At approximately what depth does nitrogen narcosis become noticeable?

• A. Around 60 feet
• B. Around 100 feet
• C. Around 30 feet
• D. Around 150 feet

Answer: (B)

Nitrogen narcosis happens because the nitrogen you breathe becomes more narcotic as ambient pressure increases with depth. The deeper you go, the higher the partial pressure of nitrogen in your tissues, which can alter nerve function and lead to impaired judgment, slower thinking, or a sense of euphoria. For most divers, these narcotic effects become noticeable around the 100-foot (about 30-meter) mark. That depth serves as a practical benchmark in training because it’s where narcosis commonly begins to affect performance, though the exact onset varies with individual sensitivity and gas mix. If symptoms appear, ascend to a shallower depth to reduce the nitrogen load, and don’t push through impairment. Using gas with less nitrogen can lessen the risk, but does not eliminate it.