Diving air to 60m

[John Bantin]

Competent. Tick.
Lucky. Tick.

No man or woman is beyond chance. To think otherwise is a fool’s game.

SB is highly conservative in its views. I take risks that probably wouldn’t go down so well here.

But dying is somewhat arbitrary so just be glad despite the tigers for some reason the god chose not to take you.

Because but for the gods you would not speak. You’re one mother ******* lucky dude. Also competent. Still lucky.

My luck finally ran out when I helpfully lifted another diver's steel twinset and gave myself an inguinal hernia!

 

[InTheDrink]

My luck finally ran out when I helpfully lifted another diver's steel twinset and gave myself an inguinal hernia!

Well I hope he was ok and thumbs up for who you are and what you did. Sucks that you hurt yourself but better than a dead guy x

 

[InTheDrink]

It occurred to me that this could have been a case of IPE which is very hard to establish.
This case has 3 risk factors for IPE: female, cold and extertion

I think this is tricky. Having plent some time dying with PE diagnosis is difficult. The symptoms resemble panic and rapid ascent.

However when your lungs are full of your own water and you pass out before hitting the surface it will look like simple
drowning.

I’ll bet hundreds of divers have met their fate such so way. And considered panic divers.

When all you have is fluid in your lungs, what are your options?

 

[InTheDrink]

P.s. I think but do not know that this is more likely on CCR. NPPE is the more likely cause.

YMMD x

 

[infieldg]

TDI certified me to dive to 55m / 180ft on air (https://www.tdisdi.com/tdi/get-certified/extended-range-diver) and DAN insure me within that certification so I'll be pretty disappointed to learn that both are comfortable with me diving to within five metres of as significant a risk of death as this thread suggests cos I've done 62m and spent plenty of time in the 50's.

On the way back from a PNG dive trip yesterday I was reading a book called "The last new Guinea Salvage Pirate" by Fritz Hersheid, set in the 60's and 70's - the things they did back in the day... this is extraordinary ;

"As we got deeper George (Tyer) started to get serious and turned to face me, keeping very close, looking into my eyes, watching for any signs of narcosis. We leveled off at the 250 ft mark and George gave the OK signal. I responded positive. After a short dive along the wall we slowly returned to the surface. And that was that. After just five dives I was a certified diver".

An earlier dive required him to do an emergency free ascent from "at least 150 ft". George was pretty hard core. Yeah nah...

Fritz then convinced his girlfriend Janice to learn to dive with George and she took to it well so that George said he'd waive the fee if she agreed to try for the female world depth record on air. And buoyed by the five dives under her belt she agreed. Apparently they were all well aware of oxygen toxicity and did all their diving off navy tables and if they wanted to 'cheat', they used the less conservative French ones.

Anyhoo, after a few 250 ft dives to 'acclimatise' Janice to narcosis, plus a few at 280 ft for luck, they were ready to try for the record at 320 ft when another woman - Kathy Trout, awesome name for a diver - upped the record to 328 ft. Unphased, George simply bumped his student's goal to 340 ft (103m) at which point Janice finally said 'enough'. Apparently she thought it a teeny bit deep for a new OW student.

As much as George sounds like he wanted her dead, he himself air dived to 350 ft so he walked the walk. That's a PPO2 of over 2.3(!!!) - we're only talking 1.47 in this thread and jaws are dropping. Obviously you should be experienced and plan and prepare deep air dives, but that's exactly why we take courses like TDI Extended Range, and the deco procedures prerequisite before it, and the advanced nitrox prerequisite before that and the advanced wreck and so and so on, all of which put you through a ton of planning and executing dives (in gauge mode), assessing your behaviour at depth, testing how affected you are by narcosis with puzzles etc, asking you to perform tasks, and at least one of which requires you to have at least 30 dives deeper than 30m in your logbook first.

The part of this thread that gives ME the shivers is "single tank" and poor gear. I'm pretty sure people who get certified to do deep air dives will have appropriate gear in top condition.

 

[Storker]

On the way back from a PNG dive trip yesterday I was reading a book called "The last new Guinea Salvage Pirate" by Fritz Hersheid, set in the 60's and 70's - the things they did back in the day...

Quite. Back in the day.

Back in the day it was also common to drive a car without seatbelts - and don't even think about child seats in the back - drive a motorbike or a bicycle without a helmet or go boating without a flotation device. And people were dying from crashing without seatbelts, crashing without helmets or falling overboard without vests. And some of those who weren't unlucky and survived love to tell their anecdotes about how they did all these things and survived. Um, yeah, sure. But some of us didn't and can't tell those anecdotes because they're dead. Like some of those I hung out with back in the 70s.

These days we know better, and we have better safety equipment. And fewer people are dying in accidents. I'm also a child of the 60s and 70s, and I really prefer the safety knowledge and safety gear we have today. You won't see me in a moving car without wearing a seatbelt, and you won't see me in a boat without a flotation device. Even if I survived for many years without. Oh, yeah, and you won't see me below 3-3.5 bar pPN2, 1.4 bar pPO2 or 5.5 g/L gas density either. Even if people did those things back in the day. Because these days we know better.

 

[mafi]

Applying this argument in the context of drunken driving:

The implication is that alcohol killed. Incompetence kills. Many people should not even be in a car. Alcohol just makes it more difficult. Cars kill.

Through constant scientific advances we know that air and depth are an unsafe combination for the vast majority of the diving population. Like anything in life there are the outliers, people whom the rules physiologically do not apply. They got lucky in the gene pool. But it is unwise to adopt safety norms that are only applicable to the outliers. Its the vast majority to whom we should adopt our standards to protect then by default we protect the outliers as well.

While I agree with you on the existence of outliers, I am still yet to see a scientifically proven of diver not significantly narced at 60m. Them 'handling' and 'feeling ok' is most (99.999...%) likely just them not knowing how badly narced they really are.

 

[almostDIR]

While I agree with you on the existence of outliers, I am still yet to see a scientifically proven of diver not significantly narced at 60m. Them 'handling' and 'feeling ok' is most (99.999...%) likely just them not knowing how badly narced they really are.

If in warm water and thus being able to dive without gloves, it would be an excellent test to write a short couple of page essay about a chosen subject on wetnotes when at 60m and compare that on similar test done at 10 or 20m. preferably also record it with gopro and then compare how long it takes at different depths and how the motoric skills of using a pen etc are affected, how much hesitation between sentences, how much the handwriting itself is affected, etc.

 

[mafi]

Yes, I'd be very interested to see that. Also skills like cutting a line with a knife, long hose donate, lift bag operation, etc.

 

[Kay Dee]

While I agree with you on the existence of outliers, I am still yet to see a scientifically proven of diver not significantly narced at 60m. Them 'handling' and 'feeling ok' is most (99.999...%) likely just them not knowing how badly narced they really are.

I personally think your above assumption is too sweeping a generalisation, or your definition of significant is very different to mine. Let me try to explain my reasoning. (And of course there are a lot of variables, one size does not fit all, i.e. warm versus cold water, good versus poor visibility, quality of regulators used if OC, etc. all make a – at times big - difference with regards narcosis.)

Anyway, as we know narcosis is a mental state caused by a mind altering substance, in a divers case nitrogen at higher partial pressures. So, using an example that has been posed previously, just as a person who had never drunk alcohol, and had say three beers with a person who was a regular drinker, the inexperienced / less exposed (to alcohol prior) person would 99% of the time be more affected / impaired than the person who drank regularly.

So taking this analogy into the diving sphere, let’s say we have a diver who has never been deeper than 30m (or even 40m) on air, and has never exceeded the No Decompression Limits, or NDL’s, at those depths. Take this diver to 60m, even in clear warm water, and I agree, 99% probably would be significantly affected by narcosis, some of them possibly being even incapacitated (I have actually seen this first hand at significantly shallower depths than 60m).

Now take another diver, with the necessary equipment, that over the years (or months, depending on their frequency of diving), started out doing decompression dives (i.e. intentionally and significantly exceeding his NDL’s) using air as a bottom mix, first say in the 40m range, then after some time had passed / 'x' number of dives at that depth, ventured to say circa 50m, and again did an 'x' number of dives at that depth over time, and once capable at that depth started doing dives circa 60m. I would venture to speculate that 99% of divers that had (come that far and had) the sense to follow that sort of regime / training practice as it were, that is gradually extending their depth over time / 'x' number of dives, would not be significantly effected by narcosis at 60m and could successfully carry out tasks at that depth (and this I have also seen first hand with numerous individuals).

Also, I believe - as do some others - that ‘mind over matter’ comes into play with some people in some diving circumstances with regards narcosis. I cannot recall chapter and verse, but somewhere in the USA (Florida I believe) in late 80’s (maybe very very early 90’s?) there were some tests done that verified somewhat this statement. That is, two groups of new divers were separated and given identical tasks to do / problems to solve at depth (40m / 130ft whilst breathing air in clear warm water). The only difference was that one group was told they would be significantly affected by narcosis at 40m, the other told that there would be negligible effect (from narcosis). The results showed - although there were individuals in each group who differed from the norm – that the majority of those told they would be significantly effected were, and those told they would not be, were not, or were not affected as much as the other group was (as per the comparison of the results of the identical tests they were given to do, and post-dive how each diver reported they had subjectively felt at depth). Interestingly though, they person who scored the best, that is got the most correct answers (to the problems given) and completed / solved the tasks the quickest was a diver from the group that was told they would be significantly affected. However the overall results – in this test / series of tests(?) anyway - bore out the proposition that if you believed you would be significantly narced you would be, and if you believed you would not, then on a whole (in the test groups anyway) you were considerably less affected.

Some of the older folks here my have a better recall of where these tests were conducted than I, but Tom Mount was involved (not as a student of course) and it was conducted with a diving group attached to ??? (possibly a southern Florida university dive club, or some such organisation).

So while none of the above should be seen as an encouragement to dive air deep these days given the availability of helium in most (but still not all) places, there is no doubt that not all divers are 'significantly' affected by narcosis at 60m, and especially so dependent on conditions. And by ‘not significantly affected' I mean that they can complete the task/s (be it photography, survey, testing regulators, etc) that they set out to do, not just once but on many occasions. So IMO this cannot be put down to just luck! Also, back in the day, anyone who was significantly affected at 60m was probably soon diving on their own – or with people even less experienced than themselves - as they would likely have been weeded out / ‘excused’ long before (reaching 60m) as being a liability to the group doing dives (in that range).

I have also come across quite a few people in my travels that I only ever went to depth once with, or if I had no choice certainly separated from them ASAP on any subsequent occasion. And if they were my students, the course was either stopped, or not taken to the next level (some people accepted this and came back to continue later after they built up more experience; others just went off and ‘bought’ their certs elsewhere). Unfortunately some people are just accidents waiting to happen, be they on air, helium, or CCR. (On that note, a very good friend of mine who we did not think would survive his CCR diving ‘career’, managed to do so for quite some years, only to unfortunately kill himself later after he hung up his fins while flying his light plane. )

Be that as it may, if I had the choice would I dive a helium based mix in preference to air, YOU BET I WOULD!