. When divers utilize nitrox blends with elevated oxygen levels, the partial pressure of oxygen rises, especially during deeper dives. This can lead to symptoms of oxygen toxicity, which may manifest as visual disturbances, nausea, seizures, or even unconsciousness in severe cases. Oxygen toxicity can be categorized into two types: central nervous system toxicity and pulmonary toxicity. Central nervous system toxicity is particularly relevant to divers, as it can occur during exposure to high pressure conditions for extended periods. Divers must carefully monitor their depth and the oxygen levels in their mix to avoid exceeding the safe limits set for oxygen partial pressures. Understanding the concept of partial pressure is essential in this context. The deeper a diver goes, the higher the pressure, and thus the greater the effective oxygen percentage experienced by the body. Therefore, training and adherence to guidelines are crucial to safely managing the risks associated with higher oxygen levels in diving mixes. This focus on oxygen toxicity explains why it is a well-known downside of using nitrox with elevated oxygen content in diving.