SDI Open Water Scuba Diver Practice Exam

What is the chief cause of nitrogen narcosis?

1. Rapid ascent from depth

2. The elevated partial pressure of nitrogen experienced at depth

3. Cold temperatures underwater

4. Dehydration before diving

The correct answer is: The elevated partial pressure of nitrogen experienced at depth

Nitrogen narcosis occurs primarily due to the elevated partial pressure of nitrogen that divers experience when descending to significant depths. As a diver goes deeper, the pressure of the surrounding water increases, which also increases the partial pressure of gases, including nitrogen, in the breathing mix. This heightened partial pressure impacts how nitrogen affects the brain and body, leading to symptoms such as euphoria, impaired judgment, and decreased motor skills, akin to alcohol intoxication. While rapid ascent, cold temperatures, and dehydration can all introduce risks or complications during a dive, they are not the primary reasons for nitrogen narcosis. Rapid ascent can lead to decompression sickness, but it does not cause the narcotic effects associated with nitrogen. Cold temperatures can affect physiological responses and comfort but do not directly cause nitrogen narcosis. Dehydration may lead to fatigue and other issues, but it does not influence the onset of narcosis related to nitrogen saturation in the body.