Which of the following is NOT a CNS Oxygen Toxicity prevention measure?

• A. Ensure equipment is in good order.
• B. Observe depth-time limits.
• C. Avoid excessive exertion.
• D. Increase oxygen exposure by staying at depth.

Answer: (D)

The main idea is preventing CNS oxygen toxicity by controlling how much oxygen you breathe under pressure. CNS toxicity happens when the partial pressure of oxygen in the breathing mix becomes too high, especially underwater. To prevent it, you keep oxygen exposure within safe limits through careful planning of depth and time (following depth-time limits), make sure equipment is functioning properly so you don’t have accidental hyperoxia, and avoid excessive exertion which can raise oxygen demand and risk. Increasing oxygen exposure by staying at depth, however, raises the ambient pressure and the partial pressure of oxygen, which heightens the risk rather than preventing it.