That would typically be more difficult to blend than 21/35 or 18/45 - at least if you were using 32% (another "standard" gas) as the top off gas.I've heard of 18/35 as well as wondered if that is because of ease of blending.
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That would typically be more difficult to blend than 21/35 or 18/45 - at least if you were using 32% (another "standard" gas) as the top off gas.I've heard of 18/35 as well as wondered if that is because of ease of blending.
That would typically be more difficult to blend than 21/35 or 18/45 - at least if you were using 32% (another "standard" gas) as the top off gas.
I like to use the rule of thumb where I choose as my dil the standard gas I would use for OC to the next depth range below the one I plan to go to. For example, RB using 18/45 dil to depths where I would use 21/35 on OC. This puts your PO2 closer to 1.0 after a dil flush at your planned max depth. This also allows some margin for "accidentally" dropping below the planned max depth without actually exceeding the MOD of my dil. So I still use standard gasses, which are easier to find or blend, but lower the likelihood of hitting an excessive PPO2 when adding dil at max depth.Standard OC bottom gasses don't necessarily work for diluents because they are designed around a ppO2 of 1.4-ish at max planned depth (and not 1.0 or 1.1) and they are designed to be blended using Helium and Nitrox32 and gas density isn't as important.
For example, 18/45 is generally used for depths up to 200'/60m. The "problem" with using that "standard gas" for a diluent gas is that 18% O2 has a ppO2 of about 1.3 at 60m.
So first you mix a non-standard Nitrox (28%) in order to make it easier to mix a non-standard trimix (18/35)? Seems a bit complicated to me. Or are there really shops that bank unusual nitrox blends like EAN28?If a shop has EAN28 banked, then mixing 35% helium and 65% EAN28 will yield 18/35 (actually, FO2 = 18.2, FN2 = 46.8, and FHe = 0.35). Straightforward.
rx7diver
Or straight He + 32%, or any of the other (lower O2 / higher HE) standard trimixes + 32%21/35
18/45
15/55
12/65
10/70
With the exception of the obvious, these can all be made using preblended 10/70 and 32/00
Well, 21/0 is a good dil for dives up to 100' or so (like when you get your first RB and are putting hours on it at a "safe" depth) or even up to 130' if you're not yet trimix certified, since the RB (or yourself) is basically blending your EAN28 to EAN36 continuously on the fly to maintain your set point.This is maybe a GUE standard gas for suit gas and tires, but not for dil... ;-)
Oh come on, you should know better than thisWell, 21/0 is a good dil for dives…even up to 130' if you're not yet trimix certified,
Well, 21/0 is a good dil for dives up to 100' or so (like when you get your first RB and are putting hours on it at a "safe" depth) or even up to 130' if you're not yet trimix certified, since the RB (or yourself) is basically blending your EAN28 to EAN36 continuously on the fly to maintain your set point.
I don't understand why anyone would do air dil, just go straight to helitrox. It seems like an instructor telling you no is just trying to sell more classes. Maybe I am way off base on this one and always reserve the right to be wrong, I'd love to hear justification for that intermediate class.
If air dil is good enough for your planned depth, just dive OC. For TDI at least, why even go CCR if you haven't exhausted all of the dive sites you are interested in that can be done on OC? Maybe I'm the odd man out here but I went CCR because it was time for helium. There were dive sites I could see and I knew I couldn't / shouldn't go to them without Tx.
Yeah, that's basically what I said.I don't understand why anyone would do air dil, just go straight to helitrox. It seems like an instructor telling you no is just trying to sell more classes. Maybe I am way off base on this one and always reserve the right to be wrong, I'd love to hear justification for that intermediate class.
I, too, initially went with the RB to break past the I can't carry / afford enough trimix to do the deep dive I want to do (especially with a buddy already on a RB). However, I did find that once I had it, it also solved the problem of I can't carry enough gas to do the shallowish (air / nitrox range) cave, wreck, or long OW dive I want to do.If air dil is good enough for your planned depth, just dive OC. For TDI at least, why even go CCR if you haven't exhausted all of the dive sites you are interested in that can be done on OC? Maybe I'm the odd man out here but I went CCR because it was time for helium. There were dive sites I could see and I knew I couldn't / shouldn't go to them without Tx.