Nitrogen narcosis is an impairment that can occur when breathing gases under increased pressure, commonly during deeper air dives. It can affect judgment, attention, coordination, and decision-making. The intensity varies between divers and dives, and a person may not recognize their own impairment reliably.
What causes nitrogen narcosis?
At depth, the increased partial pressure of nitrogen and other gases can affect the nervous system. Narcosis is associated with depth and breathing-gas conditions; it is not simply a sign of poor fitness or a problem limited to one type of diver. Other factors, including workload, stress, cold, fatigue, and individual susceptibility, may affect how a dive feels.
Possible signs and effects
Divers may notice unusual confidence or anxiety, slowed thinking, difficulty concentrating, poor coordination, confusion, or trouble carrying out familiar tasks. Symptoms can be subtle, and a diver should not rely on a single symptom checklist to decide whether it is safe to continue.
What should you do if you suspect narcosis?
Follow your training and dive plan, alert your buddy, and make a controlled ascent to a shallower depth if appropriate. Do not make a rapid ascent, hold your breath, or attempt to continue a difficult task while impaired. Reassess the dive conservatively and end it if necessary. If symptoms do not resolve or another problem is suspected, follow emergency procedures and seek medical advice.
How can divers reduce the risk?
- Stay within your training and planned depth limits.
- Avoid pushing depth limits or extending a dive because conditions seem easy.
- Plan with a buddy and agree on depth, time, gas, and turn-around criteria.
- Manage workload and avoid diving when fatigued, unwell, or impaired.
- Get appropriate training before using alternative breathing gases or planning deeper dives.
Does narcosis affect everyone the same way?
No. Individual responses and the effects of a particular dive can vary. Feeling fine on one dive does not prove that the same depth will be harmless next time. Do not use subjective confidence as a substitute for conservative planning and training.
Further reading
Review your training agency’s current deep-diving materials and guidance from Divers Alert Network. If you are unsure about depth limits or breathing-gas choices, consult a qualified instructor rather than experimenting underwater.
Recognising nitrogen narcosis while scuba diving
Nitrogen narcosis is a depth-related effect that can alter judgment, attention, coordination, or mood while breathing compressed gas. Divers may feel unusually confident, anxious, distracted, or slow to respond, and they may not recognise the change themselves. Its onset and severity vary between individuals and circumstances, so there is no single depth at which every diver will experience the same symptoms.
Reducing the risk
The most reliable approach is to stay within training and plan conservative depths, especially when conditions are challenging or a diver has limited experience. Avoid task loading, maintain buddy contact, and review the dive plan before descent. Alcohol, fatigue, illness, cold, and stress can impair decision-making and should be treated seriously when assessing fitness to dive.
What to do if symptoms appear
If you or your buddy notice impaired judgment or unusual behaviour, signal the concern and follow your training by making a controlled ascent to a shallower depth when safe. Do not continue deeper or rely on willpower to overcome symptoms. If symptoms persist after surfacing or there are other concerning signs, seek professional medical advice. Training, conservative planning, and a calm response are more useful than trying to predict exactly when narcosis will occur.