The chief factor causing nitrogen narcosis is:

The chief factor causing nitrogen narcosis is:

• A. The elevated partial pressure of nitrogen divers experience at depth.
• B. The overheating of water around the diver.
• C. The presence of oxygen toxicity at depth.
• D. The humidity at depth.

Answer: (A)

Nitrogen narcosis happens because nitrogen’s partial pressure rises with depth, and nitrogen itself has narcotic effects on the brain when that pressure becomes high. As you descend, the ambient pressure increases while you breathe a gas mix that contains a large portion of nitrogen, so more nitrogen dissolves in nerve cells and disrupts normal neural signaling. That disruption dulls thinking, slows reactions, and impairs judgment—classic narcosis symptoms. The other ideas aren’t responsible: water temperature doesn’t induce narcosis, humidity isn’t a factor, and oxygen toxicity is a separate risk tied to high oxygen partial pressure, not the narcotic effect of nitrogen.

Nitrogen narcosis happens because nitrogen’s partial pressure rises with depth, and nitrogen itself has narcotic effects on the brain when that pressure becomes high. As you descend, the ambient pressure increases while you breathe a gas mix that contains a large portion of nitrogen, so more nitrogen dissolves in nerve cells and disrupts normal neural signaling. That disruption dulls thinking, slows reactions, and impairs judgment—classic narcosis symptoms. The other ideas aren’t responsible: water temperature doesn’t induce narcosis, humidity isn’t a factor, and oxygen toxicity is a separate risk tied to high oxygen partial pressure, not the narcotic effect of nitrogen.