Decompression and the recreational diver

[Rhone Man]

In the Advanced Scuba Discussion forum today, the top three subjects are:

• The definition of Recreational Diving vs. Technical.
  
• Does defining "technical diving" serve any purpose?
  
• Do You Consider Solo Diving to be Recreational or Technical?

Whilst everyone is thinking about these subjects, I want to throw another one out.

If one accepts that it may be acceptable for "non-technical" divers to engage in solo diving, provided they have (amongst other things) the proper training on gas planning and redundant gas supplies, should there be any objection to training recreational divers to conduct "light deco" dives. By "light deco", I mean envisaging using your back gas only for decompression, and limiting the mandatory decompression stop to, say.... 6 minutes.

Let's be clear - lots of experienced divers do this in practice anyhow. So what we are really discussing is whether if agencies (first SDI, now seemingly PADI) start to accept solo diving as appropriate for properly trained and equipped recreational divers, why not "light deco" to?

It does very much blur what the core boundary line which usually used to distinguish "technical" diving (see Andy's article). But (speaking from my personal diving practices) for me there is a world of difference between carrying a rich deco gas (or two) on a dive where I am planning either an extended stop or series of stops to off-gas, and simply running a "long" recreational dive acknowledging that I am going to have to sit at 15 feet for a while longer breathing back gas at the end of the dive before I can surface.

 

[GrimSleeper]

Yes, experienced divers often start pushing their profiles and carrying out 'light' deco. But what constitutes 'experienced'? You, Rhone Man, with over a thousand dives and some technical training, are an experienced diver. If you want to do a little back-gas deco, you understand the risks, you probably have an understanding of what to do if it all goes wrong, where's the problem? (Other than the fact that, arguably, you can't decompress air with air properly and at some point you'll still get bent no matter what your computer says... But that's a whole other discussion).

Get an agency involved, and what will constitute 'experienced'? One hundred dives? Fifty? Twenty? Five? Given the number of people I encounter who think that fifteen lifetime dives makes them 'pretty experienced, you know,' and that I'm being unreasonable refusing to take them into a 33m deep, dark, silty overhead environment, you're just going to end up with a whole bunch of divers trying to take short cuts to places they are not ready to be. Many divers can't even be bothered to retain the basic information presented to them in Open Water. How is teaching 'light deco' as a discipline going to improve anything?

There already are agencies that include much of what everyone's talking about in their curricula, such as BSAC and CMAS. And they mostly turn out pretty decent divers, but I've still had a CMAS three-star diver earnestly explain to me that his computer always started giving him more no-deco time as his air got lower (it was showing time-to-surface, and he had no idea that he was repeatedly blowing off required deco until I explained it to him). Not to mention the BSAC instructor who was mystified that his air-only computer locked out after doing a nitrox dive on which he just tagged along with everyone else. Even a lot of dives doesn't always equate to meaningful 'experience'.

If people want to do unplanned deco, which is - let's be honest - what we're talking about in most cases... There's no scuba police out there stopping them. But what's the motivation in shouting about it, or pushing for it to be a recognised diving discipline?

 

[Mike Boswell]

You can't do the decompression stop without the gas,
And you won't have the gas unless you planned for it,
And you can't plan for it without the knowledge,
And you won't have the knowledge without the training,
And you won't get the training in a recreational course.

 

[DevonDiver]

To me - the issue revolves around the necessity to maintain the deco stop. It's a virtual ceiling, but nonetheless it is very real.

Technical diving isn't just about the use of exotic gasses - it's about having a very high standard of core skills, extensive planning/preparation and covering all reasonable contingencies so that the deco obligation can be achieved. Nothing in the recreational diving syllabus comes close to providing that level of training, that focus or that mindset.

Any argument that divers can take a 'recreational' approach to decompression diving has to be based on a limited scope of decompression. It has to be 'light' decompression. What I see in those arguments is a mindset to deco that links 'light' with 'safe if broken'. "It's only 6 minutes, so if I screw up, then I'll be ok". In essence, it is reducing 'light deco' to the status of a glorified safety stop. It's a dangerous and irresponsible mindset to encourage/allow.

How many 6 minute light deco/glorified safety stops does the diver have to complete, before they feel confident and justified to extend to 10 minute stops? to 15 minutes? to 20 minutes?

How many times do they accidentally or deliberately break their virtual overhead, before they start to believe that "deco is all hype" and begin rationalising that the implications for skipped 'light' deco obligation are inconsequential? How long will it be before they start scoffing at "You're gonna die" comments when they gain the confidence to start admitting that they've blown their 'light' deco through lack of preparation, planning and/or dive ability.

There really is no need to justify decompression without training. Training is now commonly available and easily accessible to the dive community. It's no longer a mysterious 'dark-side'.

This weekend I am teaching a PADI Tec40 course. My student has 50 dives experience, certified as an AOW & nitrox diver. The cost of his course is the same as I charge for an Open Water course. It'll take 4 days. The first day is 'recreational' deep open-water dives - 'check-outs' where I can assess and remediate his core skills. Then we have 3 days of 'tech'. The theory work is intense - detailed dive planning techniques, equipment configurations and 'technical mindset'. We also have 4 training dives. The first 3 dives are shallow-water and skills intensive. He'll learn to safely operate doubles and a single stage of nitrox (-/=50%). He will learn how to gas switch and hold a deco stop with precision. The course will finish with a single, planned decompression dive to a maximum depth of 40m/130ft with no more than 10 minutes of deco.

On qualification, he'll be certified to conduct decompression dives, to a maximum of 10 minutes deco, down to 40m/130ft, using nitrox up to 50%.

Isn't that the sort of 'light' deco we are talking about?

Does that course sound unreasonable in terms of scope, time, cost or commitment?
Does the course sound excessive for the benefits gained?
Is there any mystique or 'black magic' involved?

 

[waterpirate]

My problem with the tech 40 as you describe is that it is light deco with training wheels. Max ten minutes deco? Most tech instructors I run into have very high standards for accepting anyone into a adv ntx/deco proc class. Either you are ready for 30 at 30 with 30 accumulated or you are not.

I think that easing into the pool with light deco, no matter what we are calling it is a crutch. I would draw the line at an intro to tech class and then either go straight to you accept the risks involved with 30/30/30 or not. While education at an early stage is good, I do not agree with teaching so light a deco. The argument could be made that cause there is nothing to 30/130/10 then deco to deeper depths for longer is just as easy.

At the end of the day I think we are overloading on this crap talking about it. People do what people do. Some do it foolishly and some seek out training and some figure it out on there own with the help of mentors. Clearly there can be no hard and fast rules for which diver you will be. Personally I think if you have to defend your position..... You are prolly teetering on the edge.

As has been talked to death the differance between tec and rec in my opinion need not even exist, they are just labels. Being trained to dive to the depths that you hope to conduct dives safely is priceless. When is someone ready for more?

In the begginning you gas out prior to timing out.
Later that begins to change
Now you need more
And so on
Eric

 

[DivemasterDennis]

However, the training can come is a formal class or from divers competent and experienced in doing the type of dive contemplated. That is what I did on the few deco dives I have done. I learned alot, but not enough to plan and do one on my own. I would want to get more practical experience with those who make such dives regularly. Mike Boswell's point is well taken.
DivemasterDennis

 

[Mossman]

The first "light deco" diving I did was in Truk. Bottom time was limited on the deeper dives and we were doing 4-5 a day. One one 5th dive early in the trip, I spent the dive chasing my computer's NDC limit as I ascended, trying to stay down as long as I could. When I bitched about it back on board, someone more experienced advised me not to worry so much about getting into a little deco. I soon learned that if I overstayed my NDLs by a few minutes, it would result in only a few minutes of deco. With an over-filled 112 on my back and a buddy with the same, NDLs were limiting us even on nitrox - we had plenty of air left on most dives, and the Odyssey hung a tank off the deco bar for good measure. At this point, however, I had over 100 dives under my belt in varying conditions and was in the midst of DM training.

Now I dive with a Suunto D9 which is very conservative. There have been times when diving with J and her Uwatec when I've been forced to do "light deco" to satisfy Suunto's model, while J was free to surface (though she generously stayed with me). While I've since had basic tech training, it's mainly my experience with standard recreational profiles, my own air consumption, and the 300+ dives I've done with the Suunto that "tell" me when light deco is OK and how much I'll be able to complete. Having a buddy with a more liberal computer and additional air adds a safety factor. I would not do "light deco" dives solo without at least some redundancy.

I wonder how European recreational training, which often includes light deco from what I hear, varies from U.S. recreational mandates against incurring any mandatory deco.

 

[fdog]

You can't do the decompression stop without the gas,
And you won't have the gas unless you planned for it,
And you can't plan for it without the knowledge,
And you won't have the knowledge without the training,
And you won't get the training in a recreational course.

Succinct and to the point. Well said.


All the best, James

 

[Akimbo]

… If one accepts that it may be acceptable for "non-technical" divers to engage in solo diving, provided they have (amongst other things) the proper training on gas planning and redundant gas supplies, should there be any objection to training recreational divers to conduct "light deco" dives. By "light deco", I mean envisaging using your back gas only for decompression, and limiting the mandatory decompression stop to, say.... 6 minutes…

You can be certified as a solo diver and not as a technical diver. Technical divers are not certified as solo divers. Neither is a prerequisite for the other. No certification is “required” to do either.

… Let's be clear - lots of experienced divers do this in practice anyhow. So what we are really discussing is whether if agencies (first SDI, now seemingly PADI) start to accept solo diving as appropriate for properly trained and equipped recreational divers, why not "light deco" to? ...

In the end, all of our ruminations on what is “acceptable” are pointless:

• Anyone can buy diving gear from a dive shop, the Internet, or used — including rebreathers, commercial diving helmets, doubles, drysuits, and Trimix computers.
• Very little if any knowledge is required to get cylinders filled since very few shops actually ask to see a C-card. Even when they do, all it takes is a paint ball label.
• There are dive boats that only require a signed release that states you are certified to perform the intended dives with no additional proof. Besides, any idiot can buy a boat easier than buying a car.
• All the technical information required to successfully make extensive decompression dives has been widely available longer than the vast majority of us have been alive.
• Shopping for a computer leads you to believe that it will tell you everything you need to know about decompression, at least until you get to the fine print in the manual which nobody reads anyway.

Based on my observations, the current level of open water training is so marginal that a good swimmer motivated to teach themselves to dive through self-study could, if not likely, become safer diver than an the average open-water recently certified diver who isn’t interested in learning or can’t afford more merit badges. The same is true for divers in poor physical condition that have a pocket full of C-cards including Trimix, rebreathers, and instructor.

What does it really matter what certifying agencies say? The premise of this conversation is lots of people ignore their recommendations anyway. Those that don’t do so by personal choice. The reality is that the individual is the only person that can determine what is acceptable to them. We can wring our hands all day and nothing will change. Unfortunate but ultimately true, Darwin is the final arbitrator.

 

[Jaydubya]

There are agencies right here in the US that teach light deco as part of their recreational curriculum. Example: IANTD Advanced Recreational Trimix. I don't have the book in front of me but the limitations are something like 160 fsw, one gas switch, and 15 minutes of mandatory decompression on an oxygen rich mixture. This course is considered a recreational course and is one of the prerequisites for moving on to technical diver or normoxic trimix diver training.