If a diver mistakenly uses a Nitrox cylinder, thinking it was air, he/she would risk:

Using a Nitrox cylinder instead of regular air can indeed lead to unanticipated central nervous system (CNS) oxygen toxicity, particularly if the Nitrox has a higher oxygen content than the air that the diver is used to. The air we typically breathe contains approximately 21% oxygen, while Nitrox blends often range from 32% to 40% oxygen content, or even higher in some cases.

When a diver inhales a Nitrox mixture with elevated oxygen levels at certain depths, the partial pressure of oxygen increases, which can lead to CNS toxicity. The risk of CNS oxygen toxicity heightens at depths greater than 20 meters (approximately 66 feet) for mixtures with higher oxygen content because the partial pressure becomes significant enough to potentially trigger toxic effects. These effects can include symptoms like visual disturbances, seizures, or loss of consciousness, all of which can jeopardize the diver's safety.

In contrast, shallow water blackouts and decompression sickness are related to different issues. Shallow water blackouts generally occur due to hypoxia or hyperventilation and are less directly associated with the use of Nitrox. As for decompression sickness, it is primarily related to the amount of nitrogen in a diver's body and the ascent rates, not necessarily