Nitrogen Narcosis — What It Is and Why It Matters
Nitrogen narcosis is a reversible alteration in consciousness caused by breathing nitrogen at elevated partial pressures during deep dives. Often called "rapture of the deep" or "getting narced," its effects resemble alcohol intoxication: impaired judgment, slowed reaction time, euphoria, tunnel vision, and difficulty with complex tasks.
Narcosis becomes noticeable for most divers between 30 and 40 meters (100 to 130 feet) and worsens with increasing depth. The effect reverses immediately upon ascending to shallower depth. Technical divers mitigate narcosis by using trimix — a breathing gas that replaces some nitrogen with helium, which is far less narcotic.
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Frequently Asked Questions
At what depth does nitrogen narcosis start?
Effects vary by individual and conditions, but most divers begin to notice narcosis between 30 and 40 meters (100 to 130 feet) on air. Cold water, poor visibility, stress, and fatigue can amplify the effect at shallower depths.
Is nitrogen narcosis dangerous?
It can be. While the sensation itself reverses on ascent, impaired judgment at depth can lead to dangerous decisions — like descending deeper, ignoring instruments, or failing to notice a problem. This is a primary reason recreational dive limits are set at 40 meters.
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