PADI Divemaster Certification Practice Exam

At approximately what depth do most divers commonly notice gas narcosis when using air or enriched air?

1. 20 meters/66 feet

2. 30 meters/100 feet

3. 40 meters/132 feet

4. 50 meters/164 feet

The correct answer is: 30 meters/100 feet

Gas narcosis, often referred to as "nitrogen narcosis," typically begins to be noticeable to divers at around 30 meters (100 feet) when using air or enriched air. This phenomenon occurs due to the increased partial pressure of nitrogen in the breathing gas, which affects the central nervous system and can lead to impaired judgment, euphoria, or a sense of intoxication. At shallower depths, divers may not experience these symptoms as the effects of nitrogen on the body are minimal. However, as depth increases and divers are exposed to higher pressures, the increased nitrogen absorption can lead to varying degrees of narcosis. While some individuals might start to notice it's effects even at shallower depths, 30 meters is generally recognized in diving training as the threshold where most divers begin to feel the impact of gas narcosis. It's important for divers to be aware of this condition as it can affect decision-making and overall safety during a dive. Proper training emphasizes recognizing symptoms and making plans for safe ascent if they start to feel the effects.