Request for opinions about standardizing on EAN80

[doctormike]

You need the 50%. You've got a gas that you can switch to at 70ft which really impacts minimum gas volumes when compared to 30 or 20ft.

I'd keep what you've got.

100% is the most efficient deco gas. Divers also have less bubbles post oxygen deco when compared to other gases (gf held constant). its useful on the surface for dcs. 80% involves 2 fill whips, oxygen involves 1, reducing chance of contamination. Less of a concern IMO with things like 50% as the o2 pressures are much lower. Lots of drawbacks for 80%.

OK, thanks! So then don't standardize, but continue to have two different bottles, and just chose between them based on the profile? Again, was just interested in using only one mix, but it's certainly possible to continue to bring both 50 and 100 on the boat with me. Not going to carry two bottles at this point.

---------- Post added September 6th, 2015 at 06:20 AM ----------

The only operational safety issue would be if you can't hold a 6m stop. EANx80 MOD is 10m. If you have buoyancy issues such that you would need the extra MOD safety factor because you can't hold a 6m stop without a 4m swing, you probably shouldn't be doing technical diving.

That being said, the amount of time difference in a deco obligation running EANx80 vs. O2 isn't much when diving in the realm where a single AL40 is enough gas for your deco. If you're using 2 AL40's worth of EANx80, you should probably be reevaluating your dive plans and your deco obligations.

Just as an example, a 45m deep, 30min bottom time using air as backgas, using EANx80 gets you out in 76 minutes running VPM +3. Using O2 gets you out in 80 minutes for same depth and bottom time. It actually takes longer with O2 because you can't make the switch until 6m so you're doing the rest of your stops through 9m on air. Of course 4 minutes is nothing.

Now, add 50% into the mix with the O2 and you're on deco gas substantially sooner (in this case 15 minutes, this can be substantial in cold water). Keep the 50%, keep the O2. Forget the 80%, not worth the hassle.

OK, thanks, but I wasn't interested in carrying both bottles - the question was wether to standardize on one mix if I was only going to be carrying one bottle on the dive. A typical two tank dive trip for me in my area would involve two deco dives, each of which planned with only one mix.

I'm OK holding the last stop, usually finish at 15 feet on the Carolina rig.

 

[karstdvr]

OK, thanks! So then don't standardize, but continue to have two different bottles, and just chose between them based on the profile? Again, was just interested in using only one mix, but it's certainly possible to continue to bring both 50 and 100 on the boat with me. Not going to carry two bottles at this point.

---------- Post added September 6th, 2015 at 06:20 AM ----------
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The wash out ratios between O2 and 80/20 are similar, and perhaps similar enough that you might be able to get by with one gas mix. Where my preference is to use 50/50 and 02 in two tanks, the key to me is that I know I have enough gas for deco, as well as a reserve, this is something you might not get in 1 tank. There are enough deco software programs out there that will allow you do to planning to see what the deco and gas obligation is based of a particular dive,and always build in a reserve.

 

[Wookie]

I prefer to make 1 mix, and have 2 standard gasses on tech trips. This is based on logistics of running a tech liveaboard, and having to store blended gas, and having limited space and time to do so, so the blend I prefer is 50%, and I like to provide 100% just for ease of storage. Now, in the US, I'm usually the only liveaboard providing banked trimix, banked nitrox, and banked deco gas and replenishing it on a per dive basis, and there are a lot of reasons inthe ocean to use 80 instead of 100, namely, the boat you are attached to rucks, and may rock a lot, so you don't really want to be at 20 (24, 16, 24, 16) feet on 100% even more than you want to be at 10 feet (6, 14, 6, 14). OTOH, i don't want to be out there anyway if the boat is moving that much, and you don't want to climb the ladder in that crap with a load of 40's slung. So anyway, I provide 50% and 100% as a matter of logistics rather than being the "correct gas". Besides, I need to provide 100% to the rebreather divers. They get fussy about that....

 

[karstdvr]

100% is the most efficient deco gas. Divers also have less bubbles post oxygen deco when compared to other gases (gf held constant). its useful on the surface for dcs. 80% involves 2 fill whips, oxygen involves 1, reducing chance of contamination. Less of a concern IMO with things like 50% as the o2 pressures are much lower. Lots of drawbacks for 80%.

Need some help here. Where I am not an 80/20 fan, seems like 80/20 would have less of a contamination issue than 50/50. Put the O2 in which is well filtered for moisture and contaminants,but you'd put more compressed air in with 50/50 than 80/20,which the compressed air is a greater source of contamination.

 

[doctormike]

The wash out ratios between O2 and 80/20 are similar, and perhaps similar enough that you might be able to get by with one gas mix. Where my preference is to use 50/50 and 02 in two tanks, the key to me is that I know I have enough gas for deco, as well as a reserve, this is something you might not get in 1 tank. There are enough deco software programs out there that will allow you do to planning to see what the deco and gas obligation is based of a particular dive,and always build in a reserve.

Thanks for the reply!

I have no problem planning gas volumes for the dives, the issue isn't having enough gas. If that was the question, I would just sling an AL80.

I don't want to carry two tanks on a dive because (1) the profiles that I am diving now don't require that, and (2) I carry a large DSLR with dual strobes, focus lights, etc.. and I would rather only carry one bottle on a dive.

---------- Post added September 6th, 2015 at 07:51 AM ----------

I prefer to make 1 mix, and have 2 standard gasses on tech trips. This is based on logistics of running a tech liveaboard, and having to store blended gas, and having limited space and time to do so, so the blend I prefer is 50%, and I like to provide 100% just for ease of storage. Now, in the US, I'm usually the only liveaboard providing banked trimix, banked nitrox, and banked deco gas and replenishing it on a per dive basis, and there are a lot of reasons inthe ocean to use 80 instead of 100, namely, the boat you are attached to rucks, and may rock a lot, so you don't really want to be at 20 (24, 16, 24, 16) feet on 100% even more than you want to be at 10 feet (6, 14, 6, 14). OTOH, i don't want to be out there anyway if the boat is moving that much, and you don't want to climb the ladder in that crap with a load of 40's slung. So anyway, I provide 50% and 100% as a matter of logistics rather than being the "correct gas". Besides, I need to provide 100% to the rebreather divers. They get fussy about that....

OK, Frank.. now THAT'S a good reason stick with 50 and 100, since I plan on diving on the Spree as much as I can in the future!

 

[Wookie]

Need some help here. Where I am not an 80/20 fan, seems like 80/20 would have less of a contamination issue than 50/50. Put the O2 in which is well filtered for moisture and contaminants,but you'd put more compressed air in with 50/50 than 80/20,which the compressed air is a greater source of contamination.

And now we need to standardize nomenclature. To me, nitrox is expressed in terms of percentages, and trimix is expressed in terms of 2 percentages, shortened to 2 numbers with a slash, and nitrogen is never discussed. So, 80/20 would be 80% Oxygen, 20% helium, which would make a fine, if expensive deco gas, and 80/20 nitrox would only be called 80%.

 

[Nasser]

The benefits of O2 over EAN 80 are really not that much, at least for "moderate" dives in terms of efficiency, deco time, etc..

In some places like here in Aqaba and other parts of the Red Sea that offer Nitrox as a deco gas, it's been my experience that 80% is by and large the standard on offer for open circuit. Sure you could ask for 02 if you really want it, but it's more like walking into a tech operator and grabbing what's on the shelf and off you go... and that's usually EAN 40, 50, 60, 80.

If you already have O2 available to you then frankly I see no reason to switch to 80%. Likewise for me since 80% is more common and readily available here I see no reason to insist on 02.... the benefits are so marginal that it's not really a consideration.

 

[karstdvr]

And now we need to standardize nomenclature. To me, nitrox is expressed in terms of percentages, and trimix is expressed in terms of 2 percentages, shortened to 2 numbers with a slash, and nitrogen is never discussed. So, 80/20 would be 80% Oxygen, 20% helium, which would make a fine, if expensive deco gas, and 80/20 nitrox would only be called 80%.

I guess to be more correct we can't call them trimix,but heliox,since there is no nitrogen component. The use of 80/ 20 and 50/50 to indicate nitrox based deco mixes has been around for 20+ years,but you are correct that is incorrect nomenclature, and needs to be identified correctly.

 

[kwinter]

1) Leaving aside the deco issues, are there safety reasons for standardizing on EAN80 when compared to 100% O2?

2) Do any of you feel that there is a significant advantage of EAN80 in terms of oxygen injury (CNS clock, vascular perfusion, pulmonary injury)? Air breaks? Anything else...?

Yes. As you read through all those threads you will see I am a strong proponent of 80% over 100%. The small advantage of 100% over 80% in terms of reduced deco is much smaller than the increased risk of O2 exposure.

First, the benefits touted for the oxygen window went out that window a while ago. The theory behind that has pretty much been forgotten.

It sounds like you are minimizing any and all risk of O2 exposure, whether CNS clock or OTUs. I couldn't disagree more.

If you can get 100% regularly, there's NO REASON to get EAN80.

Disagree

There is the issue of contamination. If you just get oxygen, it is less likely to be contaminated, versus air from a compressor which might not be so clean one out of 50 times?

Ridiculous example. If the compressor is contaminated, he's gonna die from his bottom gas, not the 25% air in the nitrox tank.

You need the 50%. You've got a gas that you can switch to at 70ft which really impacts minimum gas volumes when compared to 30 or 20ft.

I'd keep what you've got.

I agree. (Scary, isn't it?) There is a reason to have both 50% and a higher deco mix on a dive. But I realize the OP is wanting to standardize on only one gas.

100% is the most efficient deco gas. Divers also have less bubbles post oxygen deco when compared to other gases (gf held constant). its useful on the surface for dcs. 80% involves 2 fill whips, oxygen involves 1, reducing chance of contamination. Less of a concern IMO with things like 50% as the o2 pressures are much lower. Lots of drawbacks for 80%.

Ok, now we're back to disagreeing. Just keep spouting that GI3 stuff, AJ

Now, add 50% into the mix with the O2 and you're on deco gas substantially sooner (in this case 15 minutes, this can be substantial in cold water). Keep the 50%, keep the O2. Forget the 80%, not worth the hassle.

That is worthy of consideration if you want to only carry one deco gas. But it might mean carrying a larger deco cylinder.

OK, thanks! So then don't standardize, but continue to have two different bottles, and just chose between them based on the profile? Again, was just interested in using only one mix, but it's certainly possible to continue to bring both 50 and 100 on the boat with me. Not going to carry two bottles at this point.

Two bottles is better, but if you want to limit to one bottle it certainly should NOT be 100%. If you can do the dives with a single cylinder of 50%, that would be fine.

And now we need to standardize nomenclature. To me, nitrox is expressed in terms of percentages, and trimix is expressed in terms of 2 percentages, shortened to 2 numbers with a slash, and nitrogen is never discussed. So, 80/20 would be 80% Oxygen, 20% helium, which would make a fine, if expensive deco gas, and 80/20 nitrox would only be called 80%.

Yeah, Kelly confused me with his numbers too.

 

[Nasser]

First, the benefits touted for the oxygen window went out that window a while ago. The theory behind that has pretty much been forgotten.

I'm not sure what you mean... could you explain this a little more?

Thanks