DIR Answer Required

[lamont]

I think you need to rethrink that, Lamont. My tires are filled with nitrogen. It is supposed to be a far superior mix.

hehehe, fair enough =)

air is pretty useless then...

cheap and plentiful on the surface seems to be its only major benefits....

 

[Cacia]

I will bow out of this thread. But first, I want to say that there are legitimate reasons why a "non-DIR compliant" diver would ask DIR divers for an answer. My reasoning is that, since they are not computer dependent, they might me the best at the mental "system" for ongoing computations while diving an unknown multilevel profile. I aspire to learn to be better at this and hearing different divers method really is helpful. I did well in a physics class, but frankly, I struggle with deco math at depth. Sometimes, I slip into deco and I am not sure how it happened. (sometimes a bounce, or a bouy dive with my computer on)

Nothing diabolic or clandestine about my intentions. I accept your apology Bob.
I do not live in the "PM" world, it gets too complicated. PM's are useful but it's best to keep most issues "above board", in my way of operating. Sometimes people take me on in public and then wish I would respond "privately".

 

[darkpup]

Jason, what's the logic behind using air down to 60' but not down to 100'? I was under the impression that 32% Nitrox was recommended for all dives above 100' when available.

Is the logic for 32% rather than Air based solely on less Nitrogen?

Is it personal choice? Is it the Standards and Procedures set by GUE? Is it solely to standardize the Team?

If the whole argument from JJ is that less Nitrogen is better, then why not dive 30/30 from 0 to 100' as the standard gas? Is it because 30/30 is more expensive thus making the gas less practical for daily use? At what price index does 32% become too expensive, and Air becomes a viable solution?

Since Air meets the GUE Standards and Procedures for depths above 100', why is it never to be used? If you can use Air when Nitrox is unavailable, doesn't that make it a personal choice rather than a standard? Or do you skip the dives that day / week because it costs too much or the Nitrox compressor is broken?

At what point do you decide to dive Air on 30' to 60' reef dives? Are you still DIR if Air meets the Standards and Procedures set by GUE, but doesn't meet some GUE standard gas mix that seems to be random?

If GUE doesn't condone the use of Air for any reason, why do the GUE Cave Instructors in Mexico list Air as the Standard Gas for 0' to 30'? Isn't 32% better than Air for this range? Or does the benefit of 32% drop off at some point?

Why do groups like BAUE list 32% for 0' to 80', and 30/30 for 80' to 110'? I have mentioned that 30/30 is to be used for 80' to 120' (i.e. my RecTriox class in 2005), and some have mentioned Bob Sherwood is now teaching 30/30 to be used for 80' to 100' and 21/35 for 100' to 150'. (http://www.baue.org/procedures/standardmixes.html)

What are GUE's standard gasses, and how do they relate to the GUE Standards and Procedures document? (http://www.gue.com/Training/Standards/index.html)

Why is Air never to be used if it meets the requirements outlined in the GUE Standards and Procedures document? Why?

~ Jason

 

[MXGratefulDiver]

I accept your apology Bob.
I do not live in the "PM" world, it gets too complicated. PM's are useful but it's best to keep most issues "above board", in my way of operating. Sometimes people take me on in public and then wish I would respond "privately".

As you wish ... I have no desire to take you ... or anyone else ... "on". Participation in this board isn't a competition ... at least, not to my concern.

I take responsibility for my responses ... and none whatsoever for yours. I just figured a one-on-one conversation might help clear up some of the differences that seem to be getting in the way of our conversing with each other as reasonable people should.

... Bob (Grateful Diver)

 

[Charlie99]

Jason, what's the logic behind using air down to 60' but not down to 100'? I was under the impression that 32% Nitrox was recommended for all dives above 100' when available.

It's pretty much the same as why is nitrox acceptable at 80', but not at 120'. At some point you have to choose a cutoff, and GUE has chosen 100' END. Obviously, the END of 30/30 would be less than EAN32, even at 60' or 80', but at some point the added benefit is very little.

Nitrox has decompression benefits over air. At some point you choose a cutoff. Per Jason, some DIR-F and Rec Triox instructors have chosen 60' as the cutoff. Others have chosen 0'. I was very willing to believe an earlier post which initially indicated 33' as the cutoff, because nitrogen loading really does become not relevant in a 15' pool dive, or an reasonable length open water dive with max depth somewhere in the 20' to 30' range.

-----------------

On a related subject -- Does anyone know if Level 1 Recreational Divers are taught about nitrox, or does this only get taught as part of Level 2? The GUE standards mention learning about nitrox as a specific goal for level 2.

 

[cmalinowski]

It's pretty much the same as why is nitrox acceptable at 80', but not at 120'. At some point you have to choose a cutoff, and GUE has chosen 100' END. Obviously, the END of 30/30 would be less than EAN32, even at 60' or 80', but at some point the added benefit is very little.

Nitrox has decompression benefits over air. At some point you choose a cutoff. Per Jason, some DIR-F and Rec Triox instructors have chosen 60' as the cutoff. Others have chosen 0'. I was very willing to believe an earlier post which initially indicated 33' as the cutoff, because nitrogen loading really does become not relevant in a 15' pool dive, or an reasonable length open water dive with max depth somewhere in the 20' to 30' range.

-----------------

On a related subject -- Does anyone know if Level 1 Recreational Divers are taught about nitrox, or does this only get taught as part of Level 2? The GUE standards mention learning about nitrox as a specific goal for level 2.

I think that a lot of it also has to do with... hmmm... the "viscosity" of he various gases and our ability to respire (or whatever the verb form of respiration is) these gases. I don't have my dirf slides handy, but I remember the slide and thinking "wow, really?" The drop-off in respiration ability is quick and significant if I remember correctly.

The viscousness (another unsure-of and possibly made-up word) of the gas mixture makes breathing harder which has other unwanted side effects such as CO2 buildup.

Then we get into the toxicity of the various gases, especially the build-up of co2...

Chris

 

[darkpup]

For the record, it looks like I was wrong on the Air 0' to 60'. I went back over my RecTriox Exam, and found the following question.

4 pts 7. List the GUE standard mixes for the following depth ranges:
32% a. 0 – 80ft (27m);
30/30 b. 80 (24m) – 120ft (36m);
21/35 c. 120 (36m)`– 160ft (48m); and
Air d. Fill Tires.

~ Jason

 

[Vayu]

The viscousness (another unsure-of and possibly made-up word) of the gas mixture makes breathing harder which has other unwanted side effects such as CO2 buildup.

Oxygen is denser than nitrogen. Therefore, nitrox is denser than air. Helium is not very dense and therefore contributes to the ease of breathing at greater pressures. I don't think that the gas density differences between a 21% mix and a 32% mix will be noticeable within recreational ranges.

 

[cmalinowski]

Oxygen is denser than nitrogen. Therefore, nitrox is denser than air. Helium is not very dense and therefore contributes to the ease of breathing at greater pressures. I don't think that the gas density differences between a 21% mix and a 32% mix will be noticeable within recreational ranges.

Hmmm... I certainly can't argue with you. I don't have my slides for one, but I'm just not that bright, nor up on my gas viscocity I will have to go and read the notes I took on the slides and see if it makes more sense.

It may be that the difference was being outlined for the use of helium, with some benefit for nitrox over air, but not important enough to warrant a change based on that alone.

The fact that you can base any calculations on one gas and not have to worry about which gas is in the tank(s) and making a mistake on that is also convenient. There is something to be said for simplicity helping diminish error I guess. If it was all based on depth/ppo2, then we'd use the max EANx we could for the depth.

Chris
PS: I dove tire gas on Sunday. I admit it. OK? You happy? Now my DIR buddies are going to mock me... although, one knew it because I was diving with him and I tested in front of him. I'm so embarrased.

 

[Derek S]

PS: I dove tire gas on Sunday. I admit it. OK? You happy? Now my DIR buddies are going to mock me... although, one knew it because I was diving with him and I tested in front of him. I'm so embarrased.

Let me be the first to start.....

HA HA! You dove tire gas!!!

Looking forward to seeing you, Ed P and the rest of the group soon (still healing from my surgery)...

Derek