When to use different EANx Mixes?

[disbelief]

Let's be clear here shall we, it's you telling people what to do, not me.

You are the one being prescriptive in saying O2 is narcotic, and pointing to Meyer-Overton as a definitive "rule".

I suggested that it's more complex than that, and that a cursory investigation will show a range of views on the issue. You seem to want to polarize the debate and cast me as the antagonist in an attempt to deflect attention from your definitiveness.

...
While Dr. Mitchell's a smart guy (and on this board as well albit rarely) that thread is over 4 years old and <still> this apparently measureable difference hasn't been measured. Which is saying something about the magnitude of the difference and its relevance to actual diving (not much).

I think you misunderstand the game. You choose to be definitive about the narcotic potential of O2, therefore the burden of proof falls to you.

 

[PfcAJ]

What, exactly, is the advantage to NOT considering o2 narcotic, other than nickel rocketry and false bravado?

Seems to me that there IS an advantage to counting it as a narcotic gas...

 

[MauiScubaSteve]

As far as "proof" goes, I was watching SciFi channel the other night and on Eureka everyone got narc'd when an experimental O2 generator went haywire!

 

[teejay58]

I too, took the PADI class and was appalled at the multiple guess questions on the test. I was very interested in learning the stuff. I read and studied the book before the class. I listened and asked questions. And I passed with flying colors. But I doubt I will ever dive enriched air. Some of the questions on the test took me a couple of tries before I came up with an answer that was one of the choices. One question in particular, took me about 5 attempts before I found a suitable answer. This is not acceptable. Life on enriched air is not multiple guess and you don't get do-overs. There was no training dive in my class. It was just a couple of hours in a classroom. The things in the class that did make an impression were how easy it would be to die if you miscalculate.

Also, the other two students in the class were a married couple. The wife admitted not reading the book beforehand. She was struggling with the calculations. When it came time to take the test, the instructor left the room. Of course, she turned to her husband and copied his answers. Otherwise, she would've failed. I hope their marriage is long and happy as if she ever dives nitrox, she will not be able to do the calculations without him.

 

[MauiScubaSteve]

Nice first post!

 

[drrich2]

Teejay58:

What did you need a training dive for?

Also, I suspect many Nitrox users use predetermined mixes (mainly EAN 32), with known MOD, and aren't calculating much of anything, just using it like air except setting their dive computers for EAN whatever, and getting more bottom time and/or shorter surface intervals.

And I imagine most mistakes with Nitrox don't result in catastrophic consequences, so most divers in effect do get 'do overs.'

I'm glad you have a healthy respect for the subject, but it seems to've really put you off. Any particular reason you can't just read up in your manual &/or other sources for whatever knowledge you feel is lacking, then dive with EAN when if offers an advantage?

Richard.

 

[grammaticus]

I too, took the PADI class and was appalled at the multiple guess questions on the test. I was very interested in learning the stuff. I read and studied the book before the class. I listened and asked questions. And I passed with flying colors. But I doubt I will ever dive enriched air. Some of the questions on the test took me a couple of tries before I came up with an answer that was one of the choices. One question in particular, took me about 5 attempts before I found a suitable answer. This is not acceptable. Life on enriched air is not multiple guess and you don't get do-overs. There was no training dive in my class. It was just a couple of hours in a classroom. The things in the class that did make an impression were how easy it would be to die if you miscalculate.

Also, the other two students in the class were a married couple. The wife admitted not reading the book beforehand. She was struggling with the calculations. When it came time to take the test, the instructor left the room. Of course, she turned to her husband and copied his answers. Otherwise, she would've failed. I hope their marriage is long and happy as if she ever dives nitrox, she will not be able to do the calculations without him.

My "instructor" also left the class when I took the test. Although I was pretty confident with the calculations, I could have cheated quite easily. Even if you get just within a fraction of the calculation you can guess what the answer is. I also noticed that the book tended not to emphasise enough the fact that you could DIE if you didn't get the calculations right. I suppose that a proper class would have had the instructor instill this knowledge upon his/her students. Anyway...

I dove with nitrox yesterday and I didn't notice a huge difference in "feeling", as many others have, than diving with air. Staying down longer, however, is a perk.

Happy diving and do your calculations properly.

 

[Jax]

Did your instructor not explain maximum operating depth (MOD)?

Best mix?

Equivalent air depth?

These are all things to consider when planning the appropriate EAN mix for a particular dive. If they were not explained in a way that you comprehend why they're important, then the class was not taught properly.

... Bob (Grateful Diver)

I took a PADI nitrox course in 1999, and they explained none of it! It was all about the tables. I bought the TDI Nitrox book and it rocked!

 

[MauiScubaSteve]

Did your instructor not explain maximum operating depth (MOD)?

Best mix?

Equivalent air depth?

These are all things to consider when planning the appropriate EAN mix for a particular dive. If they were not explained in a way that you comprehend why they're important, then the class was not taught properly.

... Bob (Grateful Diver)

I took a PADI nitrox course in 1999, and they explained none of it! It was all about the tables. I bought the TDI Nitrox book and it rocked!

In the PADI system of education, If you; watch the "entire" video, read the "entire" book, attempt "every" knowledge review question, review and understand "every" knowledge review question, ask questions about what you are unsure of, pass the test and review and understand "every" test question you missed, then "best mix" is the only subject that is not covered.

The '95 PADI Enriched Air Diver manual that should have been used in '99 has the following last three questions on the knowledge review;

.....
18. What is the exact EAD for 92 feet using EANx28?
19. What is the exact oxygen partial pressure for 84 feet using EANx29?
20. What are the maximum and contingency depth limits for EANx28?

I have had explained to me and understand the questions I missed.

Student Signature_____________________________ Date__________

The last three sections in the manual are titled;

The Equivalent Air Depth Formula
The Oxygen Partial Pressure Formula
The Maximum Depth Formulas

Directly to the left of each section title is a box titled "Study Objectives" which has 2 questions for each section;

1. Why would you use the;
......................................EAD formula instead of the EAD table?
......................................oxygen partial pressure formula instead of the EAD table?
......................................maximum depth formula instead of the EAD table?

2. How do you use the;
.......................................EAD formula?
.......................................oxygen partial pressure formula?
.......................................maximum depth formulas?

In the Maximum Depth Formulas section there is an entire page long side box titled "What the Formulas Do."

 

[teejay58]

Teejay58:

What did you need a training dive for?

Also, I suspect many Nitrox users use predetermined mixes (mainly EAN 32), with known MOD, and aren't calculating much of anything, just using it like air except setting their dive computers for EAN whatever, and getting more bottom time and/or shorter surface intervals.

And I imagine most mistakes with Nitrox don't result in catastrophic consequences, so most divers in effect do get 'do overs.'

I'm glad you have a healthy respect for the subject, but it seems to've really put you off. Any particular reason you can't just read up in your manual &/or other sources for whatever knowledge you feel is lacking, then dive with EAN when if offers an advantage?

Richard.

well, ya know... I did read the manual. I read it until I thought I understood it. Then I took the class. If reading the manual would bridge the deficiencies, if it would make me confident that I could calculate PPO and MOD without errrors, I wouldn't be so off EAN diving at this point.

EAN diving contains enough risk that it's uncomfortable for me, unless I am completely in mastery of the subject. Being an inland diver, it's rare that I have a reason to go deep enough to use nitrox. And my steel 120's give me 1.5-2 hours bottom time already, on plain air. The time when I would benefit from nitrox would be when i go on vacation and dive wrecks and such. And/or don't have my 120's with me. Vacation happens once or twice a year. And this is not often enough to remember how to calculate EAN dives, or even remember the formulas involved.

If you can use EAN32 like air but you set your computer for it, you aren't using it like air any more. And you are placing your complete trust in an electronic device which could fail. If you don't know where you are on the map of oxygen toxicity, what are you going to do if there is an incident and you have to change your plan on the fly? When i was in class, I frequently wondered if EAN divers took their tables with them underwater. If you accidentally stayed a little long or went a little deep, what do you do?

Yeah, I'm kinda put off EAN. I can easier deal with being bent or air embolism or most anything else other than having a convulsion underwater. I've seen enough and read enough to understand the risk of dying is real in this sport that I love. It just doesn't seem worth it to me, to increase that risk for an extra 10 minutes bottom time.