Nitrogen Narcosis: What Divers Need to Know

Nitrogen narcosis is a mysterious condition that affects scuba divers and, in rare cases, freedivers. Other names for nitrogen narcosis include: rapture of the deep, the martini effect and depth intoxication. On a dive boat, however, you’re most likely to hear: ever been narced?

What is Nitrogen Narcosis?

Put simply, it’s an anesthetic effect caused by breathing compressed gas at depth, usually nitrogen. The National Institutes of Health (NIH) have a more detailed definition.

Divers should be able to recognize the symptoms of nitrogen narcosis in themselves or a dive buddy. According to the experts at Divers Alert Network (DAN), the most common symptoms include:

Impaired judgment
Difficulty concentrating
Drowsiness
Overconfidence and euphoria
Feeling afraid

What Does Nitrogen Narcosis Feel Like?

Initially, nitrogen narcosis clouds your reasoning and judgment. That said, when you’re simply floating along with no decisions to make or tasks to complete, you may not realize you’re mentally impaired. Many divers have been narced without knowing it.

Next comes a feeling of euphoria. Divers compare the feeling to mild intoxication or getting the happy gas (nitrous oxide) at the dentist, but nitrogen narcosis affects everyone a little differently. Some divers, myself included, feel anxious and pessimistic instead of elated.

At this point, if the diver does not recognize they are narced and keeps descending, they will lose physical dexterity. Now the situation is very dangerous. Going deeper can cause hallucinations, idea fixation, stupor and much worse.

What You Can Do To Help Identify Nitrogen Narcosis

Knowing how to identify and avoid depth intoxication is an important safety skill. That’s why the PADI Deep Diver specialty course includes an activity to measure impairment at depth. At the surface, you’ll complete an activity that requires reasoning, such as a math problem or completing a simple puzzle. Personally, I liked to use one of those toys with different-shaped holes in it (a shape sorter with circles, triangles, etc.).

Underwater, your instructor will ask you to repeat the task at a depth of at least 18m/60ft, but with a slight variation. If, at the surface, your instructor asked you to subtract two large numbers, underwater the numbers will be different. For my students, I might have them put the triangle shapes in the ball at the surface, then ask them to do the circle shapes underwater.

Your instructor will record how long it takes you to complete both tasks. At depth, you may find the task is more confusing or takes longer to complete. The purpose of this activity is to help you understand how nitrogen narcosis may affect you. It’s one of several important things you’ll learn in the PADI Deep Diver course.