When to use different EANx Mixes?

[vondo]

If you do not know the answer to this question then you need to do the course again with another instructor. Im sorry to be so harsh but this stuff is the most important to learn in the nitrox course. If you do not know what Dalton's diamond is then retake the course with another instructor and make your previous instructor refund your fees. If you do not know how to calculate your MOD, PO2 and OTU then diving nitrox is very dangerous!

I understand Nitrox perfectly well but had never heard of Dalton's diamond. Having looked it up, it's worthless if you understand the actual concept. It's kind of like the observation that engineers have three Ohm's laws: V=IR, R=V/I, and I = V/R.

And as other's have said, they OP is only halfway through his course, so how about refraining from telling him he got a junk course until after he finishes?

 

[ZenDiver.3D]

Thanks, we used the "pie" or tri-forcated circle in the ANDI class. It does make the calculations easier to derive.

Sorry ZenDiver.3D, but bashing an agency because they don't use the same term for a derivation tool is uncalled for. If I were to base my opinion of SDI on the Solo Diver manual for teh only SDI course I have taken, then I would say SDI is the worst, crackpot certification agency out there. But I am above that, and I know that there is a lot of other important information in the other SDI/TDI courses that are available.

Don't go there. I said," If not, I would never suggest PADI teach a nitrox course then. Or ANDI, if they didn't cover it. " And I mean exactly that. I have no idea exactly what they do or don't teach and did not profess to. I made a rather clear statement that was not bashing. If, in fact, the course and instructor does not teach how to calculate needed information and explain them, then I will say do not use that agency for that class. I didn't bash either one.
You, on the other hand, just did exactly what you accuse me of.

 

[vladimir]

Add me to the list of those who understand nitrox perfectly well and have never heard of Dalton's diamond.

 

[muddiver]

Don't go there. I said," If not, I would never suggest PADI teach a nitrox course then. Or ANDI, if they didn't cover it. " And I mean exactly that. I have no idea exactly what they do or don't teach and did not profess to. I made a rather clear statement that was not bashing. If, in fact, the course and instructor does not teach how to calculate needed information and explain them, then I will say do not use that agency for that class. I didn't bash either one.
You, on the other hand, just did exactly what you accuse me of.

Nope, I just made up an example.

I apologize for mis-interpeting your statement.

 

[halocline]

The "accepted (basic) recreational limit" has for all practical purposes shifted upwards to 100ft with 130ft being the limit for "deep certifications". I don't see 32% falling off the standard/pre-mix horse anytime soon just to accomodate the relatively rare 110-130ft nitrox dive. The fact is that nitrox just isn't that useful for deep recreational (100-130ft) or shallow technical (130-150ft) diving so there's little market for e.g. 28% premix. And for the same reason there's little interest in 40% fills for 50ft dives.

I agree that 32% is probably going to stay as the standard pre-mix nitrox for recreational use. However, I have never heard 100 ft mentioned as a limit for recreational diving. Certainly the agencies might have recommended maximum depths for varying levels of certification, but in my experience the commonly bantered about limit for recreational diving, regardless of certification level, is 130 ft. I'm not suggesting that ALL recreational divers are qualified to dive to that depth, or that anything deeper is technical diving only.

Personally, I'm comfortable diving 32% slightly deeper than the 1.4 MOD of 111 ft, although I wouldn't spend an entire dive at that depth. I think the usefulness of nitrox at this depth is dependent on the dive schedule; if you're planning on five dives in a given day, the first of which is between 100-130 ft, it's pretty useful.

 

[Quero]

My main question was geared towards choosing the best mix at specific depths. Why can't I ask this question on SB when many people here are instructors themselves. Of course, my instructor should tell me, but so what if I post the question here as well? There are a lot of people on SB that pose similar questions, even more basic than mine. I am just interested to hear about other opinions - isn't that the purpose of a forum?

Don't worry about it grammaticus. I recently saw SB referred to as a "piranha tank" when it comes to the aggressive posture adopted by some members as they post responses to questions posed. New members like yourself are often shocked at the apparent vitriol, but you should know that it's not personal. These aggressive posters are quick to criticise and slow to praise with everybody in their online personnas (sort of like Simon Cowell is on television). They are probably perfectly pleasant people in face to face situations.

 

[ZenDiver.3D]

I am almost finished with the PADI nitrox course, but I am wondering if people on this forum can give me some information about when to use different nitrox mixes. I don't think that the PADI course explains this issue very well.

Thanx.

Well I have a rough idea from the book. PADI mentions that you should not exceed 100% O2 exposure per day, and that you should not exceed 1.4 or 1.6 max per dive. Using different mixes on each dive is not covered on the theory behind the calculations. However, you do have to do some calculations using different mixes. PADI suggests in their book that you don't have to even do the dives, but it is recommended that you do. After reading the book, this seems to be dangerous if you don't do the dives and understand how to do the calculations thoroughly.

It seems to me that the deeper you go the less EANx you want to use. This could be wrong, but it begs the question whether EANx would be better for deep dives, say theoretically 130ft? I am not sure if that's completely true. I did a mock plan for the following dives:

1. 100ft EANx32 20min
2. 60ft EANx36 50min
3. 50ft EANx40 80min

According to my calculations, this would be alright with S.I.s at about 1hr each. I don't think that I would ever do 3 dives with 3 different mixes like this, but they are just hypothetical. I would be interested in what you would have to say.

Best wishes.

Not explained. They just said that I should just read the book and if I have questions the instructor will discuss them with me. I should just take the exam then off I go. Good thing I told them that I want to do the dives!!!

I understand Nitrox perfectly well but had never heard of Dalton's diamond. Having looked it up, it's worthless if you understand the actual concept. It's kind of like the observation that engineers have three Ohm's laws: V=IR, R=V/I, and I = V/R.

And as other's have said, they OP is only halfway through his course, so how about refraining from telling him he got a junk course until after he finishes?

Dalton's Diamond is just a term that helps people remember the calculations and equations. As long as you were taught how to find mod, ppo, and best mix, you have covered it.

And I am going by the quoted OP above's statements. OP states quite clearly that they are almost through with the course, have relied pretty much only on the book, and the instructor is only answering questions after reading without actual instruction. If this is true, then there are serious problems here, most of which may reside squarely on the instructor's shoulders. But if the standards allow this, then the agency is also at fault and it is a junk course either way, if not both.

 

[vondo]

I'm not a fan of "online-only" courses really, but it's a little hard to tell if that's what the OP is getting. If he's getting a "read the material ask questions if needed and then come in for a couple of hours and we'll talk" kind of course, that may work better for him than a pure lecture course.

But it actually seems to me that the OP does actually understand the theory (especially from his later posts) and is anxious to ask a few questions and came here instead of asking his instructor. I don't think there's anything wrong with that. But too many people here are too anxious to tell people their training sucks and they should "demand their money back" that we're not as welcoming as we could be.

I think a few other people answered the apparent question (what do you use in practice) fairly well, but I'll take stab too. Basically dive what mix you can easily get that still fits in the MOD of the dive. For a lot of us, this now means banked nitrox. So in my case, I dive 32% from 60 ft down to 110 ft or so. Above 60, I just use air. Deeper than 110' I'll get my Nitrox topped off with air targeting 28-30% or so depending on the depth. In NC, which is deep (110-130') wreck diving they just bank 28%.

Nitrox is a tool. How you use it is up to you (as long as you remain safe). For me it's not worth the added money and trouble to get 36% or bother with absolute best mixes or use it on shallow dives. And as you get much over 100 ft, it's benefits decrease because you have to start diluting the mix.

 

[ZenDiver.3D]

Nope, I just made up an example.

I apologize for mis-interpeting your statement.

Thanks. Then I'm sorry for biting back. I really try not to bash agencies. It is usually a problem with course structure by instructor or those crappy instructors who give the rest of us bad names. And no, I am not bashing instructors. I am an instructor and hate when people don't get the teaching they should

 

[rjack321]

I agree that 32% is probably going to stay as the standard pre-mix nitrox for recreational use. However, I have never heard 100 ft mentioned as a limit for recreational diving. Certainly the agencies might have recommended maximum depths for varying levels of certification, but in my experience the commonly bantered about limit for recreational diving, regardless of certification level, is 130 ft. I'm not suggesting that ALL recreational divers are qualified to dive to that depth, or that anything deeper is technical diving only.

100ft is (for instance) a SSI and PADI recommended maximum without additional training and/or experience. 130ft is gradually becoming more like an "absolute recreational max" at least here in the USA with the RTSC partner agencies. Each agency has slightly different language around the >100ft but <130ft issue but the general trend is in many ways like ppO2s and "contingency" ppO2s. 100ft in increasingly discussed as a recreational limit for an AOW diver with >100ft but less than 130ft being something "special". Its mostly a change in tone/discussion to encourage newer divers to back off a bit and treat this depth zone with increasing caution.
<60ft = BOW recreational limit
>60ft but <100ft = AOW recreataional limit
>100ft but <130ft = "deep diver" specialty etc.

While the cynical probably think its just a money ploy to sell specialty courses, the reality is that most divers aren't prepared to go from 50ft to 120ft diving as fast as they think they can progress. So putting up an intermediate depth/experience/training "limit" is in the industry's best interest. Nitrox actually tends to do this already. Since 32% has become a defacto "standard" most nitrox divers are now happy at 100ft or less and there's no losing face when you and your 20 lifetime dive buddy can't push to new personal depth records on every dive.