Which diving scenario is most likely to lead to nitrogen narcosis?

Diving at greater depths with high nitrogen mixtures is most likely to lead to nitrogen narcosis due to the increased partial pressure of nitrogen experienced at those depths. As you descend underwater, the pressure increases, which in turn raises the amount of nitrogen dissolved in the body’s tissues. This heightened concentration of nitrogen can have a narcotic effect on the central nervous system, resulting in symptoms similar to those of intoxication, including impaired judgment and motor skills.

The risk of nitrogen narcosis becomes more significant as you go beyond recreational diving limits, typically deeper than 30 meters (100 feet). At these depths, even experienced divers may experience varying degrees of narcosis, which can affect their overall safety and ability to make sound decisions.

In contrast, shallow diving does not present a significant risk of nitrogen narcosis due to the lower pressures and dissolved nitrogen levels. High altitudes introduce different physiological challenges associated with reduced pressure but do not lead to nitrogen narcosis, as it is primarily a concern related to depth. Diving with 100 percent oxygen generally avoids the narcosis associated with nitrogen and can pose its own risks, such as oxygen toxicity, but it does not lead to nitrogen narcosis itself.