Best Mix VS Standard Gasses (split from a GUE fundies course report)

[Ayisha]

...There is NO reason that Best Mix divers should ever be sitting on the boat while the Standard Gas divers are diving. The posts that suggest otherwise are simply false.

In my opinion.

You missed the point. In my example, if you're referring to mine, the diver did not choose a best mix wisely. I emphasized that we would know what the contingency options were in case of a blow-out. Knowing that the captain had arranged a 100 foot sheltered dive in Lake Ontario in case we couldn't get to the 80 foot dive in Lake Erie, he should have chosen a gas that was suitable for both depths, but he didn't. Everyone else did. No, he didn't sit on the boat. He turned around on route.

The main purpose of that post was in response to what I quoted in it, which was essentially the assertion that charters don't change their planned dive sites or depths and that it was irresponsible on the dive op's part. I have seen it many times, not from recreational to technical depths, but within recreational depths.

 

[_Ralph]

Just for clarification, i’ve been taught both methods from several organizations.

If I was to follow what IANTD wants me to do on my CCR regarding DIL, bailout and deco gases, i’d spend a few days calculating out and dumping gas every dive (in its purest sense).

Since my CCR uses larger DIL tanks for bailout, their methodology doesn’t fit.


I’ve sat in a few excellent TDI AN/DP courses which cover best mix very well, would leave me with about a minute to calculate everything I needed for a dive.

Standard gases, everything else is taught. How to come up with best mix, all the calculations, but based on a set of criteria, a selection of gases to get you diving fast and easily is made available. There is considerable thought to how easily the gas is mixed, what the CNS calculations work out and how decompression works with the selected gases and ranges.


With best mix, you have to do that for yourself.

Some people prefer all that extra work to squeak out an extra minute or two of bottom time vs decompression, or there would rather not.

Neither is more right or wrong than each other, provided a diver follows the rules set out by their respected training agency.

_R

 

[stuartv]

You missed the point. In my example, if you're referring to mine, the diver did not choose a best mix wisely. I emphasized that we would know what the contingency options were in case of a blow-out. Knowing that the captain had arranged a 100 foot sheltered dive in Lake Ontario in case we couldn't get to the 80 foot dive in Lake Erie, he should have chosen a gas that was suitable for both depths, but he didn't. Everyone else did. No, he didn't sit on the boat. He turned around on route.

The main purpose of that post was in response to what I quoted in it, which was essentially the assertion that charters don't change their planned dive sites or depths and that it was irresponsible on the dive op's part. I have seen it many times, not from recreational to technical depths, but within recreational depths.

I don't think I was responding to you.

Anyone can make an error in judgment in their choice of gas. That is not a specific feature of Best Mix or Standard Gases, I don't think.

 

[ChuckP]

There ARE valid points against always sticking to Standard Gases. There is NO reason that Best Mix divers should ever be sitting on the boat while the Standard Gas divers are diving. The posts that suggest otherwise are simply false.

Truth!

One would be much farther advanced in training if they were taught implications of using best mixes over multiple dives per day at multiple depths or diving what's commonly available in any particular location and the implications.

32 is a great rec gas choice, for a first dive - if your 2nd, 3rd etc dives get shallower, why not breathe richer mixes?

Telling a guy he has to spend $120 on gas for a double dip on the Lady Luck? Really?

The push back is the black and white, this hobby we have is incredibly varied in recreational mode and when you step up to tech, it becomes even more varied......

Dive what fits you. Dive what makes you feel comfortable. Dive what is safe.

 

[_Ralph]

If we're diving together, why would you plan for the possibility of 150' while I only allowed for 130 in my plan? Personally, I would never do that. If we're diving together, I would use the same gas as you. In that scenario, I might request EAN25, but if you say you really want 21/35, then I'd dive that, too. I'm easy.

And, during our planning if we decide that there is some chance we might want to go to 150', then sure, I'd pick a gas for that. But, if we know that the bottom is 125' at the deepest site on our list of "even possibles", then I would vote for something like EAN30. If we (keyword: we) plan for a max of 130 and we get out and find there's a spot that we'd like to check out that's 150, well, too bad for today! Plan for it and come back another time.

If we're going out on a commercial charter boat, I'm going to ask ahead of time "what is the max depth you'll take us to?" I'll choose my gas accordingly (most likely being to use whatever they bank). If they take us out and end up taking us somewhere deeper than what they told me ahead of time and I can't dive, then I'm going to have words with that charter operator (and a refund).

The downside to 30/30 for a recreational reef dive at 80' is simply cost. I would feel like it was a good chunk of money spent for no practical benefit. But, I was stipulating common, ordinary rec charter boat dives. I interpret those as "easy dives". If you want to change the parameters to include work and task-loading, then my choice of gas might change. (though I really cannot see myself ever using He for an OC dive to less than 100'. If it's that shallow and that much work that I would think I needed helium, I probably don't want to do that dive anyway.)

If we were doing a dive together, we’d have The same gas, same bailout (if in CCR) same deco, same plan.

The question was you were diving best mix, and I was diving a mix found on a standard table.

In the example I laid out, i’d get to see the mermaid, and you’d be out of luck. You said there wouldn’t be a situation where a standard gas diver would be diving and the best mix diver would be sitting on a boat...


Thanks for the clarification on your reasons on why not to use helium shallow. Cost is a big factor (getting worse by the fill). Figuring a typical worst case US helium fill. $2 cuft in HP100’s is roughly $120 in helium, it’s not outrageous. But certainly is much more than a nitrox fill.

Certainly a best mix diver is very cost conscious.... as well, does one really need that much helium in their tanks that some standard gas tables suggest?

_R

 

[johnkendall]

In NC, lots of people want to go to the U-352. That dive is about 110'. It would not be unheard of at all for the boat to aim to go there, find out that conditions are bad there and go to, for example, the Atlas, which is 125 to the very bottom.

They can do that because everybody goes out prepared for the deepest option that is on the menu - and the Atlas is probably the deepest option on the rec boat charter menu. So, you may not have been anywhere with a fallback that is deeper, but that doesn't mean it doesn't happen.

Also, if you assume the fallback sites will always be shallower, then Best Mix will always be better - except in the case where the Best Mix works out to be the same as the Standard Gas for the planned site - in which case they are, well, the same. It was another GUE diver who originally asserted that Best Mix would potentially leave you sitting on the boat while the SG dives were diving at a (deeper) alternate site.

Also, I had no problem with your answers in PM. I just thought our discussion was done. I wasn't going to change your mind. You were not convincing me that what you said about Standard Gases is valid. The point in continuing the conversation here in a public forum was to air both sides fully, for the benefit of anyone who may come along and read this later.

As far as I can tell, for NC diving, EAN30 (a non-Standard Gas) is better, easier, and less expensive than using the prescribed GUE gas.

As far as I can tell, if I were going (on a recreational charter boat) out of Key Largo, the target site might be 90 feet (a Molasses Reef drift), with an alternate of 40 feet (a non-drift dive at a shallower spot on Molasses). EAN36 is a better choice there than the GUE Standard Gas (EAN32).

It seems to me that, for recreational sport diving, the examples of when a Best Mix approach yields better results for the diver might significantly outnumber the examples where they are equal. And there is never a time when limiting to a Standard Gas is actually better - because if it's better, the Best Mix diver can use it, too.

As for not being sure what I want you to answer, well, I don't know how many more different ways I can say "if you strictly adhere to GUE training, what gas would you bring on the boat on a NC chart boat (parameters previously given)?"

I think it is settled that you would bring TX30/30 or EAN32. I don't think I'm asking anything else for you to answer...? Unless you can explain how either of those would be better than bringing EAN30 (given the previously described, real, actually-how-it-is, parameters).

The disconnect is that you consider 30% suitable for 120ft, and I don't.
You give an example above with a seabed depth of 120ft, but what is the likely average depth for that dive? Can you do a decent dive on that site at 100ft?
If the boat tells me we're doing something with a max depth of 120, then I turn up with an appropriate gas for 120.
You are arguing against helium use between 100 and 120, and that is where the issue with our point of view differences arises from. This is not a standard gas thing, it's a Narcosis/gas density thing.

As I said before, if all that the shops pump is 30% then I'll dive 30%, but I'm not diving it below 100ft.

 

[barth]

In NC, if I were diving OC, I would do what everyone else does that goes there - take 2 tanks full of EAN30. And not lay on the bottom. And they don't take rec charters to anywhere with a bottom deeper than 125', so no anchor there at 135.

I asked specifically about going to do a NC dive. A GUE diver with no more than Fundies training, who is adhering to their training. I'm not getting dragged into what-ifs of other places. I only threw out a different location to illustrate that NC is not unique in the variability of what you have to plan for.

What I seem to have gathered so far is that this hypothetical GUE Fundies grad who wanted to dive NC (but adhere to his training) would:

- take their own tanks filled with TX30/30 - and possibly use them on 2 x 70 - 80 foot dives.

or

- take their own tanks filled with EAN32 and not dive deeper than 100'. If they end up on a site with nothing but blue water at 100', then they'd stay out, or jump in, see what's up, and get out. Fortunately, there aren't that many sites that are that deep and have that little relief.

If their only option for tanks was to rent what the dive shop there offers, they would just not dive - because the choices are Air or EAN30.

Have I captured all the options and accurately? Again, I'm asking what the official GUE training standards would say.

As @TrimixToo noted, Standard Gases are usually only thought of in the context of tech diving. But, my understanding is that GUE standards mandate use of Standard Gases on ALL dives - even purely recreational sport dives. So, how does that work out for recreational sport divers? Based on the number of divers I see diving the NC wrecks, going deeper than 100' and seemingly just fine with no helium - not to mention all the people I see who dive shallower than 100' using Air (instead of EAN32), it SEEMS to me like GUE Standard Gases are pretty limiting - not making "it easier" like the GUE people keep telling me. At least, for sport divers anyway.

At the Northsea I have done dives with a depth of 120-130 feet /36-39 meter with different gasses.

Ean30 (+ oxygen), max depth 35 meter, average depth 31 meter.
25/25 + oxygen
21/35 + ean50

But I would never do a single tank dive deeper then 100 feet / 30 meter. I would use doubles and deco gas since i’m tech certified.

The costs for the boat are 100 euro. Sometimes to boat leaves the harbor at 4:30 because of the tide. Because of that I also want to sleep in a hotel, cost 50 euro. Total cost for transport to the harbor by car (2x200km) 60 euro (can split in some cases between 2 divers).

If I ‘m paying 210 euro for a one day divetrip without gas and have to wait 5 hours for the next tide I will bring 2 sets of doubles and decogas.I will do 2 deco dives to spent as much time as possible underwater or I won’t book.

Almost nobody is doing single tank diving at Northsea even if the depth is 70 feet. Gue/non gue, everybody brings a rebreather or doubles.If there are divers diving single tank they just do 1 Northsea trip a year. Because everybody want to have long bottomtimes.

But even at other places then here I won’t dive with a single tank (and 30/30) deeper then 30 m / 100 feet. I don’t know gue divers or a gue course where they dive deeper then 30m / 100 feet with a single tank.

 

[rjack321]

The disconnect is that you consider 30% suitable for 120ft, and I don't.
You give an example above with a seabed depth of 120ft, but what is the likely average depth for that dive? Can you do a decent dive on that site at 100ft?
If the boat tells me we're doing something with a max depth of 120, then I turn up with an appropriate gas for 120.
You are arguing against helium use between 100 and 120, and that is where the issue with our point of view differences arises from. This is not a standard gas thing, it's a Narcosis/gas density thing.

As I said before, if all that the shops pump is 30% then I'll dive 30%, but I'm not diving it below 100ft.

you can stop arguing with him lol

There's very little helium in North Carolina
The wrecks are far offshore and get blown out regularly
But they are also very consistent depth, 120ft and its flat sand for miles around. You can't do a decent dive at 100ft. You also aren't going to magically get taken to a deeper site either.
Visibility is usually quite good
Currents are high
Not that cold (in the grand scheme of things)
Net: the "standard" mix there is 30% EAN

Trying to convince NC aficionados that anything else has value is pointless. This argument has been going on for 10+yrs

 

[johnkendall]

you can stop arguing with him lol

I know, today is a travel day, so I'm not busy actually diving.
Don't worry, normal service will resume shortly.

 

[stuartv]

Trying to convince NC aficionados that anything else has value is pointless. This argument has been going on for 10+yrs

The point is not at all that nothing else has value. The point is that best results come when tailored to the specific task. Trying to apply a one-size-fits-all chart of depths and gases to every single place you go can obviously work - well, except for when you can't dive because your table requires a gas that isn't available. But, thinking it through - instead of adopting the philosophy of "I have this chart, so now I don't have to think about that" - CAN work better.

@johnkendall dismissed my NC scenario with "I wouldn't do it without helium, so this conversation is pointless" but I guess didn't notice the other scenario I posited - heading out for a 90' dive off Key Largo and diverting to a 40-ish foot dive. Like I said in the preceding paragraph, EAN32 will work. But, EAN36 would work better....

Anyway, I do appreciate you all for not turning this is a bunch of name-calling and BS flaming. Being able to disagree and stay civil hasn't always been a normal characteristic of ... some Internet forums. So, thank you.