A GUE shop might indeed try to persuade you to use their standard EAN 32, but the few times I wanted air (some years ago, for 20-ft training dives) they accommodated me.
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A GUE shop might indeed try to persuade you to use their standard EAN 32, but the few times I wanted air (some years ago, for 20-ft training dives) they accommodated me.
I was responding to the statement: "I don't see the benefits of using 32% for a 50ft dive...". I was hoping to provide a realistic (more or less) example that shows a diver can be NDL-limited if breathing air on a 50 fsw recreational dive, but gas-limited if breathing EAN32 on a 50 fsw dive. I was hoping to provide a way for this person to think about this, himself.
1. My quick hand calculations show that someone with a .45 cu ft per min RMV can breathe for approx 90 min at 50 fsw when diving a single HP100.
2. My U.S. Navy Standard Air tables give NDL = 100 min for a 50 fsw (air) dive.
3. My quick hand calculations give EAN32 at 50 fsw has an END = 40 fsw, for which my Navy tables give NDL = 200 min.
Hmmm. I didn't actully do these calculations until just now. I see now that my example would have been better if I had specified a HP120 or a HP130 (instead of a HP100).
Make sense?
rx7diver
In just about every thread the OP gets a totally clear GUE answer at the latest by post 3 (in this case the 2nd post) and yet here we are on page 4 of yammering by mostly people trying to "debunk" that validity of things like different wings for different dives, long hoses, continuous harnesses, BM cave diving before SM caving diving, standard gases, pretty much every GUE SOP has someone chiming to critique it.
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Right, we will all use helium over 100 feet 
that's a good one.
So why would a GUE shop even have an option for providing EAN21?
Most shops that serve GUE divers (e.g. Eight Diving in Des Moines, WA) also serve divers with other training and background. Why wouldn't they provide Air fills?
I have no doubt that GUE certified divers have some valuable skills. My question is....... what are the GUE prescribed equipment rules for configuring where and how to manage and stow your speargun, fish stringer, cocking device and goodie bag when shooting Lingcod and gathering crab, lobsters and scallops?
So they don't have to "school" folks like the OP on this post for coming to their shop and simply asking for an air fill.
To answer the O: GUE does not use "Nitrox only." GUE divers use O2 and trimix, too.
Gas standardization is a good thing. Besides helping with complex dive planning, it makes it possible for serious tech shops to bank standard gasses. Properly blended and banked gasses are usually spot on for the ratios and are quicker to fill, at least in my experience. E.g., if I must get banked 15/55 it is just a fill vs "blend-and-wait" if I want to get some bastard gas or a non-banked mix.
Minding MOD PPN2 and PPO2 is also a good thing, and GUE has standards around that.
TL;DR - if you buy into GUE philosophy, it all makes sense. If you don't get GUE things, this thread is just another "cool-aid."
Gas standardization is a good thing. Besides helping with complex dive planning, it makes it possible for serious tech shops to bank standard gasses. Properly blended and banked gasses are usually spot on for the ratios and are quicker to fill, at least in my experience. E.g., if I must get banked 15/55 it is just a fill vs "blend-and-wait" if I want to get some bastard gas or a non-banked mix.
Minding MOD PPN2 and PPO2 is also a good thing, and GUE has standards around that.
TL;DR - if you buy into GUE philosophy, it all makes sense. If you don't get GUE things, this thread is just another "cool-aid."
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