Nitrogen Narcosis

Divers fondly call it 'narked' while others call it more poetically as 'ruptures of the deep'. It is a condition whereby the diver behaves as if intoxicated by alcohol while breathing on compressed air. Symptoms are typically apparent near depths of about 100ft.


There are a number of theories why this condition occurs but none can produce an adequate explanation for all the observed symptoms of nitrogen narcosis. It is however agreed that breathing compressed air in depths of around 100ft, where the partial pressure of nitrogen increases is linked to the condition. This increase in pressure causes more nitrogen to be dissolved in the tissues, especially in fatty tissues (lipids). Nitrogen narcosis has similar effects as those of anesthetic agents and sedatives such as nitrous oxide (laughing gas)  and alcohol. Nerve cells contain a lot of fat tissue and these are important to conducting electrical impulses. The build up of nitrogen in these fats impede the impulses of nerve cells. Nerve cells in the reticular formation of the brain, which controls the state of alertness and consciousness of the diver, are particularly sensitive to nitrogen and other narcotic agents. All sensory pathways feed into this system, which monitors the information coming into the brain and identifies important stimuli. Hence when it is depressed by the anesthetic effects of nitrogen, neural pathways are disrupted and the diver experiences narcosis.


Different individuals have different susceptibility to nitrogen narcosis. Factors such as the diver's personal fitness, state of mind, health and age contribute the how easily the diver gets the condition. Environmental factors like cold and poor visibility can also increase the susceptibility.

At shallow depths, symptoms are mild impairment of concentration and ability to reason, slight delay in response to stimuli and mild euphoria. As the diver goes deeper, this symptoms worsens. The diver will start making more serious mistakes in judgment while becoming more overconfident. This is serious as the diver would be similar to a drunkard refusing to admit he's drunk. Because the diver is in a state of 'drunkenness', chances of the diver unwittingly getting DCS also increases.  Soon confusion and hallucinations sets in and finally leading the diver to drown.

The chart below shows how the symptoms worsens as the diver goes deeper.


Narcosis, unlike being drunk or on drugs, improve almost immediately upon ascending to shallower depths. However care must be taken when assisting narked divers as they can be violent such as a drunkard might behave. To prevent the onset of narcosis, the diver can make sure he has enough rest, allow enough time for the effects of drugs and alcohol to clear prior to the dive, and maintain his level of fitness.

DCS Nitrogen Narcosis Gas toxicity





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