What must be done when encountering O2 toxicity at 20'?

In the case of encountering oxygen toxicity at a depth of 20 feet, the appropriate response is to shift to air and ventilate the divers. Oxygen toxicity occurs when divers breathe excessively high partial pressures of oxygen, leading to harmful physiological effects, which can manifest as symptoms such as visual disturbances, seizures, or other neurological issues.

Shifting to air allows for a reduction in the partial pressure of oxygen inhaled by the divers. Since the risk of oxygen toxicity increases significantly with higher oxygen levels, transitioning to air effectively mitigates the danger by restoring the breathing gas to a composition that is safer for respiration at that depth. Ventilating divers can help ensure that they are receiving adequate air during a critical moment, especially if they are showing signs of oxygen toxicity, and helps to normalize their breathing patterns.

Considering the alternatives, beginning ascent to the surface may seem like a viable solution, but it could potentially exacerbate the effects of oxygen toxicity, as rapid ascension can lead to other complications, including decompression sickness. Administering additional oxygen would increase the risk of anesthesia-like symptoms associated with oxygen toxicity, further complicating the situation. Completing decompression at 20 feet would be inappropriate in this scenario, as this would involve remaining in an environment where toxicity