Diving with gradient factors for a new recreational diver

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inquisit

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@Angelo Farina do you have any distinction between the "hardly any plan required to stay safe" dives and otherwise? Since you don't use the word "technical" to differentiate, is there some description or division that is commonly drawn on your side of the pond?
 

ginti

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@Angelo Farina do you have any distinction between the "hardly any plan required to stay safe" dives and otherwise? Since you don't use the word "technical" to differentiate, is there some description or division that is commonly drawn on your side of the pond?
the distinction for European agencies is usually 50m:

But it changes country by country; in France, I **believe** it is the use of helium (deep air, up to 70m and sometimes even slightly more, is still relatively common)
 

Angelo Farina

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@Angelo Farina do you have any distinction between the "hardly any plan required to stay safe" dives and otherwise? Since you don't use the word "technical" to differentiate, is there some description or division that is commonly drawn on your side of the pond?
We have techincal diving here, and the boundary between recreational and technical is sharp. As said, here we do not have many "shops", instead we have many "diving centers". They are clearly differentiated between recreational and technical.
In the first ones you only get air and nitrox, the max depth is set to the rec limit (usually 50m), and divers are required to show normal rec certifications.
In technical diving centers (or diving clubs) they use advanced gas mixtures, both for bottom and for deco (they use accelerated deco, which is not used by rec divers), rebreathers, and there are no depth limits.
The only significant difference between US agencies and European no-profit organizations is in the concept that, diving at depths greater than 30m, a planned deco is the way to go, instead of attempting to narrowly avoiding deco obligation.
It is more a cultural factor: when things are going close to be problematic, we prefer to consider them already fully problematic, and treat it consequently.
You see this cultural difference in many other fields, such as social security, public health, crime suppression, risk management in engineering, warfare, etc.
And in many of these fields I admit that the "American way" has some substantial benefits. In general, however, it is hard to say that "planning for the worst", as we are used to do, is entirely wrong.
Certainly it is more limiting, it has larger costs, it requires more knowledge.
But it is a safer way of living, resulting, in the long term, in better health, longer life, more predictable future. Perhaps less funny, fewer surprises...
Sorry for wandering off topic!
 

Hojo in SC

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You sound like me when I started, and I started; I wanted to know as much as possible and to reduce the risks as much as possible. My solution; read, read, class after class, and read more. I even read the Navy Dive Manual. Do I do "deco stops" not really, but I do make 'safety stops' after I've gone beyond 60 feet.
 

100days-a-year

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I have friends who dive ridiculously and have had 0 consequences after thousands of dives. I have friends who have been bent within NDL and without violating ascent rates.
Safety is relative and subjective. The drive/flight/ boat trip to the divesite is likely the most dangerous part of a dive trip.
 

dmaziuk

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Theoretically speaking, if you make a 30 minute dive to 90 feet breathing air and decide to make a deep safety stop at 30 feet, will you still be on gassing nitrogen? Or off-gassing?

Theoretically speaking it likely does not matter at all because at 30 feet you can't possibly on-gas above Haldane's original 2:1 maximum allowed overpressure ratio. By modern NLD/M0 standards you'd be "safer" by doing the stop at 20 feet, but in practice it won't matter on a "recreational" dive as you won't be down there long enough either way.

Read the DSAT report: you have to keep doing this several times a day for 6 days straight for the slow compartments to show any gas accumulation.
 
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Wow! A huge thank you for the overwhelmingly warm welcome everyone, the solid pieces good advice, and sobering suggestions to focus on other more important things first.

I think without technical dive training, it's not really smart or feasible to do "deco stops" on a rec dive. The main problem I see is that you could potentially consider that the stops can be ignored, since you aren't "actually" in deco. However, in this case then, how do you know if you truly ARE in deco (as in, a direct ascent to the surface is likely to cause injury) or not? Basically, the readout on your computer will no longer reflect reality...
That exact question was a lot on my mind with conservative profiles and with regards to computer selection. Thank you for helping me understand how to think about this. Indeed, I do want a computer that can show SurfaceGF so that I can make rational & informed decisions should I want or need to deviate from the original plan. Though, I think I'd still choose a more conservative high GF for planning and setting the dive profile, and just monitor SurfaceGF closely should I deviate for any reason.

Do you personally feel like the typical 3min @ 5m is insufficient for you? Are you feeling ill at the surface or later in the day? Some red flag like that? If not, I'd say no - all this isn't practical.
Ahh, if didn't feel this way I wouldn't have started this thread :).
Feelings aside, is the standard safety stop insufficient for me? I don't know and don't have the experience to know. I feel tired after diving (probably related to decompression stress), I've never had clinical DCS symptoms, but I also don't have a baseline for what's normal.
I don't think anyone will fault you for having concerns for your own safety, but before diving into deco theory maybe start with more experience and confidence underwater.
That's true for sure!
What triggered me to start this thread was effectively looking for safe/conservative ascend / safety stop stop protocol and curiosity re. what dive computer to buy. I don't think I've quite figured the former based on all the great suggestions so far (beyond maybe slow ascend and 5 minute safety stop to keep it simple), but at least I know I want a computer that's able to show the SurfaceGF and to give me sufficient data to be able to make thoughtful decisions.

If you're actually following agency rec limits your dive profile can look like this |____| and you shouldn't be getting DCS with all the conservatism already applied.
From a overall risk perspective you are spot on. What frustrates me, though, is reading research that in recreational divers following/executing conservative plans, a large (or by memory, even the larger) portion of DCS cases were undeserved. Staying within half of the NDL limit (assuming single depth) seem like a notable risk reduction, but feels quite conservative to be practically enjoyable...

You are a recreational diver. Focus on buoyancy control and dive will within the recreational limits. GF's should be the last item on your mind right now.

Think of it this way, you just learned to drive, you dont need to know how to set up the springs of your car for Daytona.
It's not like I haven't thought about this:) Truth is, I guess I like to overthink things and decompression theory is fascinating so I think I'll end up indulging a bit more in the theory for fun, but follow your advice to spend my energy and efforts elsewhere on actual dives.

I researched and published an article on deep stops for decompression dives. I had a lot of help from renowned decompression expert Dr. Simon MItchell. When I was done, I wanted to write an article on deep stops for recreational dives, but Dr. Mitchell would not help me with it. He said there is not enough research to know one way or the other what to do. I then spent a lot of time researching on my own, and I finally concluded that there was not enough research one way or the other to know what to do.

I am familiar with the research you cite, and you should know that it is not highly regarded. The DAN America's article that originally wrote about it now has a disclaimer saying it does not represent current thinking.

What does have a lot of research behind it is the standard slow ascent--it has been investigated for more than a century. Then safety stops were added, and that made things better. The level of safety associated with slow ascents and safety stops is well-studied, and it is proven to be a very safe procedure.

If you read my article, you will see that deep stops in decompression diving used to be very popular, but more recent research has shown that they are actually harmful because of the added pressure to mid-range tissues. Perhaps a through research study on deep stops in recreational diving may show that it creates the same problem. Perhaps. Perhaps not. As I said before, the only studies that have been done are flawed, so there is no good evidence. to show either a benefit or a harm.
I was reading your article a few days ago and found it (and the linked research) extremely helpful! (Quite excited to see you sharing wise thoughts and suggestion on my thread - thank you!). Though, the more I read, the more I come to the same conclusion as you that there is lack of clarity on optimal protocols for recreational diving (beyond the 3-5 minutes safety stop). Sad and frustrating, given how many people dive recreationally and the accident rates for such divers (admittedly a lot of which are not DCS related).
 
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HomeBarista

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I too am a life long swimmer/triathlete and SCUBA diver. I do not overly concern myself with fear of DCS. At 67 yo and 50 plus years a diver I have never been bent and have done some pretty aggresive diving, no deco and deco adventures. I think you are overly concerned with the possibility of dcs.

I do not agree with setting air and diving Nitrox. Instead just set your computer to a more conservative setting for the appropriate Nitrox mix you are using.

I do not think you should create your own deco profiles for no deco dives.

I do a solid 15-20 feet safety stop (5 minutes or Adaptive) and on deep dives (greater than 80 feet) that approach NDL I may do a half maximum depth "pause" of one minute circumstances allowing.

My new computer is the Shearwater Peregrine. I think you need one.

James
Thank you, James! Glad to hear you've been dodged the bents and are active in both diving and triathlon at 67. Respect! I hope to be able to replicate this at that age.
Fully agree with you on not using air for nitro as an added safety protocol (be it a good one as it adds conservatism) as I would prefer having clean data and there seem to be better ways to add conservatism that don't involve obscuring information that may turn out useful.
Thank you for sharing your safety / ascend protocol too, which seems quite practical.

Don't lie to your computer. If you are using a computer that allows you to set gradient factors, just choose a gradient factor that keeps you far enough away from NDLS to be comfortable. A GF high of 70 is very conservative, and you can start there. (GF lows don't matter in NDL diving.)
yeah, fully with you! Don't lie to the computer! It's there to give you data.
Btw, do you know if the 50/70 or 50/75 GFs used by Powell and Mitchel are for their recreational or tech dives?

Yep, GF high of 75 is already more conservative than my Suunto Zoop Novo on the first dive.
I recently realized the same when playing with dive planner and comparing to my Suunto Zoop Novo (well, a friends Zoop, that I'm borrowing. Still have to get a comp of my own.)
Suunto's seem to have some added conservatism for repetitive dives, but not sure if that's backed by research. fwiw, it seems that neither RGBM nor Buhlmann are backed with a lot of research on repetitive dives, such as the ones one might do a week-long diving vacation.

Regarding the slowing of your ascent, I don't think a lot of divers appreciate the magnitude of this adjustment.
Edited (to fit in word limited): Guidelines on slow ascent follow...
As much as I appreciate the slow ascent guidelines (and a huge thank you for posting the recommended ascent rates), my hypothesis is that recreational divers don't appreciate it because it hard to execute and track, it takes skill and concentration. As a new diver myself, I kind of like the allure of "get to 15, hang out there for 5+ minutes, hopefully see some fish" and then go out. Definitely more enjoyable in my book than constantly staring at the computer and micromanaging the ascent. But I guess practicing it would do wonders for my buoyancy, so I know what I'm doing on my next dives.

You sound like me when I started, and I started; I wanted to know as much as possible and to reduce the risks as much as possible. My solution; read, read, class after class, and read more. I even read the Navy Dive Manual. Do I do "deco stops" not really, but I do make 'safety stops' after I've gone beyond 60 feet.
Haha, yes, you've got the theoretical bent, too (no pun intended!). I've also gone pretty deep down the rabbit hole already. But hey, reading and expanding our knowledge is fun. And to be honest, I wouldn't be opposed if all the reading lead me on the path of hanging at 15-20 feet for 5 minutes.


Btw, any suggestions how to get a discount on a Shearwater Peregrine?
If this is helpful, I reside in the US and travel a lot.
 

rongoodman

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This concept that deco is "technical" is typical of American for-profit training agencies.
The usual definition of a technical dive seen around here is a dive in which one no longer has direct access to the surface, due to either a hard(cave/wreck) or soft(deco)ceiling. I'm not sure what "for profit training agencies" have to do with it.
 

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I do remember my first deco dive. With all the "no deco" mutterings of the recreational dive community, actually doing some decompression becomes a really big thing. All we did was a 30m/100ft dive for about 40 mins on the bottom with 10 mins of decompression on backgas.

The 10 mins spent at decompression was really disconcerting; can I feel the bubbles escaping, what if I can't hold my stop; OMG I'm going to get bent...

It's like being told buy the wizened experts "ooh-arrrh, there be dragons behind that there door".

Nowadays I can't remember my last non-deco dive (aside from 10m/30ft lake dives). Must be the effect of the bubbles on my brain :wink:
 
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