When is oxygen toxicity present in an atmosphere?

Oxygen toxicity occurs when the concentration of oxygen in the atmosphere exceeds a certain threshold, leading to harmful physiological effects. Normally, the ambient air contains about 21% oxygen. When oxygen levels rise above 23.5%, it begins to have toxic effects due to increased partial pressures that can lead to hyperoxia.

At levels higher than this, the risk of central nervous system toxicity increases significantly, potentially causing symptoms such as visual disturbances, twitching, and seizures. This is particularly important in contexts such as deep-sea diving or in hyperbaric oxygen therapy, where individuals are exposed to higher-than-normal levels of oxygen. Thus, the correct identification of this threshold level is crucial for safety in environments where oxygen concentrations can become elevated.