Exceeding the NDL during recreation diving

[tursiops]

Who cares what the "odds" are? If someone is spouting nonsense, then let them have it.

If not, then perhaps it makes more sense to entertain the possibility that the individual may have the intelligence, curiosity and resources to adequately research the topic without formal certification, particularly for something that is not rocket surgery, such as 10-min of deco.

Yes, that's a possibility.
But in the deco game one is always playing the odds, and you want them in your favor.

If you';d like, I'd be happy to call BS on the common SB nonsense that you can learn anything on your own and that paying somebody knowledgeable and experienced to teach you something is just a money grab on their part.

Sure, lots of quite valid and useful info can be gained without formal training. And a lot of mistakes can be made that way too; the graveyards and wheelchairs are full of good examples. The whole point is to maximize good info and minimize nonsense.

 

[Miyaru]

Yes I have learned my deco procedures on my own, from reading and from experience. Is there something wrong with that? Does everything have to be taught be a real live person in order for it to be valid?

The question is of course, rhetorical.

You are saying that divers don't do DECO as solo divers? Wow who knew.

Good divemasters won't know if a diver has done a DECO stop if the diver is not under their supervision, which would be the case if they're diving solo. You really need this spelled out?

Is the question really that rhetorical?
Yes, you can learn deco procedures on your own, by reading. Nothing wrong with that, since every course requires you to read the decompression theory.

• Is your knowledge level valid?
• Was your knowledge level validated by somebody who can correct wrong assumptions?
• If not, how do you validate your knowledge level?
• Why do you write deco in capitals? (I really need that spelled out)

Indeed, there is no diving police down there. Only Mother Nature and Murphy.
Murphy somehow manages to join you on every dive, even solo dives. Murphy is also very eager to hand out awards, especially when Mother Nature taps you on your shoulder and whispers in your ear that your number has come up.

On the other hand, dive instructors are natural selection inhibitors and they ask money for teaching you, testing you, validating your knowledge and keeping you safe. And then when you want to be certified, the agency is also asking money from you. Outrageous!


A wheelchair is more expensive than a course.
A coffin is probably also more expensive than a course.
But the good thing is that people will feel sorry for you when you end up in one of them.

 

[Angelo Farina]

Textbook example of normalization of deviance.

Or, simply, rec diving as practiceed in Europe by CMAS and BSAC certified divers. For us, planned deco IS fully rec, whilst "riding the NDL" is way more dangerous...
A dive planned with deco is generally considered SAFER than a dive planned with no deco, and which becomes deco-constrained due to errors, currents, unexpected findings, etc.

 

[Angelo Farina]

No, I did not say that. I said that Solo courses only teach NDL diving.

Well, the CMAS "equivalent" of a solo certification, called "Self Rescue Diver", explicitly describes the case of a solo diver who has deco obligations, which is a normal condition for any CMAS recreational diver.
See here the training syllabus and search for "deco" in the PDF document...
file:///var/folders/pr/zyjmmb655h7799tgdx6crty40000gn/T/MicrosoftEdgeDownloads/7bcafef3-1152-4a4a-b4cf-450ee265b663/002965-1-3.B.31.CMAS.SelfRescueDiverTrainingProgramme_New.pdf

 

[scubadada]

Not unexpectedly, this thread has become quite contentious. I have a perspective on deco diving with rec training.

So, after a 17 year hiatus, I was recertified in 1997 and have dived consistently since then in a wide variety of environments. I attained PADI MSD in 2005. I did SDI Solo in 2013. That is the extent of my formal training.

I have 2389 dives and 2385 hours of diving since 1997. I have 675 solo dives, 361 over 80 ft. I know my gas consumption quite well as I have my RMV over 1917 dives since 2010. I have only 87 light deco dives, all solo with redundant gas. My deco times have nearly all been <10 min, all less than 15 min. Personally, I don't think I am taking and inordinate risk

For several years, I padded my safety stop or deco stop. Since I bought my Teric in 2019, I have used SurfGF and have not surfaced with a GF greater than 80.

So, I have no formal training in technical diving, I think I am OK

 

[tursiops]

A dive planned with deco is generally considered SAFER than a dive planned with no deco, and which becomes deco-constrained due to errors, currents, unexpected findings, etc.

I agree completely. It is the casual entry into "light deco" on an NDL dive without preplanning for gas needs that I strongly object to.

See here the training syllabus and search for "deco" in the PDF document...

No pdf to see.

 

[lowwall]

No pdf to see.

I'm not sure if this is the current version, but it does mention gas planning including deco stops: archives.cmas.org/technique/self-rescue-diver-training-programme - Self-Rescue Diver Training Programme

 

[crofrog]

In the almost infinitesely small likelihood that both my primary and redundant gas systems failed during that maximum 5 minute stop at 10' leading to an immediate and catastrophic loss of air I would be forced to surface and risk getting bent.

So you're only planning to be able to safely handle one failure?

What would other tech divers do if diving solo and experiencing an immediate and complete loss of gas in both their main and second cylinders while still having a DECO obligation?

They've got redundant back gas and a separate decompression cylinder, and they do the planning so they can lose 2 of those and finish safely.

How many simultaneous failures can I realistically manage? What sort of failures other than the immediate and total catastrophic loss of the contents of both cylinders would I possibly be exposed to?

The fact that you don't know this shows your ignorance.

I don't get stressed to the point that I would increase my gas consumption to the point that I would use up a full 19 or 30cf pony bottle before meeting a 5 minute or less DECO obligation.

What sort of failure would delay me leaving the bottom? And any such failure would have to be reckoned with during literally ANY dive, whether the diver has 1 cylinder and no DECO obligation or two tanks with a short DECO obligation.

Entanglement, loss of visibility, navigational error, dealing with an unexpected equipment issue, unexpected workload, and task fixation are a few reasons that you could be delayed leaving the bottom.

Let's do some quick analysis; you're planning a
15 minute dive to 130ft on air using 40/85

That gives you 7 minutes of planned decompression which is inside that 5 to 10 minute range you talked about

If you're delayed in leaving the bottom for 5 minutes now your real close to or actually out of gas in your back gas

And you're looking at 17 minutes of decompression time. Which is going to outstrip the capacity of your pony pretty quickly specially if you had to use any on the bottom.

Sure you could blow 10 minutes of that off and pop out of the water at 100% gf. Doesn’t seem like a very intelligent plan in the middle of no where.


Doing that dive using GUE T1 protocols and procedures for 30 minutes at 130ft.

We’re leaving the bottom with 60cuft of back gas untouched in double 80s and 54cuft of deco gas left over if you’re diving an 80 with 50% in it.

We could be delayed around 10 minutes before we started outstripping out back gas reserves, and we’d still be no where close to the deco gas.

We could safely finish the dive without blowing off any deco with various combinations of significant delays, a complete loss of back gas for a team member, missing decompression cylinders, failed regulators etc

 

[tursiops]

I'm not sure if this is the current version, but it does mention gas planning including deco stops: archives.cmas.org/technique/self-rescue-diver-training-programme - Self-Rescue Diver Training Programme

Those are both interesting documents, but are not really about planned solo diving but rather about inadvertent buddy separation. Decompression stops are only mentioned once, in the Training documents, not the Standards document.

 

[johndiver999]

So you're only planning to be able to safely handle one failure?



They've got redundant back gas and a separate decompression cylinder, and they do the planning so they can lose 2 of those and finish safely.



The fact that you don't know this shows your ignorance.


Entanglement, loss of visibility, navigational error, dealing with an unexpected equipment issue, unexpected workload, and task fixation are a few reasons that you could be delayed leaving the bottom.

Let's do some quick analysis; you're planning a
15 minute dive to 130ft on air using 40/85
View attachment 859341
That gives you 7 minutes of planned decompression which is inside that 5 to 10 minute range you talked about

If you're delayed in leaving the bottom for 5 minutes now your real close to or actually out of gas in your back gas
View attachment 859340
And you're looking at 17 minutes of decompression time. Which is going to outstrip the capacity of your pony pretty quickly specially if you had to use any on the bottom.

Sure you could blow 10 minutes of that off and pop out of the water at 100% gf. Doesn’t seem like a very intelligent plan in the middle of no where.


Doing that dive using GUE T1 protocols and procedures for 30 minutes at 130ft.

We’re leaving the bottom with 60cuft of back gas untouched in double 80s and 54cuft of deco gas left over if you’re diving an 80 with 50% in it.

We could be delayed around 10 minutes before we started outstripping out back gas reserves, and we’d still be no where close to the deco gas.

We could safely finish the dive without blowing off any deco with various combinations of significant delays, a complete loss of back gas for a team member, missing decompression cylinders, failed regulators etc

GUE dive to 130 on air? Is that what they teach? Or are you trying to compare one diver using air and another using mixed gas and three tanks to prove????