Why Recreational Triox ??

[Genesis]

Genesis,

I'm walking out the door to a meeting, so I'll try one time, but I doubt it will convince you of anything.

To convince, one must make their argument with facts. Drawing conclusions from a random set of facts without the pieces to tie together the assertions does not wash.

Where in the world do you get that we certify someone who we haven't even seen master anything??? Are you just making this stuff up as you go???

You certify someone to dive to 130' on Triox. You have admitted that the "DIR paradigm" does not permit such a dive to be made without gas redundancy (which I happen to agree with.) Yet you do not require that the student demonstrate that they can manage a redundant configuration (either a slung "stage", which I guess meets the DIR dogma even though some would argue its just a "pony", or doubles.)

How does this constitute "making this stuff up"?

I appreciate that you miss the C02 retention point, I apprecaite that you missed the gas density issue, I appreciate that you lack the understanding to weigh the cause and effect of the issue(s)

Here we start with the personal insults; does this constitute "trolling"? (only half rhetorically)

You have done nothing other than assert (without evidence) that CO2 retention at recreational depths on Nitrox is an issue, you have failed to link gas density at these depths to CO2 retention by anything other than "Mike says so - trust me" and you then claim that I "lack the understanding" to weigh a cause and effect that you have failed to demonstrate!

That you can show that when diving on "deep air" such an effect manifests and is clinically significant does not prove that this is also true at shallower depths. Are you arguing for diving Triox at 30'? 60'?

I also apprecaite the fact that you want to make a big deal out of the fact that GUE allows a class to 120' in a single tank. [ BTW, every other agency in the world allows this, and some even allow single tank(s) in their trimix class], but the point being other then you, John Walker and Jim Hoffman no one else shares your point.

Mike Ferrera seems to. People who have abandoned the idea of a CESA from depth seem to, generally-speaking, I suspect.

I happen to disagree with the OTHER agencies on this point too. SSI seems to think that for a "deep" dive hanging a bottle on the anchor line is an "ok" safety procedure, ignoring the fact that if it isn't with you all you've done is add even more trouble; of course equipment failures (or attention failures!) usually happen at the worst possible time, not when you're just hanging there on a safety stop.

Your chosen solution to a dive in the 120' range is to worry about CESA's. Our chosen solution is more pre-emptive. Let's solve the problem before it happens. Let's dive in a unified team so if it does happen your buddy goes 5' to you, rather then 120' to the surface. Let's use the correct gas to reduce narcosis and C02 retention so we have no need for a CESA, let's teach proper gas management and Rock Bottom concepts so you aren't doing CESA's..

My chosen solution is to NOT get in a situation where I might have to perform a CESA. I do this by carrying enough gas to cover the contingency of an equipment failure for either myself or my buddy (if I have one with me.)

Let's look at this "correct gas management" stuff eh?

Let's take a diver at 99' for grins and giggles, just to keep the math simple. Let's postulate that his normal RMV is 0.7cf/min. He's at 4ATA though, so he breathes 2.8cf/min there.

Now with two of those divers on one tank, they will consume 5.6cf/min. So what is the "rock bottom" computation? If we must make a free ascent, and the average depth during that ascent will be 33' (probably reasonable) then if we do 1 minute at 70', 1 at 50, 40, 30, 2 at 20 and then 3-4 from there to the surface. This diver pair will burn (average) 2.8cf/min, and will require 10 minutes to reach the surface, so that ascent, assuming they start instantly, requires 28cf.

But wait! That's not very realistic. Let's put some reality to this. We give you one minute to figure out what's going on and that you must bail before starting the ascent. That's 5.6cf gone. Also, the person who had the problem is at least a bit tense, 'cause this isn't a drill - this is the "real deal", so let's jack his RMV up by 50% - probably not enough, to be honest, but we'll be "nice". So now we take that 28cf and make it 42cf, plus the 5.6cf, or close to 50cf of gas required for a "rock bottom" reserve.

Heh wait a second. Thirds on an 80 is what - 53cf, right? Hmmmm.... funny how that works on those little tanks.... And oh, by the way, it gets a LOT worse at 130 with another ATA added in; now thirds doesn't even do it.

Note that I didn't accelerate the donor's gas consumption at all, but that's probably not realistic either.

So, we're back to reality here. You teach this class on single cylinders at depths of 100', yet single cylinders do not permit real "rock bottom" computations with honest, real values for the actual parameters necessary to be used on those dives unless they're just "touch" dives. In order to make those dives you have to make rediculously aggressive assumptions about people's RMVs, the effect of stress, and/or blow off at least some of the stops you would otherwise do, all of which are bad news IF any of them become necessary to actually do. And IF you find yourself in a bailout situation and have made those assumptions incorrectly, you now have two people OOA, on a gas that is unforgiving of CESAs, and the CESA is gonna be happening because there is nothing left to breathe between the two of them.

Rapid ascents are bad under all circumstances but in your way of diving your "last resort" option is more likely then if you adopt a DIR approach and put in place more solid foundations like gas management, like less dense gas, like unified team, like lower narcosis..

Again, arguing assertions as facts not in evidence, other than the unified team, which I'll grant you is a good ideal (but darn difficult to achieve in practice to the level propounded.)

I argue that singles (especially single AL80s) without redundancy below 100' is foolhardy. I believed otherwise when I first started doing these dives, but there was this little bird nagging me about reserves and assumptions, and when I started calculating things out I came to the conclusion that all I was doing was asking for TWO divers to end up OOA if there was a failure.

I've explained this too you now on several occassions, if it still isn't clear then I'm sorry I just no longer know how to break it down for you and let's just agree to disagree..

Later

You've continually "explained" this in the same way, but when I run the math it doesn't add. That's why I keep coming back to challenging you on this point - I believe its important.

IMHO gas redundancy is necessary below 100'. I used to think otherwise, and fortunately I thought enough about it BEFORE I had a failure and came to that conclusion. This resulted in a change to my gear configuration.

If you accept that this redundancy is necessary, then you must take the next step and say that to certify someone for diving to that depth, you first must see them dive to that depth in that configuration and actually manage it with reasonable aplomb.

 

[cornfed]

To convince, one must make their argument with facts.

LOL, that sounds an awefully lot like another guy named Karl... wink

 

[MaxBottomtime]

1) The class covers a range of depths. In the shallowest possible dives you're talking about a 70' dive using a 32% Nitrox. Does anyone believe that a set of doubles is required for that dive?? If not, then the rest of the discussion is quarreling over semantics and I'm not interested in getting into that game. Once you determine that a 70' dive using 32% Nitrox doesn't need doubles, then how can you write a standard that requires doubles??

2) No other agency in the entire world requires the use of doubles for dives in the 120' range..

Then why did you give me so much crap over taking my buddies to the Ace One on singles?
Seriously, if you want to continue stating that "the other guys teach it this way, so we do too" that will make GUE appear to be just like all the rest. And if you continue to emphasize the "70' dive using a 32% Nitrox in the Caymans", which you always do, then why not call it as it is, a Resort Triox course?

 

[Lane Zimmer]

Let's look at this "correct gas management" stuff eh?

Let's take a diver at 99' for grins and giggles, just to keep the math simple. Let's postulate that his normal RMV is 0.7cf/min. He's at 4ATA though, so he breathes 2.8cf/min there.

Now with two of those divers on one tank, they will consume 5.6cf/min. So what is the "rock bottom" computation? If we must make a free ascent, and the average depth during that ascent will be 33' (probably reasonable) then if we do 1 minute at 70', 1 at 50, 40, 30, 2 at 20 and then 3-4 from there to the surface. This diver pair will burn (average) 2.8cf/min, and will require 10 minutes to reach the surface, so that ascent, assuming they start instantly, requires 28cf.

But wait! That's not very realistic. Let's put some reality to this. We give you one minute to figure out what's going on and that you must bail before starting the ascent. That's 5.6cf gone. Also, the person who had the problem is at least a bit tense, 'cause this isn't a drill - this is the "real deal", so let's jack his RMV up by 50% - probably not enough, to be honest, but we'll be "nice". So now we take that 28cf and make it 42cf, plus the 5.6cf, or close to 50cf of gas required for a "rock bottom" reserve.

The math just does not add up for me.

If we're going to use a hypothetical situation, lets at least use the correct procedures. Given this situation, the team will not come close to the "no-deco" limits. They will burn an 80 long before they have deco obligations. The deco schedule for this dive should have been prepared beforehand in the pre-dive planning. The schedule that you give is too long for a dive of this nature. A minute at 50, 40, 30, 20 and 10 should be the schedule for this dive, maybe even a bit too conservative still. This cuts the deco time in half and, according to the example, cuts the air consumption in half. So now the team will only use 14 cu.ft. to surface safely. To stay true to the example, lets crank the OOG diver's SAC up 50%. Now the team uses 21 cu.ft. of gas to get up. Lets even throw in the 5.6 cu.ft. for a brain fart. Now they need 26.6 cu.ft of gas to get up. If you do the math, that's 1/3 of an 80.

To be truly realistic, even if we jack the OOG diver's SAC to 75%, it will not remain this way throughout the deco. A diver experienced enough to pass fundy's and take this class will calm down once he has gas. Also, a catastrophic loss of gas (burst disc, neck o-ring, etc.) is not an instantaneous loss of gas. The OOG diver will still have a minute or 2, at the least, left in his tank to breathe. It's enough time for the team to figure out what's going on and start to make an ascent. This puts the 5.6 cu.ft. back in the donors tank.

It is possible for this team to make a decent, safe dive to 100 ft on a single 80 and have enough gas for emergency. Anything longer or deeper would require larger tanks or doubles. This will also be determined before the team leaves the shop.

Common sense helps too. A 70ft reef dive is not the same as a 120ft wreck dive. The team should use good judgement and proper dive planning before they try to do a wreck at 120 on a single 80.

I also looked into the CO2 subject and found something interesting...


Undersea Biomed Res 1991 Jan;18(1):1-19 (ISSN: 0093-5387) Fothergill DM; Hedges D; Morrison JB
School of Kinesiology, Simon Fraser University, Burnaby B.C., Canada.

This study examined N2 and CO2 components of narcosis by comparing the effects of three levels of PETCO2 [low = 29 mmHg (SD = 4 mmHg), medium = 47 mmHg (SD = 1 mmHg), high = 57 mmHg (SD = 2 mmHg)] at 1 and 6 atm abs in 12 male volunteers. Cognitive and psychomotor performances were examined using a variety of tasks, including a modified Stroop test, an arithmetic test, number comparison, a figure copying test, and the Purdue pegboard test. Performance on all tasks demonstrated significant (P less than 0.05) decrements at 6 atm abs. High CO2 tensions significantly impaired cognitive and psychomotor performance at 1 atm abs and caused further decrements at 6 atm abs (P less than 0.05). However, no significant N2-CO2 interaction (P greater than 0.05) or global threshold for the onset of CO2 narcosis was indicated by the test scores. The pattern of intratest results were different for N2 and CO2. At high PETCO2, performance deficits were due to a slowing of performance rather than a disruption of the accuracy of processing. Nitrogen narcosis, conversely, produced significant impairment through both decreases in the speed and accuracy of processing on the majority of performance tests. It was concluded that within the PETCO2 ranges studied: a) PETCO2 and PIN2 are additive in their effects on impaired cognitive and psychomotor performance at depth; b) high PETCO2 and PIN2 induce distinctly different strategic responses on the speed accuracy trade-off function of the performance tests; c) decrements in cognitive and psychomotor performance under high PETCO2 do not conform to the predicted narcotic potency of CO2 according to the lipid solubility theory of narcosis.


Just my 2 cents...

Z

 

[lamont]

Hi Genesis. I'm not wanting to get into a big discussion on the issue of when and how much helium. But just wanted to point out that the helium supply issue has surfaced several times that I have seen and it would be irresponsible as divers to ignore that. Of course I also drive an SUV, but that doesn't mean that I shouldn't be conscious of how my actions impact the environment. A very long time ago, Ann Landers wrote an article about how she could not understand why people kept talking about the world's population since every time she is on an airplane, she sees all this open space available. But the issue of course was nonrenewable resources. Again, I'm not sure what to do with the thought, but didn't want people to just dismiss it and not be aware of how their actions affect the environment. Cars are being required to meet emission standards and address their impact on the environment. Perhaps there should be a “cost-benefit” analysis on how much and when to use helium. But the fact remains that I would always opt for and encourage too much helium over too little.

If He4 gets rare enough on the earth it will also get expensive enough that someone will figure out how to mine it out of the solar wind, from earth orbit or from the surface of the moon -- at which point it will rapidly get cheaper again. This will also have the benefit of providing a supply of He3 which is useful for deuterium-He3 fusion reactions which are 'neutron-clean' and provide almost as much energy as deuterium-tritium fusion.

Helium is the second most common element in the universe. We are unlikely to ever run out of it.

 

[DepartureDiver]

If He4 gets rare enough on the earth it will also get expensive enough that someone will figure out how to mine it out of the solar wind, from earth orbit or from the surface of the moon -- at which point it will rapidly get cheaper again. This will also have the benefit of providing a supply of He3 which is useful for deuterium-He3 fusion reactions which are 'neutron-clean' and provide almost as much energy as deuterium-tritium fusion.

So if it gets cheaper after getting expensive, is it cheap or expensive? Don't know much about He3 ... assuming you meant it is He with a change in the atomic mass from 4.00 to 3.00. Didn't know the atomic mass of an element changed.

 

[chrisch]

There are one or two good point here. The GUE course is half a Tech1 and that is debatable - we are however debating other things as usual.
Helium can be obtained from air distilation, but it is neon contaminted - this could be ok for scuba. (How refreshing to hear Americans that care about the environment!!).
Single tanks - a 15 liter tank with H valve gives redundancy and 3480 L of gas or 123 cubic feet. Enough for a 20 min BT at 40m (130fsw). Then you have some deco gas to go through as well.
Dive shops do like to make money and they do sell silly courses to do that (PADI equipment specialist anyone??)

Back to the point. The High Oxygen Trimix gas.

It does provided a staging post between true recreational scuba and the starting of deeper and more "technical" (if you must use that term) diving. Prior to using trimix I would never think about gas management - 50 bars left time to go up. Nor think about dive planning - computer says 3 minutes NDL left - time to find the shot line.
Therefore - from the viewpoint of a paying customer - I think the idea is valid. Sure helium has some drawbacks, but I'm training to use it more in future. Sure you might want to go to doubles - I don't have the cash right now for manifolds regs tanks and big wings.

I am doing the IANTD course as its deeper than the GUE one and I am not DIR or likely to be. We've had that debate elsewhere. However, I think the concept of "recreational trimix" is a good one and this is the GUE take on it. It is also great for diving in the 35-45 meter range which is a whole bunch of wrecks here in Europe.

Chris.

 

[Angiemac]

:sorry19z: It's me again. Asking "stupid" question.

And I can't help but wonder why the word "Receational" is being used ?

Where I come from any diving we do for fun and no pay is recreational - there are just subdivisions of it - technical, sport, etc. Perhaps they were originally BSAC trained and therefore still using basic terms.

Angie

 

[cornfed]

Didn't know the atomic mass of an element changed.

It's called an isotope.

 

[cornfed]

:sorry19z: It's me again. Asking "stupid" question.

And I can't help but wonder why the word "Receational" is being used ?

Where I come from any diving we do for fun and no pay is recreational - there are just subdivisions of it - technical, sport, etc. Perhaps they were originally BSAC trained and therefore still using basic terms.

Angie

In the US, "recreational" generally denotes a dives within the no-decompression/no-stop limits. I assume that was the reason it was employed here, but I'm just guessing.