When it is breathed under pressure, nitrogen has an intoxicating effect. The effect will be experienced by all divers breathing air at depth in excess of 30 meters (100ft), although some divers may notice the effect at shallower depths. It increases with depth, but it is quickly reversed on ascent but if the symptoms persist after the ascent to the surface, the cause is something other than narcosis.

Factors that increase a diver's likelihood of suffering Nitrogen Narcosis:
• Anxiety, apprehension or inexperience
• Recent intake of alcohol or certain medications/sedative drugs
• Fatigue or heavy work
• Excessive carbon dioxide
• Cold water or poor visibility

Signs & Symptoms of Nitrogen Narcosis:
• Impairment of reasoning, judgement, memory, concentration and attention
• Sense of well-being, light-headedness
• Anxiety, loss of coordination, judgement or skill
• Hallucinations, unconsciousness, death (at extreme depths)

First Aid Treatment for Nitrogen Narcosis:
• Protect the diver from injury until the ascent is sufficient to eliminate the narcosis