Depth / Nitrogen Narcosis

[Amanda]

This always got me wondering...

Considering normal diving conditions

Thanks for replies...

 

[Spectre]

You need a "never been narced" category.

I know it's deeper than 91 [27 meters], but I've not been below that on air... [it's all been on nitrox].

 

[Walter]

Instead of, "never been narced" an even better category would be "who has been narced, but unaware of it?"

Seriously, we are all victims of nitrogen narcosis as we descend on either air or nitrox. We may not always be aware of feeling differently, but noone is immune. Some of learn to deal with narcosis, but our abilities are limited at depth. Everyone is subject to narcosis from approximately 60 feet (about 18 meters) and deeper. At 100 ft (about 30 meters) or deeper our abilities are seriously compromised. I rarely "feel" narced, but I've been narced many, many times. Being aware of narcosis even if you don't "feel" it can help prevent making stupid mistakes. We're all stupid when we get near 100 ft (that includes 91 ft) regardless of our EAN mixture. Heliox and trimix are a another story.

You need another category, 18 meters.

 

[WreckWriter]

You should have asked "at what depth do you FEEL narced". Everyone is measurably narced at something shallower than about 100 feet. The difference is in when we notice it. Myself, I feel it start at about 150, good and stoned at about 180. I know though, that I'm measurably impaired well shallower than that.

Since the experiences in my trimix class (it's sweet when 260 feels like 100), I doubt I'll ever dive air below 130 or so again.

Tom

 

[deepblueCkiwi]

Time to sit back and laugh at the inevitable - "I never get narced (narked?)" answers to this question!
Personally i think there are 2 kinds of narcosis - the comfortable , and the stupid.
I know i get the comfortable narcosis usually around 100ft, where you don't notice just how cold it really is....... (bad fitting wetsuits in 11c water ) which gets worse (better as u go deeper....
As for the stupid - I check my gauges and then 30secs latter i find myself thinking, hmm i looked at them, but it didn't fully register....

Ive never felt the urge to feed air to the fishies, tripping out or just plain loopy. As a recreational diver most people don't realise how impaired they really are. It's not until you have some tasks to do at depth that things really sink in. Try taking photos with a housed SLR of black coral at 200ft......You don't realise until you see the images and then wonder what went wrong!

Even better - try a chamber dive, 50m, funny voices, everything seems so funny and people can't even spell/add/think clearly.

It's all about experience, recognising when your narced is something every diver should know. My 2c's worth

 

[Amanda]

First of all, that's true, I should have added a "Never got narked" category - for the next time !

As for me, I have a question = to go from "feet" to "meters", do you divide by three ? If this is correct, then I get a bit narked at 120feet / 40meters, nevere before. When I reach 150feet / 50meters, I'm really narked. but I think that I can assume it until 180feet / 60 meters. After that, I dramatically need to be very careful - and I usually don't go deeper than that.

 

[Zept]

Originally posted by Amanda
As for me, I have a question = to go from "feet" to "meters", do you divide by three ?

10 feet is about 3 metres, so dividing by 10 and multiplying by 3 is more accurate. Or go to the Measures, Units and Conversions Web site and plug in your numbers.

120ft = 36.6m
150ft = 45.7m
180ft = 54.9m

Zept

 

[Amanda]

Thanks Zept !

And, by the way, where do you go diving in Singapore ? I've been travelling all around SE Asia for a year and a half, and always wondered where Singaporians go diving. Tioman ? Perhentian ? Sumatera ? Singapore itself ?

 

[landlocked]

Previous words by Uncle Pug.

..... just because you could not discern the narcotic effects of the nitrogen doesn't mean that you were not impaired... it just means that you lack discernment. Narcosis is not a threshold event like the sound barrier as you suppose. As the PP of nitrogen increases so does the narcotic effect and it is insidious in that it first of all robs you of awareness. Your circle of awarness diminishes and though you can (at the earliest stages) still focus clearly on what is central to your thinking you are oblivious to your surroundings. Those with discernment can regonize this at much shallower depths and can compensate to a degree for the impairment. I know guys that can pick up on what is happening as shallow as 60 fsw... not by what is seen or felt but by what is not. It takes practice.

But narcosis is just one of the hazards that diving deep on a single cylinder of air presents. It is the other hazards that will get you into real trouble... and narcosis could keep you from being aware of the situation and taking preemptive action. The chain of events that finally leads to a diving accident needs to be stopped at the earliest possible moment. Narcosis might not kill you... but it might cause you to be unaware of the little events that trigger the cascade of failures.

I believe you when you say that you are as careful at 40 feet as you are at 120 feet... the opposite unfortunately is not the case no matter what you think.

And interesting experiment which few will get the chance to try but would actually be a big help in teaching discernment:
At 80 fsw breath for a few minutes off of a helium mix and then switch back to air.
__________________
.

The point is.... at 100 feet (30 meters) you are seriously narced whether you realise it or not.

 

[MikeFerrara]

I wonder...
Are people narced at the surface?
Would my son get better grades on trimix?
Would the idiots on the road this morning have behaved more rationally on trimix?
Ever notice the deer in the headlights look on the faces of most divers at 30 feet? Maybe helium would solve more problems than we realize.