Nitrogen Narcosis

Getting 'narked' when scuba diving

Nitrogen Narcosis Martini Effect

Ever felt a little “tipsy” underwater or had an unusual sense of euphoria during a dive? Then you have probably been narked!

Nitrogen narcosis can happen when you go deep diving, generally below 30m. It is referred to as “Martini’s law” due to it being compared to having a martini every 10m in depth you descend.

This means by the time you are at 30-40m (3-4 martini’s) depth you may well feel a little drunk. Quite a few divers will go deep as they like to feel narked during a dive – considering most divers enjoy a drink and being social it shouldn’t come as a surprise.

But Why?

Narcosis is caused by the increased solubility of gases into body tissues when diving at higher pressures at depth. There is no way of telling an individual diver at what depth and how severe the narcosis will be. It can vary from person to person, and from dive to dive. Sometimes even on the same day.

Most advanced open water divers who have dived to a depth of 30m would have experienced nitrogen narcosis at some stage of their diving lives – although in and around 30 metres many wouldn’t have actually known.

Getting Narked

Narcosis isn’t dangerous in itself, it is just some of the things you can do that can pose problems. Some of the initial signs and symptoms of narcosis can be quite subtle with feelings of tranquillity, a false sense of security and mastery of the environment.

A common sign I have seen over the years is for people to giggle and laugh at things that aren’t really that funny. Similar to how you feel after a few martinis! When divers experience narcosis their thinking process slows down, their judgement will become impaired and their co ordination becomes clumsier.

You may hear a few funny stories of people trying to give fish their alternate air source or trying to put fins onto their hands and swim but I have never seen anything like that!

No Hangover!

One of the great things about narcosis is that if you feel the effects and don’t feel conformable it’s easy to cure. Simply ascend a few metres and the affects will wear off immediately – as you ascend the pressure decreases and the symptoms subside. To avoid the Narcosis completely just stay shallow.

Deep 40

For scuba divers wishing to dive to the maximum depth within recreational diving – 40metres – you need to complete some specialised training. You can do this easily within the PADI system by completing the PADI Deep Specialty. This is one of my favourite courses to teach as its lot of fun. On dive 3 the student undertakes a narcosis test at depth.

Usually when diving Koh Tao we head out to Chumphon Pinnacle for this dive as it’s easy to access 40 meters so we can see if and how narked they become. Becoming a Deep Specialty diver is a great way to access more dive sites. It’s also great to combine if you are a PADI Wreck Spec Diver as many wrecks can be deep.

PADI Deep diver training will also enhance your dive planning skills, and knowledge, reducing the risks of getting DCS. It can also contribute towards becoming a PADI Master Scuba Diver – the highest non professional rating within recreational diving.

The Test

There are many ways to test for narcosis. From mathematical equations to writing your name backwards although most of the Instructors at Crystal Dive use a hand eye co ordination task. The way the exercise is conducted is as follows….

We draw circles, squares and triangles onto a blank slate then enter numbers 1 to 10 inside the shapes. Each shape corresponds to a part of your face so circle = nose, square = forehead and triangle = chin.

Ensuring the student completes the test in numerical order, from 1-10, the student will point to the number first then point to the part of their face their face that corresponds to the shape the number is written inside.

So if number 1 is written inside a circle and number 2 is written inside a square the student would start the exercise by first pointing to their nose, then their forehead. And so on and so forth.

The exercise is first timed on land. We note down the time before repeating the test at 40 metres to compare. If there is a time difference, we can use this to gauge whether the diver was experiencing Narcosis. If there is a significant difference between the times a diver took to complete this on land, compared to at 40 metres this indicates that the diver was indeed experiencing narcosis.

Scuba Diving is all about having fun – and the Narcosis test is planned with this in mind – conducted in a controlled environment under the direct supervision of a PADI Deep Specialty Instructor. However, you should always remember safety always comes first. This is why depth limits and speciality courses have been designed specifically so divers can gain more knowledge and skills, at a pace that is suitable for their education, whilst always diving safely.

Author: Matt Bolton (PADI CD #463559)

Crystal Dive Koh Tao

7/1 Moo 2
Tambon Ko Tao
Koh Tao
Surat Thani


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