Which of the following is a warning sign of oxygen toxicity?

Visual disturbances are a warning sign of oxygen toxicity because they indicate that the body is experiencing a reaction to elevated partial pressures of oxygen. Under conditions of excessive oxygen exposure, especially when diving with enriched air nitrox, the central nervous system can become overstimulated. This overstimulation can lead to symptoms such as visual disturbances, which may include blurred vision, tunnel vision, or even temporary loss of vision.

Recognizing these symptoms is crucial for divers since they can signal a need to ascend to a shallower depth to reduce the effects of high partial pressures of oxygen. Monitoring for these signs is part of responsible diving practices to ensure safety while utilizing enriched air mixes.