What is commonly one of the first actions if a diver suspects oxygen toxicity?

If a diver suspects oxygen toxicity, one of the first actions taken is to ascend to a shallower depth. This is crucial because higher partial pressures of oxygen can exacerbate the symptoms of oxygen toxicity, which can include visual disturbances, ear ringing, twitching, or convulsions. By ascending to a shallower depth, the partial pressure of oxygen decreases, effectively reducing the risk of further toxicity symptoms manifesting and allowing the diver to manage the situation more safely.

While other options may seem viable under certain circumstances, continuing the dive can increase the risk, switching tanks may not address the underlying issue of depth and partial pressure, and changing dive patterns does not immediately alleviate the potential effects of oxygen toxicity. Ascending is the most direct and effective response to mitigate the immediate threat posed by excessive oxygen exposure.