When do the symptoms of oxygen toxicity typically occur?

The symptoms of oxygen toxicity are most commonly associated with prolonged exposure to increased partial pressures of oxygen. When divers breathe oxygen at depths greater than what is found at the surface, the partial pressure of oxygen increases, which can lead to harmful effects on the body's tissues, including the central nervous system.

As the diver is exposed to higher levels of oxygen over a length of time, they may begin to experience symptoms such as visual disturbances, twitching, and convulsions. This phenomenon is often related to the duration of exposure rather than the immediate effects of high pressure, which means that it is important for divers using gases with higher oxygen content to monitor both their time at depth and their exposure to elevated oxygen levels.

Short exposures may not lead to immediate symptoms, and surface levels do not present a sufficient partial pressure for toxicity to occur. Additionally, symptoms do not typically manifest immediately after surfacing because the body begins to clear the excess oxygen at atmospheric pressure. Therefore, the understanding of oxygen toxicity is closely tied to how long and how deeply a diver is exposed to increased oxygen pressure.