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View Full Version : Isn't Nitrox, trimix and diving below 130ft really commercial diving without the $$$$



WaScubaDude
09-13-2007, 22:04
I am back to diving after two decades off. What is now called "tech" diving is what we called commercial diving.

I put together an analogy that goes like this:
In rock climbing people who hike the trail and look at the view are like snorkelers...you could get hurt but not likey.
People who top rope into bomb proof protection are like OW divers, you can get hurt but usually because you made a big mistake.
People who lead climb and set pro are like Advanced open water or penetration divers. One good f-up and you will get hurt or die.
People who free climb without pro or rope are like "tech" divers, very calculated very smart, and it's only a matter of time before they die.

If you think I am absurd just google "Johny long blades" or read the scuba death board. "Tech" divers are some of the very best divers no doubt but also the ones making calculations about what could have been done, when the truth is; diving is dangerous and "tech" diving is very dangerous.

Who is off their rocker? You or me?

in_cavediver
09-15-2007, 21:27
I am back to diving after two decades off. What is now called "tech" diving is what we called commercial diving.

I put together an analogy that goes like this:
In rock climbing people who hike the trail and look at the view are like snorkelers...you could get hurt but not likey.
People who top rope into bomb proof protection are like OW divers, you can get hurt but usually because you made a big mistake.
People who lead climb and set pro are like Advanced open water or penetration divers. One good f-up and you will get hurt or die.
People who free climb without pro or rope are like "tech" divers, very calculated very smart, and it's only a matter of time before they die.

If you think I am absurd just google "Johny long blades" or read the scuba death board. "Tech" divers are some of the very best divers no doubt but also the ones making calculations about what could have been done, when the truth is; diving is dangerous and "tech" diving is very dangerous.

Who is off their rocker? You or me?

First, commercial diving differs from rec/tec diving in the goal. Specifically, tec diving is done at great personal expense for pure recreation and enjoyment. Commercial diving is done for a paycheck.

I think you miss the a bit more on the analogies as well. Tec divers are very risk aware, more so than your average advanced OW diver. Your average tec diver will plan for and mitigate as many risks as possible on a given dive, even if its only to 130'. BTW, any real penetration diving is tec not rec.

Here's another set of analogies:

Walk in the park = snorkeling
day trip hikers = OW
Backpackers = AOW/Rescue
expeditions = Tec

Essentially, with each level, more complications and planning are required. Risk also increases but methods of mitigation are introduced as well. Ultimately, its up to each individual to determine their personal risk tolerance.

Flatliner
09-15-2007, 21:58
Much better analogie Cavediver

WaScubaDude
09-17-2007, 13:10
I like the simpler analogie, but I am not sure if it conveys all the complexities it should. How do you take into account the dangers of mixed gas dives, multiple mixed gas dives with planned deco, mixed gas penetration or deep dives etc.

Aussie
09-17-2007, 17:11
I think things have changed alot in the 20 years you have been out of the water.

Aussie

in_cavediver
09-17-2007, 19:58
I like the simpler analogie, but I am not sure if it conveys all the complexities it should. How do you take into account the dangers of mixed gas dives, multiple mixed gas dives with planned deco, mixed gas penetration or deep dives etc.

The complexities are just that, complexities. There is a reason some divers spend up to 10 times as much time planning a dive as doing the dive. With more complications come more oppertunities for problems and therefore more risk.

Now, for dangers. Essentially, they all are the same. You can't breathe water so you have to make sure you have something working to breathe. You can't overstay a limit without hitting a bailout plan (be it NDL or planned deco) and hitting a bailout means increasing risk. Divers need to know the procedures to properly use all of their equipment and its bailouts, be it CESA or lost deco gas. And last but not least, your in a foriegn environment, your instincts work against you and you have to control fear, anxiety, exitement and adreline to maintain mental control and thus ensure your safety. Thats it, no difference in core needs, just the level of complexity.

Again, nitrox, trimix, staged deco, rebreathers, overheads and excessive depth are only tools and environments to dive. The knowledege, techniques and procedures for mitigating risks exist and are taught for operating in these environments.

In my opinion, some of the dives I've done to 130-150 are safer than many 'deep' dives done by 'rec' divers purely based on extra equipment protocols and procedures I use. (and I likely surfaced with a lower N2 saturation as well)

WaScubaDude
09-18-2007, 01:22
I think things have changed alot in the 20 years you have been out of the water.

Aussie

Its funny because some things have changed and some have not. I feel like I have learned alot from the Q & A on this board and other research that I have done. If I sound a cautionary note don't take it personaly. My question and the discussion that followed is part of my learning and I trust will be part of others learning as well. For me I am restling with the risks inherent in this sport. Finding ways to enjoy the sport and live to dive another day.

ianr33
09-18-2007, 08:39
Aussie[/quote]

For me I am restling with the risks inherent in this sport. Finding ways to enjoy the sport and live to dive another day.[/quote]

I think everybody does that,whether they are taking an OW class or extending the line in Wakulla.

IMHO if you are scared of a particular dive then you should not do it. Mild apprehension is O.K. and is probably a good thing as it keeps you focussed,but once that crosses over into fear you need to rethink what you are doing.

Bill22
09-20-2007, 03:19
Walk in the park = snorkeling
day trip hikers = OW
Backpackers = AOW/Rescue
expeditions = Tec

Nice analogy.... I like it :-)

pnevai
09-20-2007, 21:30
In the end, which group, commercial or tek divers have a greater fatality rate? I think you will find that Tek divers die more often. The main reasons for this is mainly that both have similar hazards, and complexity but the Commercial Diver has automatic safe guards, there are OSHA standards that have to be met at the dive site, recompression facilities are usually right there on site and a paid surface crew to keep an eye on things. Also there is more safety technology involved, like UW communications systems and communications links to the top side that are just out of reach financially out of reach to the TEK diver.

Commercial divers usually have a far larger safety net in which to work.

WaScubaDude
09-23-2007, 23:54
In the end, which group, commercial or tek divers have a greater fatality rate? I think you will find that Tek divers die more often. The main reasons for this is mainly that both have similar hazards, and complexity but the Commercial Diver has automatic safe guards, there are OSHA standards that have to be met at the dive site, recompression facilities are usually right there on site and a paid surface crew to keep an eye on things. Also there is more safety technology involved, like UW communications systems and communications links to the top side that are just out of reach financially out of reach to the TEK diver.

Commercial divers usually have a far larger safety net in which to work.

Very well put.
And I would add; diving is dangerous, tech diving is more dangerous.

CompuDude
09-24-2007, 16:35
In the end, which group, commercial or tek divers have a greater fatality rate? I think you will find that Tek divers die more often. The main reasons for this is mainly that both have similar hazards, and complexity but the Commercial Diver has automatic safe guards, there are OSHA standards that have to be met at the dive site, recompression facilities are usually right there on site and a paid surface crew to keep an eye on things. Also there is more safety technology involved, like UW communications systems and communications links to the top side that are just out of reach financially out of reach to the TEK diver.

Commercial divers usually have a far larger safety net in which to work.

Very well put.
And I would add; diving is dangerous, tech diving is more dangerous.

I think if you truly analyze the accidents and causes behind them you'll find that most tech diving accidents are either lack of training, gross mistakes (such as ignoring rules you learned in training), and/or insufficient training.

There are a lot of people with marginal technical diving training and skill levels taking on more than they can chew. If you eliminate those Darwin Award winners, I suspect the number of tech diving deaths vs. successful dives would drop a LOT slower than the risks of commuting for work via the freeway.

In addition, there are tech dives, and there are TECHNICAL EXPEDITIONS (emphasis deserved). The latter obviously carries with it considerably more risk than your average "run of the mill" technical dive, say, down to a 150' wreck on trimix with little penetration. Technical diving runs the gamut from 100'+ on trimix to 4000' into a cave to 300'+ down deep into the Andrea Doria. And yet it's call called technical diving and painted with the same implications? I don't think that's fair.

in_cavediver
09-24-2007, 17:17
An interesting statistic to look at is the rate of incidents/fatalities based on training. DAN publishes this each year. Over the past years I've looked at it, the two spikes are at the OW-OW student level and the DM-Instructor level. I know this doesn't take per capita dives done for each level or any other massaging but in raw form, more OW divers die than tec divers each year. Given that, in raw numbers, OW divers are just plain dangerous right???? (loads of sarcasm here, we all know its not true)

Now, Compudude brings up a very interesting question. How do you differentiate rec from tec? How do you define a qualified diver for a dive? And lastly, where do you draw the line from 'mainstream' to 'exploration' diving? The answers to these questions really skew the resultant opinions on the safety of 'tec' diving.

I'd argue your average mainstreamn tec diver, while facing increased risk on some dives, has a better track record safety wise than your average mainstream rec diver. We will never know if that true simply because there is no substantial data to prove it one way or another. Just gut feelings.

As I said before, diving at any level is really an exercise is risk management with the risk benefit analysis defining the go-no go choice. The more risk tolerant you are and the more risk management procedures you know/have mastered, the more complicated the dive you can do within your risk envelope. Its not a competition, there aren't medals for achieving more, its just recreation. Whatever makes you happy makes you happy, be it a 20ft reef dive or a 250' wreck dive.

cummings66
09-24-2007, 22:05
You know, WaScubaDude always brings up interesting questions and get some good interaction going via that initial question.

It does seem things have changed in the 20 years that have gone by.

I'm curious though, did you do a refresher course or just retake a class? Just wondering due to some of the analogies you've used, they seem dated when you're not that old. I say that because we're the same age and I don't think I'm old yet. I'm still young enough to have fun, but old enough to know the risks.

At any rate IMO this is how my technical diving is going to be done. First, no penetration dives of any kind until my daughter is out of the house and married off. Can you guess why? I'm minimizing risk, I know theres risk in all things, but certain aspects carry more even if you're trained in doing it the right way.

WaScubaDude
09-25-2007, 01:16
You know, WaScubaDude always brings up interesting questions and get some good interaction going via that initial question.

It does seem things have changed in the 20 years that have gone by.

I'm curious though, did you do a refresher course or just retake a class? Just wondering due to some of the analogies you've used, they seem dated when you're not that old. I say that because we're the same age and I don't think I'm old yet. I'm still young enough to have fun, but old enough to know the risks.

At any rate IMO this is how my technical diving is going to be done. First, no penetration dives of any kind until my daughter is out of the house and married off. Can you guess why? I'm minimizing risk, I know theres risk in all things, but certain aspects carry more even if you're trained in doing it the right way.

At 41, I have lived alot and done alot. I don't feel old at all, but as I look back I hope I am learning and growing. I speak up here in part because I know the value of a fresh perspective. I do business consulting and sometimes the newest person has the best and freshest perspective, they haven't been at it soo long as to shrug their shoulders and say "that's the way it has always been done." I really don't mind people taking risks as long as they truely understand what is at stake and the likely hood they may not make it back.

The anolgy I used comes from experience. I was rock climbing in BC, I was top roped, and an amercian woman was free climbing (no rope, no pro) I talked with her a bit and she said her longtime boyfriend died free climbing just 2 months prior. She was at this rock face with an australian guy she met traveling. They were both free climbing. There was a tough move about 12ft off the ground she tried it and failed scraping her knee and chaffing on someone elses rope. He tried the same move and fell 12 ft with his head landing 4 inches from a large rock. It really made me think that people do not asses risk well, many live in a delusion about how good they are and how it hasn't happened to them, so it won't ever.

You mentioned your daughter, I have a five year old daughter as well. This has given me even more perspective reguarding risk. I want to be around to teach her diving and to see her experience the joys under the sea.

My questions are really more for my learning, but I also feel a deep kindered spirit with other divers. I read the Scuba Death reports and I don't want to see more senseless and ignorant deaths.

I may seem old or out of touch but I think you would find me an excellent diver and a fun buddy to dive with. If my questions challenge you and other very experienced divers to think a bit, to be even a bit better, a bit safer and to live and dive till we are too old to drop into the deep blue, well thats just fine with me.

cummings66
09-25-2007, 12:18
I wasn't meaning that you seem old, more that your comparisons/background seems dated. IE you basically believe that a tech diver is so cutting edge and risky that they WILL die in the end no matter what they do. That's an old analogy that doesn't really apply now due to improved gear and technique. That's what I'm getting at, not you being old but your viewpoints and observations are based on facts from when you first got trained and don't consider today's dive environment.


People who free climb without pro or rope are like "tech" divers, very calculated very smart, and it's only a matter of time before they die.

quasimoto
09-25-2007, 14:17
Man there is a lot to digest in this thread. Good thread and information.

One question that was kinda skipped over was, where do you draw the line for tec versus rec. Personally once you go into either advanced nitrox w/o deco or into ANY deco class you are in the tec world. I am getting myself ready to really look in to deco and it seems that most people fall off at that point.
I feel that this is all upon the person doing it as to if they are ready or not. I can admit that I am not ready skill wise for tec. I will work on this and then and not till then I will continue my education. If I never feel ready to do it then I wouldn't do deco. I'm sure that there are those that don't do this and they just might be our Darwin people.
If the student really isn't ready then I think that the instructor shouldn't allow the to be certified. From what I am ready on most LDS pages that teach tec they say that they reserve the right to either not accept the student or to fail them if their skills aren't sufficient to pass. Personally this need to be industry wide but we know it isn't. Lets face it most divers that and LDS certifies goes to warm waters once a year.

I like looking at the stats from DAN but I think they are lopsided. Like metntioned above there is just no way to really do a geat job on it.

Iceman
09-25-2007, 14:24
Aren't the terms "Rec" and "Tec" really broad identifiers that people can use for self identification? They aren't really precise definitions that can functionally serve as pigeon holes for people.

Isn't the only firm differentiation between Commercial and Non-Commercial. One gets a paycheck, the other doesn't. So, on a dive to 30' on a reef one person who is doing it for fun is non-commercial while the other who is getting paid for pictures is Commercial.

One thing, though, I think is common among "Tec Diving" is the propensity to use less than optimal equipment for certain kinds of dives. One example I have in mind is the person who uses a rebreather to do as recovery task at 300' when a more appropriate equipment selection would be something that is common in the commercial world. The former is risky while the latter is just normal industrial practice that is fairly closely regulated.

ianr33
09-25-2007, 14:31
One question that was kinda skipped over was, where do you draw the line for tec versus rec.

My question would be not so much where do you draw the line but why even attempt to draw it.

Its all just diving,some is deeper and longer than others.

2 divers do the same dive. Diver #1 has an Aeris computer,diver #2 has a Suunto. Diver #1 has a NDL dive. Diver #2 has 2 minutes deco. Does that mean diver #2 is a Technical Diver?

"tech" is a pretty meaningless,marketing driven phrase.


The standard definition of a technical dive is something along the lines of "Any dive deeper than 130 feet or any dive where you can not make an immediate ascent to the surface.(Due to a "soft" overhead i.e. deco requirement or a hard overhead i.e. rock or steel )

quasimoto
09-25-2007, 15:21
One question that was kinda skipped over was, where do you draw the line for tec versus rec.

My question would be not so much where do you draw the line but why even attempt to draw it.

Its all just diving,some is deeper and longer than others.

2 divers do the same dive. Diver #1 has an Aeris computer,diver #2 has a Suunto. Diver #1 has a NDL dive. Diver #2 has 2 minutes deco. Does that mean diver #2 is a Technical Diver?

"tech" is a pretty meaningless,marketing driven phrase.

The standard definition of a technical dive is something along the lines of "Any dive deeper than 130 feet or any dive where you can not make an immediate ascent to the surface.(Due to a "soft" overhead i.e. deco requirement or a hard overhead i.e. rock or steel )

You have a good point about the line but yes I think there needs to be something. I don't know that it needs to be set in stone though. Actually from what I am seeing and from talking with others that are looking at doing deco there is already a big gap in training. This may not always be true, don't know.

If diver number 2 knows what he is doing then I think by "most standards" (whatever that may be) then yes he is doing a tec dive.

Personally I don't agree with your definition of tec simply because in AOW you can do 130' so since I have done 135' does that mean that I am tec? Pesonally I don't think of it that way. There is really no ideal place for everyone to "draw the line". Deco just seems like a reasonable place to me.

ianr33
09-25-2007, 15:34
But what is deco?

Is it one minute showing on a Suunto computer or is it deco according to the Navy Tables?
19 minutes at 100 feet is not a deco dive according to my computer and also to PADI. It IS a deco dive on V-Planner

Its not so much a "line" but a very broad gray area.

And what is the difference between a deco stop and a mandatory safety stop?

Bill22
09-25-2007, 16:12
You know, WaScubaDude always brings up interesting questions and get some good interaction going via that initial question.

It does seem things have changed in the 20 years that have gone by.

I'm curious though, did you do a refresher course or just retake a class? Just wondering due to some of the analogies you've used, they seem dated when you're not that old. I say that because we're the same age and I don't think I'm old yet. I'm still young enough to have fun, but old enough to know the risks.

You're right he does always bring up interesting questions that get people to think and generates a good discussion. I think some of us learn a lot from these discussions from more experienced divers. I think that's a good thing. I know I've learned some things here (including from you ;-)) and that has been a big help in shortening my learning curve as I get back up to speed :-) I'm even making some changes in my gear configuration based on those discussions which might potentially save someones life someday.

I hope he won't mind if I share some info from a PM. I PM'd him after one of his earlier posts. I was curious how he had managed to cram so many dives into what appeared to such a short period. He PM'd me back and essentially said it was a fair question and answered me no problem. I can only say "Wow!" lucky guy!

Just to clarify for everyone else, he left Washington 20 years ago and just got back "there". He was away from Washington for 20 years... his break from diving although long was shorter than that. He's been diving down in the Carribbean for the last 4 years. For him (and he can correct me if I'm wrong :-)) that may still feel like he's just getting back into it. Only because he had done so much when he was younger. Or maybe he just didn't want everyone else to be jealous that he got to spend four years in the Carribbean ;-) For most of the rest of us I don't think we would consider it "just" getting back into it :-)

He's crammed a lot into his life and he's seen a lot (as a lot of us here on the board have). If he's gotten people (not neccesarily the ones directly involved in the discussion, but other's who are reading it) to think about risks and the discussion by other experienced people (ie.. the rest of you guys ;-)) gives them something to think about it... then I think that's a good thing too :-)

A big thanks to everyone... very interesting discussion :-)

in_cavediver
09-25-2007, 17:35
One thing, though, I think is common among "Tec Diving" is the propensity to use less than optimal equipment for certain kinds of dives. One example I have in mind is the person who uses a rebreather to do as recovery task at 300' when a more appropriate equipment selection would be something that is common in the commercial world. The former is risky while the latter is just normal industrial practice that is fairly closely regulated.

One key here that is yet to be defined is 'optimal'. For a working dive at 300', where your welding, turning valves, a hard hat is a good tool. For an exploration of a shipwreck or penetration of a cave, that same hard hat is a very poor choice. Actually, for a 300' deep, long distance cave penetration dive there isn't much in the commercial world capable of this, much less a manned version.

Gear is tools to accomplish a goal. You have differing critera for optimal based on the specific goal and there is a huge difference between commercial and sport diving here in the goal section. I'd personally take a CCR for a 300' dive over the hard hat surface supplied walk on the bottom rig used commercially simply because the CCR is a hell of lot more portable and flexible. See - different critera for optimization yielding different optimal solution.

As others have said, the lines between rec and tec are hard to draw and usually very gray. The line between commercial and tec is usually very distinct as the goals of both are quite different. As such, the gear used and protocols are also quite different.

quasimoto
09-25-2007, 20:12
OK so the there is no line and it is more of a grey area...so be it. But deco is deco when it is done intentionally. Whatever table or computer you follow.

ianr33...in theory there isn't a difference between a "safety" and a "deco" stop. They are both doing the same. Yes one of them is for safety and one is more mandatory but they are all the same in theory.
You say mandatory safety stop in your post. I will assume that you are talking about a stop done on..say a 50' dive that your computer or table doesn't say that you are in deco.

Iceman
09-25-2007, 20:41
OK so the there is no line and it is more of a grey area...so be it. But deco is deco when it is done intentionally. Whatever table or computer you follow.

ianr33...in theory there isn't a difference between a "safety" and a "deco" stop. They are both doing the same. Yes one of them is for safety and one is more mandatory but they are all the same in theory.
You say mandatory safety stop in your post. I will assume that you are talking about a stop done on..say a 50' dive that your computer or table doesn't say that you are in deco.

Perhaps it would be more precise to say that All Dives Are Decompression Dives. Then to elaborate that for some dives a person may reasonably account for the decompression obligation with a standard stop, called a Safety Stop. For other dives the decompression obligation is deemed more critical and must be accounted for with a stop tailored to the dive profile.

ianr33
09-25-2007, 22:40
ianr33...in theory there isn't a difference between a "safety" and a "deco" stop. They are both doing the same. Yes one of them is for safety and one is more mandatory but they are all the same in theory.
You say mandatory safety stop in your post. I will assume that you are talking about a stop done on..say a 50' dive that your computer or table doesn't say that you are in deco.

Safety stops are optional. Do them if conditions allow.
I am going from memory here as it is a long time since I have used PADI tables but IIRC any dive within 3 letter groups of an NDL or below 100 feet requires a MANDATORY SAFETY STOP ? This amuses me because a mandatory safety stop is clearly a deco stop. However it is not politically acceptable to use the D word for a recreational diver hence the bizarre "mandatory optional stop" :smiley36:

The more I learn about deco the more I realise it is as much voodoo magic as it is science. Most tables agree that the NDL on air for 100 feet is around 20 minutes.
If you do 25 minutes at 100 feet you will most likely be just fine (Thats what the Navy Tables allow) Even do 30 minutes at 100 and if you are reasonably fit you will probably get away with it. Pick a day when the planets are not in alignment though and you might get bent doing 15 minutes at 100.

Seems to me a lot of divers are quite happy to follow their computers to within a minute or 2 of NDL thinking they are perfectly safe,but as soon as they step over that line OMG,I'm in DECO!!!!!!!!!!!
This makes no sense. Computers give a false sense of No Deco/Deco. In reality it is a very,very wide gray area.

I do agree though that once you start planning for precise deco stops rather than "3-5 minutes somewhere between 25 and 10 feet" then you have crossed over into technical diving (much as I dislike that phrase)

WaScubaDude
09-25-2007, 23:55
ianr33...in theory there isn't a difference between a "safety" and a "deco" stop. They are both doing the same. Yes one of them is for safety and one is more mandatory but they are all the same in theory.
You say mandatory safety stop in your post. I will assume that you are talking about a stop done on..say a 50' dive that your computer or table doesn't say that you are in deco.

Safety stops are optional. Do them if conditions allow.
I am going from memory here as it is a long time since I have used PADI tables but IIRC any dive within 3 letter groups of an NDL or below 100 feet requires a MANDATORY SAFETY STOP ? This amuses me because a mandatory safety stop is clearly a deco stop. However it is not politically acceptable to use the D word for a recreational diver hence the bizarre "mandatory optional stop" :smiley36:

snipped...

If I can give it a go. Having never done a deco stop.

A safety stop can be mandatory, that is, insited upon by the DM. On my tropical cattle boat dives the DM says you must make a 3 (or 5) minute safety stop. It is not because the divers are over NDL or even because anyone has exces nitrogen to breath off for certain. Safety stops are done most commonly 1) To try to head off rapid assents to the surface 2) to round up the whole group to surface together 3) to help divers work on bouyancy and at the same time let DMs assess how good each diver is for inclusion on tougher dives 4) lastly to provide a larger margin of safety for those that may actually need to breath down their nitrogen levels. Read(over weight, out of shape, swam too hard, freaked and breathed very quickly) events that may have put them over acceptable levels in their system.

In Tech diving a Deco stop is done because charts, formulas in computers, and dive planning tells you that at x ft for x minutes, breathing x mix, the average diver will have excess nitrogen in his body that MUST be removed prior to surfacing, or injury or death will likely result.

IMHO accidents occure in Tech diving often because the injured diver did not fit the profile of the subjects used to establish the formulas. To state it simply; the charts are largely based on data from Navy divers, most usually young, fit and male. Divers who do not fit this profile run a greater chance of injury and death by using the existing formulas and not adding great margins of safety. I think new charts will be developed in time, the unfortunate thing is the system currently in use is a "management by exception" (Another woman dies tech diving or another everweight 48 yr old dies tech diving and maybe now we will change the charts and formulas.)

pnevai
09-26-2007, 00:42
ST Fish Says

ianr33
09-26-2007, 08:47
lastly to provide a larger margin of safety for those that may actually need to breath down their nitrogen levels. Read(over weight, out of shape, swam too hard, freaked and breathed very quickly) events that may have put them over acceptable levels in their system.

In Tech diving a Deco stop is done because charts, formulas in computers, and dive planning tells you that at x ft for x minutes, breathing x mix, the average diver will have excess nitrogen in his body that MUST be removed prior to surfacing, or injury or death will likely result.


After just exceeding deco limits the AVERAGE diver would be just fine to surface immediately. However, 1% of divers (guessing numbers here) would show symptoms.Not doing a large amount of deco (say 30 mins?) Is very likely to hurt and missing a couple of hours would almost certainly kill you but a minute or 2 is PROBABLY not going to have any bad affects.

I agree that being out of shape and/or overweight increases susceptibility to DCS but your other examples (swimming too hard/breathing too quickly) do not. This seems to be a common misconception.
Overexertion is not good for lots of reasons (CO2 retention,Oxygen toxicity,Narcosis) but DCS is not one of them

ianr33
09-26-2007, 09:02
IMHO accidents occure in Tech diving often because the injured diver did not fit the profile of the subjects used to establish the formulas. To state it simply; the charts are largely based on data from Navy divers, most usually young, fit and male. Divers who do not fit this profile run a greater chance of injury and death by using the existing formulas and not adding great margins of safety.

That may have been true once upon a time but not today.The deco software I use is V-planner
http://www.hhssoftware.com/v-planner/ This has LOTS of interesting reading
Considering a dive to 100 feet for 20 minutes. With PADI this is NDL.
V-Planner set on zero conservatism (for 20 year old athletes) asks for 6 minutes of deco stops .With conservatism on +5 (cold water,unfit,previous DCS) it needs 17 !!! minutes of stops.

My points here are:
1)The profiles of "technical" divers are actually more conservative than the far edge of recreational tables.Sometimes a lot more conservative.
2)It is up to the individual diver to decide how much conservatism they want to use. Just because my Aeris computer has just cleared a deco obligation does not mean I am now heading for the surface !!

If you are doing 60 feet for 30 minutes then none of this matters,but once you get somewhere near the fuzzy deco area the thinking diver needs to consider these issues.

WaScubaDude
09-26-2007, 09:32
lastly to provide a larger margin of safety for those that may actually need to breath down their nitrogen levels. Read(over weight, out of shape, swam too hard, freaked and breathed very quickly) events that may have put them over acceptable levels in their system.

In Tech diving a Deco stop is done because charts, formulas in computers, and dive planning tells you that at x ft for x minutes, breathing x mix, the average diver will have excess nitrogen in his body that MUST be removed prior to surfacing, or injury or death will likely result.


snipp...
I agree that being out of shape and/or overweight increases susceptibility to DCS but your other examples (swimming too hard/breathing too quickly) do not. This seems to be a common misconception.
Overexertion is not good for lots of reasons (CO2 retention,Oxygen toxicity,Narcosis) but DCS is not one of them

Is this because nitrogen absorption is at a fixed rate for a given diver no matter how much they breath? No difference between a skip breathing diver going thru 600psi and the same diver breathing really hard and using 1800psi for the same depth same bottom time? Thanks for the info.

Oh and what of the Safety Stop VS Deco stop argument?

ianr33
09-26-2007, 09:45
Is this because nitrogen absorption is at a fixed rate for a given diver no matter how much they breath? No difference between a skip breathing diver going thru 600psi and the same diver breathing really hard and using 1800psi for the same depth same bottom time? Thanks for the info.

Oh and what of the Safety Stop VS Deco stop argument?

Correct. The only thing that matters is the pressure of the nitrogen and that is the same no matter how fast/slow you breathe.

Overexertion at great depths (>200 feet??) may well be a factor in DCS due to it forming microbubbles that act as nuclei for bubble formation.
Howard Hall got bent filming "Coral Reef Adventure"? he put it down to swimming hard at 300 feet while dragging an iMAX camera.
Not an issue at recreational depth though.

Safety Stops/Deco Stops ? Yes,basically the same thing.Certainly serve the same purpose.

PhantomCat
09-27-2007, 05:13
Correct. The only thing that matters is the pressure of the nitrogen and that is the same no matter how fast/slow you breathe.

Actually no, Free diver hyperventalate to A)increase o2 in lungs B) lower CO2 in blood- so exertion at any depth CAN affect gas levels. The effects are not generally detrimental until deeper depths like you mention below.

Overexertion at great depths (>200 feet??) may well be a factor in DCS due to it forming microbubbles that act as nuclei for bubble formation.
Howard Hall got bent filming "Coral Reef Adventure"? he put it down to swimming hard at 300 feet while dragging an iMAX camera.
Not an issue at recreational depth though.

Safety Stops/Deco Stops ? Yes,basically the same thing.Certainly serve the same purpose.[/quote]

In recreational diving most peole can safely off gas enough of the excess nitrogen built up to end the dive safe just be adhearing to the proper accent rate. The safety stop is a extra margin of safety built into the dive table to account for different situations/people. The Deco stop is REQUIRED to safely end a dive in tech and commercial diving. Because of depth/gas mixture and time at depth the nitrogen bulid up will not off gas enough during a straigh accent, deco stops allow that to happen as predetermined safe intervals. There are a few situations in commercial diving when the diver does a "Sur-D O2" or surface decompression on 100% O2 (hyperbaric chamber) This allows them to complete the required decompression without having to sit in cold or rough waters for long periods of time.

fire diver
09-27-2007, 08:25
Actually no, Free diver hyperventalate to A)increase o2 in lungs B) lower CO2 in blood- so exertion at any depth CAN affect gas levels. The effects are not generally detrimental until deeper depths like you mention below.


But that still has no affect on DCS in relation to nitrogen buildup. Exertion at depth does not change how much gas your body loads up. But as stated earlier in may very well affect how that pulmonary dissolved gas acts.

FD

ianr33
09-27-2007, 08:37
Is this Scubatoys or Freedivertoys ??

PhantomCat
09-29-2007, 06:36
Actually no, Free diver hyperventalate to A)increase o2 in lungs B) lower CO2 in blood- so exertion at any depth CAN affect gas levels. The effects are not generally detrimental until deeper depths like you mention below.


But that still has no affect on DCS in relation to nitrogen buildup. Exertion at depth does not change how much gas your body loads up. But as stated earlier in may very well affect how that pulmonary dissolved gas acts.

FD
During training a diver will learn all about the bends or decompression sickness [DCS]. Nitrogen, absorbed at depth, comes out of the tissues too quickly and forms bubbles. These can go anywhere in the body and cause a broad range of symptoms related to where in the body they are. The most important thing a diver can remember is that the bends does not only occur if they have a rapid ascent from a dive. There are many factors than can increase nitrogen loading or decrease off-gassing at the end of a dive. Increased exertion, dehydration, a saw-tooth profile dive and menstruation are a few of the factors. http://www.londondivingchamber.co.uk/index.php?id=advice&page=5
While I agree this needs more studying done on it, exertion does affect N2 upload. At diver breathing heavy from work (current or whatever) will reach a point of saturation faster than a diver who isn't.

fire diver
09-29-2007, 08:24
I guess you and I are going to have to agree to disagree. Because when you are talking about gas saturation of a liquid, I don't care how fast you throw the gas at it. It can only absorb a finite amount.

FD

PhantomCat
09-29-2007, 09:07
Awww cmon! Don't give up on me so easy. I find this particular subject interesting. There are so many differing thoughts. I actually do not totally disagree with you. The Gas laws are absolute. Your body can only absorb N2 so fast UNLESS the pressure gradient changes. (partial pressure or Dalton's Law) So why does almost all dive related material mention heavy exertion as a factor nitrogen loading. Why is the so much anticdotal documentation of excertion causing what appears to be a DCS event AT depth? I mean this is a direct cut and paste from a reputable dive medicine facility! Doesn't that warrent some open debate/discussion. I mean this is the information going out to new divers, it can't be toatally unfounded right?

The information out there on this is about as clear as mud, and you get as many different answers as the number of divers you talk to, both old and new.

So I guess the question left to ask here is do you think that by exerting yourself you are increasing the pressure gradiant? Or are all these supposed experts wrong. Oh Duke Universtiy did a study that makes this claimm too, when I find the artical again I will give you the link if you want.

in_cavediver
09-30-2007, 09:17
Awww cmon! Don't give up on me so easy. I find this particular subject interesting. There are so many differing thoughts. I actually do not totally disagree with you. The Gas laws are absolute. Your body can only absorb N2 so fast UNLESS the pressure gradient changes. (partial pressure or Dalton's Law) So why does almost all dive related material mention heavy exertion as a factor nitrogen loading. Why is the so much anticdotal documentation of excertion causing what appears to be a DCS event AT depth? I mean this is a direct cut and paste from a reputable dive medicine facility! Doesn't that warrent some open debate/discussion. I mean this is the information going out to new divers, it can't be toatally unfounded right?

The information out there on this is about as clear as mud, and you get as many different answers as the number of divers you talk to, both old and new.

So I guess the question left to ask here is do you think that by exerting yourself you are increasing the pressure gradiant? Or are all these supposed experts wrong. Oh Duke Universtiy did a study that makes this claimm too, when I find the artical again I will give you the link if you want.

I think there is a slight disconnect here. First, in general terms, N2 loading in tissues behaves like the gas laws describe. I am sure there are a few subtle biochemical changes associated with exertion that modify the uptake rates but that isn't the real reason why exertion is bad for DCS.

Exertion as per DCS risk is better explained in the bubble models. IE, for a given N2 loading, what is the size and numbers or bubbles produced. Exertion lead to more micro bubble nuclei and hence, the potential for more bubbles, even if the N2 loading is within tolerance for a tissue model.

Either way, exertion at depth is bad for LOTS of reasons.

elijahb
05-10-2008, 12:05
Much better analogie Cavediver
Yeah It makes more sense

elijahb
05-10-2008, 12:29
Awww cmon! Don't give up on me so easy. I find this particular subject interesting. There are so many differing thoughts. I actually do not totally disagree with you. The Gas laws are absolute. Your body can only absorb N2 so fast UNLESS the pressure gradient changes. (partial pressure or Dalton's Law) So why does almost all dive related material mention heavy exertion as a factor nitrogen loading. Why is the so much anticdotal documentation of excertion causing what appears to be a DCS event AT depth? I mean this is a direct cut and paste from a reputable dive medicine facility! Doesn't that warrent some open debate/discussion. I mean this is the information going out to new divers, it can't be toatally unfounded right?

The information out there on this is about as clear as mud, and you get as many different answers as the number of divers you talk to, both old and new.

So I guess the question left to ask here is do you think that by exerting yourself you are increasing the pressure gradiant? Or are all these supposed experts wrong. Oh Duke Universtiy did a study that makes this claimm too, when I find the artical again I will give you the link if you want.

I think there is a slight disconnect here. First, in general terms, N2 loading in tissues behaves like the gas laws describe. I am sure there are a few subtle biochemical changes associated with exertion that modify the uptake rates but that isn't the real reason why exertion is bad for DCS.

Exertion as per DCS risk is better explained in the bubble models. IE, for a given N2 loading, what is the size and numbers or bubbles produced. Exertion lead to more micro bubble nuclei and hence, the potential for more bubbles, even if the N2 loading is within tolerance for a tissue model.

Either way, exertion at depth is bad for LOTS of reasons.
What about saturation diving?

in_cavediver
05-10-2008, 20:05
Awww cmon! Don't give up on me so easy. I find this particular subject interesting. There are so many differing thoughts. I actually do not totally disagree with you. The Gas laws are absolute. Your body can only absorb N2 so fast UNLESS the pressure gradient changes. (partial pressure or Dalton's Law) So why does almost all dive related material mention heavy exertion as a factor nitrogen loading. Why is the so much anticdotal documentation of excertion causing what appears to be a DCS event AT depth? I mean this is a direct cut and paste from a reputable dive medicine facility! Doesn't that warrent some open debate/discussion. I mean this is the information going out to new divers, it can't be toatally unfounded right?

The information out there on this is about as clear as mud, and you get as many different answers as the number of divers you talk to, both old and new.

So I guess the question left to ask here is do you think that by exerting yourself you are increasing the pressure gradiant? Or are all these supposed experts wrong. Oh Duke Universtiy did a study that makes this claimm too, when I find the artical again I will give you the link if you want.

I think there is a slight disconnect here. First, in general terms, N2 loading in tissues behaves like the gas laws describe. I am sure there are a few subtle biochemical changes associated with exertion that modify the uptake rates but that isn't the real reason why exertion is bad for DCS.

Exertion as per DCS risk is better explained in the bubble models. IE, for a given N2 loading, what is the size and numbers or bubbles produced. Exertion lead to more micro bubble nuclei and hence, the potential for more bubbles, even if the N2 loading is within tolerance for a tissue model.

Either way, exertion at depth is bad for LOTS of reasons.
What about saturation diving?

The interesting thing about saturation diving is the compression periods and decompression periods. The question arises on the life span of the micro nuclei for bubble formation. Does exertion followed by 10 hours of rest at depth behave differently that exertion followed by immediate ascent? I don't know the answer but I am quite sure the saturation protocols account for this. The time frames we are talking about are quite long, days and weeks sometimes.

Simply put, the tables used bring divers who work at depth up safely and as quickly as is safe. They don't really care if exertion is problem as they have to do exertion at depth and then safely get decompressed.

Perhaps a commercial diver can chime in here with more information?

Penguino
05-10-2008, 23:13
I think nitrox should be removed from the original list, at least at recreational levels. Yes it is more planning, but it is easily avoided. I don't think they would let rec divers use it if it wasn't safe

Black-Gorrilla
05-11-2008, 01:44
im glad i found this thread (by mistake might i add) i like the discussion thats going on.

ChrisA
05-21-2008, 16:41
.... "Tech" divers are some of the very best divers no doubt but also the ones making calculations about what could have been done, when the truth is; diving is dangerous and "tech" diving is very dangerous....

Dangerous, yes but if you look at who accidents happen to the group most at risk are what we might call relativly inexperianced vacation divers. These are people doing dives that should be easy. They are typically in warm clear water and superviser by a DM. But their problem and root cause of the accidents are that they don't dive enough to keep their skill current. Typically they do something stupid like rushto the surface because their mask flooded or panic when he BC leaks and they are sinking even with a full tank of air.

We see the same thing with travel. Some people think airplanes are unsafe but if you look at the numbers, driving to work is far less safe. When I look at the numbers Dan publishes I see most deaths are really medical problems that just happened to occure while diving. If you ignore these non-accidenets thenext larest group is the one I pointed out above. After that it is all over the map with not trend unless you group everyone who dove a dive outside of their training