Should you be diving NITROX if you can not answer these questions?

[lamont]

Either they are lying about their certifications, or the shop/instructor needed an extra couple of bucks and that's why they were passed...

Ken

They could have been certified ages ago. NOAA Nitrox I (32%) was chosen to hit its 1.6 MOD at 130 fsw to match up with the limits of rec/NDL diving. Since then the MOD limits have tightened up to 1.4 and with some agencies recommending no more than 1.2

 

[scubadiver888]

Some snippets from another thread - all posts were made by three different people all of which are NITROX certified. The third post is mine which is combination of two posts.


First Post - "I was diving ... at 1.6 ppo (130?)"

Second Post - " ... what where YOU doing at 130 ft on NITROX? What was your %? If you planned on going THAT deep, why use nitrox? What was the benefit of nitrox at that depth?

Third Post - "Do the math, the first post contains all of the information needed to figure out the mix. As for using NITROX at 130 feet there is nothing wrong with it and the benefits to diving NITROX at 130 feet are the same and more as diving it at 60 feet. If you do not know this or can not do the math you should not be diving NITROX"

Several people did not get my post - what I found odd was that these posts were part of a larger accident discussion on this board where many people were stressing personal responsibility in the context of a person who had some knowledge but perhaps not enough to not keep/get themselves out of trouble. Yet IMHO the second post shows someone who has had the training yet still fails to have the knowledge.

So if you are nitrox certified could you answer the questions to the second post without looking them up? Please do not post the answers as they are not german to the thread and might prevent someone from realizing they need a refresher course.

If I know two of the three (ppo, depth, %) I can figure out the missing value. I would expect everyone who has had nitrox training to be able to do this as well.

HOWEVER, the PADI training (imperial) tells you to memorize the magic numbers 46.2 and 52.8. If they taught it as (1.4 * 33) and (1.6 * 33) it would be easier to remember. I've met numerous people trained by PADI (including the instructors) who didn't know what the numbers 46.2 and 52.8 represented. The instructors had however memorized the numbers and could do the calculations without looking them up and expected their students to do the same.

 

[rstofer]

They could have been certified ages ago. NOAA Nitrox I (32%) was chosen to hit its 1.6 MOD at 130 fsw to match up with the limits of rec/NDL diving. Since then the MOD limits have tightened up to 1.4 and with some agencies recommending no more than 1.2

Which agencies are recommending 1.2? I would like to read what they have to say and decide if I want to back off of 1.4. I would be even more interested in reading their reference studies and other justification.

Richard

 

[scubadiver888]

To be honest...

I'm newly certified for Nitrox (03/14/09), haven't dove on it yet and couldn't pull the answer out of thin air as I don't have the formulas memorized.

I can however get the answer using the tables I have and if I want it quicker I can pull-up iScuba Plan on my iPhone and plug in the numbers to get a "close enough" answer (as iScuba Plan does EAN in integers only).

I will say that when I do start using Nitrox I will definately know the depth limit of my Mix and have my computer set to warn me BEFORE I reach it.

kyphur,

If you were taught properly you should be able to figure things out without a special program. If you understand things it should just all make sense. It is not about memorizing formulas. I never remember the formulas. I remember the physics behind it and create the formulas from that knowledge.

If the formulas don't just make sense you should go back to your manuals or instructor and figure it all out. It really is easy to remember if you understand why things are the way they are.

Darrell

 

[lamont]

Which agencies are recommending 1.2? I would like to read what they have to say and decide if I want to back off of 1.4. I would be even more interested in reading their reference studies and other justification.

Richard

GUE, recommends bottom ppO2s of 1.2, but they're primarily a technical diving agency.

At that level it makes a lot more sense since you'll be running 1.6 ppO2 later in the dive, not as clear to me that it makes as much sense with recreational diving...

...

And on the topic of way-back-when... I believe it used to be practice to run 1.8 ppO2s and do deco on 2.0 - you can look into studies where that is clearly running a higher risk though... That was practice back when divers didn't know any better....

 

[rustyshakelford]

rusty - if your reply is genuine please reread your books.

I was just messing around. when i plan my dives and decide what mix to dive, Ill plan a ppo of 1.4-1.5 and go onto deco gas at 1.6 for 50% or 100%

So will I... air enriched with helium.

Hopefully, i can be doing the same by the end of the year!

brett

I think i gained a much better understanding of nitrox in my adv nitrox class over my padi enriched air class. Im sure thats the point, or maybe the intial instruction was poor im finding myself more and more preaching the benefits of nitrox to the guys i work with

 

[rstofer]

PADI Nitrox wiz-bang doesn't count.

What specifically does PADI fail to teach? More to the point, what agency teaches anything beyond what PADI teaches? Is there a facet of Nitrox diving that PADI doesn't cover?

True, I only know what I have been taught but it seems pretty thorough to me. I know how to calculate MOD (although I carry a table in my wallet), I understand the depth limitations, I know how to analyze my gas and I understand the tables. Thoroughly!

Nitrox has a few considerations beyond air diving but they are pretty simple to learn. It ain't differential equations... At least not in application.

Richard

 

[ScubaSteve]

First Post - "I was diving ... at 1.6 ppo (130?)"

Second Post - " ... what where YOU doing at 130 ft on NITROX? What was your %? If you planned on going THAT deep, why use nitrox? What was the benefit of nitrox at that depth?

Third Post - "Do the math, the first post contains all of the information needed to figure out the mix. As for using NITROX at 130 feet there is nothing wrong with it and the benefits to diving NITROX at 130 feet are the same and more as diving it at 60 feet. If you do not know this or can not do the math you should not be diving NITROX"

The issue I have here is that you are claiming that all we need to do is to calulate the percentage mix using the information present. While that is possible, iot DOES NOT answer the question that was asked. The question that was asked was "What was your %?". Your formula arrives at a percentage but NOT the percentage used by the person quoted with the first quote. You are assuming that the person first quoted was diving a proper plan and was not exceeding MOD.....not necessarily a safe assumption. This was all listed in that thread but got deleted at the same time as your posts .

So, your question really proves absolutely nothing to do with the previous thread or anything about the people involved in it.

 

[rstofer]

GUE, recommends bottom ppO2s of 1.2, but they're primarily a technical diving agency.

At that level it makes a lot more sense since you'll be running 1.6 ppO2 later in the dive, not as clear to me that it makes as much sense with recreational diving...

...

And on the topic of way-back-when... I believe it used to be practice to run 1.8 ppO2s and do deco on 2.0 - you can look into studies where that is clearly running a higher risk though... That was practice back when divers didn't know any better....

Ah, context... I only think in terms of recreational diving because that is the limit of my skills. Tech divers do all kinds of strange things. Far above my pay grade...

I recall the 2.0 number from my NAUI training in '88. It put a depth limit on diving with air - somewhere around 280 feet. I wasn't planning to dive that deep so I put the number in the 'I don't need to know this' bin.

Richard

 

[Scared Silly]

The issue I have here is that you are claiming that all we need to do is to calulate the percentage mix using the information present. While that is possible, it DOES NOT answer the question that was asked. The question that was asked was "What was your %?". Your formula arrives at a percentage but NOT the percentage used by the person quoted with the first quote. You are assuming that the person first quoted was diving a proper plan and was not exceeding MOD.....not necessarily a safe assumption. This was all listed in that thread but got deleted at the same time as your posts .

So, your question really proves absolutely nothing to do with the previous thread or anything about the people involved in it.

Steve, we might have to agree to disagree here. I made no assumptions about the person's dive plan and whether they were following it or not. The first post me gave a depth and a PPO2 for that depth for the mix he was using. Which is enough to figure out what mix he was using. You may be be interpreting it differently which is fine. Regardless though the rest of the questions from the second post should be something that someone trained in using using nitrox should know. Which is really my point.

Edit - my one assumption is that the diver hit 130 feet and his computer gave him a PPO2 violation warning. Most people with computers set them for a working PPO2 of 1.4 and a max of 1.6. Which is why he knew the PPO2 at 130 feet was 1.6.