Equivalent Air Depth question

[Akimbo]

I’ve done that to 70 metres but everyone has a limit and it doesn’t last. After a break of a few weeks your back to square one.

That is completely consistent with the experience I was attempting to describe.

Problem with narcosis is you’re largely unaware of the affects until it’s serious.

That is inconsistent with my experience and observations of people I have worked with. That said, this group tends to be self-limiting. Divers who are uncomfortable on deep air don't accept deep air jobs and those that perform poorly don't get called for those jobs. To a considerable degree, the same sort of thing happens with recreational divers.

 

[Celt]

Problem with narcosis is you’re largely unaware of the affects until it’s serious. A lot like watching a youth drinking alcohol, they’re unaware of their behaviour as others around them see it very differently.

You’re totally aware of it, but you single minded do the job. When you land on a mound of pre nuclear brass bars narcosis is the last thing you’re bothered about. How to get as many in the boat as quickly as possible was all we thought about.

 

[Bob DBF]

Yep, rules never seem to retire. Remember being told that you can't go in the water within an hour of eating?

Does Plucking a Gray Hair Make More Grow? And More Old Wives Tales That Are Fake

These long-believed "facts" don't exactly hold any truth.

www.goodhousekeeping.com

It only worked for my parents when they were around at the time.

 

[ginti]

Divers who are uncomfortable on deep air don't accept deep air jobs and those that perform poorly don't get called for those jobs. To a considerable degree, the same sort of thing happens with recreational divers.

Except that divers who perform poorly can go diving, and usually do that because no one has the interest to stop them...

 

[Wibble]

You’re only aware of narcosis when it’s significant enough to notice.

Do a chamber dive to 40m/130ft and you’ll be giggling like schoolgirls. Do any basic task and you’ll be far more impaired than you realise. Three or four pints impaired.

When you’re pissed you notice these changes in personality (loud, gregarious, uninhibited, etc. — which is why we drink!). You notice the physiological changes (leaning on the bar, balance, coordination, etc.) and the psychological changes (distraction, lack of focus, need to dad dance, etc.)

Something is odd about being wet. It’s like your senses are numbed, mainly because you’re not using balance, here’s little to hear, limited sight, wearing thick exposure protection (attenuating touch sensitivity), not communicating nor socially interacting (thus not using higher functions which give feedback as to your impaired behaviour). But you are impaired, especially for higher level skills of logical reasoning, deduction, memory, etc.

As you dive much deeper on air results in you becoming more and more impaired, eventually being unable to perform basic reasoning. Even becoming unaware of serious life threatening situations — almost paralysed (have read many accounts of divers rescuing other divers and once shallower they wake up.

Helium is your friend.

 

[Celt]

You’re only aware of narcosis when it’s significant enough to notice.

Do a chamber dive to 40m/130ft and you’ll be giggling like schoolgirls. Do any basic task and you’ll be far more impaired than you realise. Three or four pints impaired.

When you’re pissed you notice these changes in personality (loud, gregarious, uninhibited, etc. — which is why we drink!). You notice the physiological changes (leaning on the bar, balance, coordination, etc.) and the psychological changes (distraction, lack of focus, need to dad dance, etc.)

Something is odd about being wet. It’s like your senses are numbed, mainly because you’re not using balance, here’s little to hear, limited sight, wearing thick exposure protection (attenuating touch sensitivity), not communicating nor socially interacting (thus not using higher functions which give feedback as to your impaired behaviour). But you are impaired, especially for higher level skills of logical reasoning, deduction, memory, etc.

As you dive much deeper on air results in you becoming more and more impaired, eventually being unable to perform basic reasoning. Even becoming unaware of serious life threatening situations — almost paralysed (have read many accounts of divers rescuing other divers and once shallower they wake up.

Helium is your friend.

I’m exactly the opposite, the minute I get in the water I’m hyper aware. I’m watching for every little oddity or anything not quite right. Especially solo or in poor conditions. It’s like a sixth sense kicking in. My sense of touch is heightened and my night vision kicks in. My movements become slow and deliberate.

 

[Wibble]

I’m exactly the opposite, the minute I get in the water I’m hyper aware. I’m watching for every little oddity or anything not quite right. Especially solo or in poor conditions. It’s like a sixth sense kicking in. My sense of touch is heightened and my night vision kicks in. My movements become slow and deliberate.

Do you think that's experience? Has that changed over the years?

 

[Celt]

Do you think that's experience? Has that changed over the years?

Experience plays a part wibble but any diver can practice self awareness, I think it’s about not letting your mind wander into silliness. Especially when you’re diving, this may seem odd but I have a little ritual that I do every dive before going under. I take of my mask and breath underwater with my face exposed until my breathing completely relaxes. It’s like moving from land to water, I then clear my mask and drop down into diving mode. Underwater and on land are totally different environments and you must change your attitude when you move from one to the other.

 

[Akimbo]

Do a chamber dive to 40m/130ft and you’ll be giggling like schoolgirls.

The giggling starts on chamber runs at about 20M/60' when first timers notice their voice change. It is a cool new experience and most people are pumped.

I never heard of a diver being booted from US Navy second or first class diving school for low NN tolerance. When I went through school, Second Class divers were certified to 150'/46M and First Class was 285'/87M on air. Dives were first done in a dry chamber, which is easier to learn in than in the water. They were followed up by wet dives, in the ocean for Second Class and a wet chamber for First Class, since the school was in Washington DC.

You can absolutely learn to manage narcosis, which was the point of these dives. It was not to eliminate candidates. Cousteau's description of NN in his book, The Silent World, has done more to mislead new divers than anything ever written. No, you do not try to buddy breathe or share air with fish.

 

[Kay Dee]

...................You can absolutely learn to manage narcosis..........

Absolutely agree 1000%, the key words being "learn to manage".

That is not to say I recommend deep air diving. Certainly I preferred to dive, and would recommend, a helium mix, as there can be some circumstances where the narcosis factor could become the difference between life and death, especially if diving in 'adverse conditions' as some folks, even very experienced folks, unfortunately found out the very hard way.

After all, as Dirty Harry said, "A mans gotta know his limitations".