Slightrox and shenanigans!

[northernone]

In honor of boulderJohn's coined term here's a thread on near normoxic enriched air nitrox mixes.

After a EAN fill when do you go back to considering the mix after multiple top-ups to be normoxia and call it straight air or do you log it as EAN until the next full drain and refill? Technically, even analysing as similar to air, it's still enriched and a mix?

Here's the fun part. Padi requires 10 (or 20 enriched air nitrox logged dives) to become a nitrox speciality instructor.

I didn't do my MSDT specialties kit until I had a respectable number of nitrox dives but it begs the question.

Some places nitrox is expensive or unavailable and it would be convenient to treat near normoxic nitrox (air plus a EAN fill residue) as EAN to again experience planning dives.

Another glitch, my dive computer (nemo wide) has an air mode or an EAN mode... you can't switch between them immediately following a dive, so I leave it on EAN and tell it air is 21% ean so it stays happy if I'm switching mixes between dives.


Anyway, cheers to a great term and a happy Sunday to you all!

-Cameron

 

[tbone1004]

uhhhh rather perplexed by what you're trying to get at? Everything gets analyzed and input into computer/plan/log at whatever mix the analyzer says it is. If it is anything greater than 20.9% O2, then it is enriched air nitrox and is treated as such.

You brought up an EANx fill with air topoffs, why would that not count as an EANx dive until such a time that the O2 reads out at 20.9%.

My compuer doesn't have any "modes" for different gas mixes, you just tell it what you're diving, but if you can set your EAN mode at 21% then I wouldn't ever put it in air mode....

 

[northernone]

I reread my post, I apologize it's quite rambling.

I agree EANx is EAN until it analyzes to normoxia.

I'm questioning it since I had a insta buddy laugh at my EAN24 log and tell me to call an air fill what it is, air.

Thanks for digging through the silt to reply!
Cameron

 

[tbone1004]

I reread my post, I apologize it's quite rambling.

I agree EANx is EAN until it analyzes to normoxia.

I'm questioning it since I had a insta buddy laugh at my EAN24 log and tell me to call an air fill what it is, air.

Thanks for digging through the silt to reply!
Cameron

You dove EAN24, treat it like EAN24.... Now if I had a computer that was annoying to change gas mixes I would probably just dive it as air unless you are diving for multiple hours where you would actually have some sort of decompression benefit from changing the mix, but for recreational NDL diving it doesn't matter and your instabuddy has a point. EAN24 isn't an "ideal" gas due to depth, and if you are not pushing NDL's, and even if you are, EAN21 vs EAN24 isn't going to result in that much if a difference, so I would probably just leave it set on air and call it a day because I'm lazy. I certainly wouldn't call anyone out for adjusting their computer to represent what they were actually breathing.... that's silly

 

[DevonDiver]

After a EAN fill when do you go back to considering the mix after multiple top-ups to be normoxia and call it straight air....

Firstly... the word 'normoxic' generally has a very different usage in diving... for trimix mixes. It means a trimix blend >18% O2 that is breathable from the surface, as opposed to hypoxic.... mixes which have less than 18% oxygen. Normoxic is determined by the partial pressure of oxygen being sufficiently capable of sustaining consciousness/life at 1 atm.

That's an issue of diving terminology/parlance, rather than dictionary definitions.

We can call a gas mix "straight air" when it is straight air - that being it is 21% Oxygen / 79% Nitrogen.

Any mix with more than 21% Oxygen isn't air...it is 'enriched air' and standard nitrox diving procedures should apply.

or do you log it as EAN until the next full drain and refill? Technically, even analysing as similar to air, it's still enriched and a mix?

If you analyze the cylinder and it is 21% oxygen, then you can consider it as air. Anything beyond that is 'enriched air'. It doesn't matter whether a richer mix has been diluted over numerous re-fills, or whether you drained and re-filled the tank. What matters is the analysis.

You can even consider 21% oxygen / 79% nitrogen as nitrox if you wanted. It's EANx21. I am breathing it now, here on my couch.

Here's the fun part. Padi requires 10 (or 20 enriched air nitrox logged dives) to become a nitrox speciality instructor. I didn't do my MSDT specialties kit until I had a respectable number of nitrox dives but it begs the question.

Which question? Can you fudge air dives as nitrox dives in your log book to short-cut the principle of gaining some tiny amount of experience before teaching that subject to others?

Some places nitrox is expensive or unavailable and it would be convenient to treat near normoxic nitrox (air plus a EAN fill residue) as EAN to again experience planning dives.

If nitrox is expensive or unavailable, how would you teach it anyway?

Seriously... instructors should have EXPERTISE.

Of course.... some agencies have made the nitrox course incredibly easy.... and all the theory can be done online. That leaves 'nitrox' instructors with only the onerous task of supervising students whilst they analyze a tank... then issuing a certification.

If someone can make money out of doing just that.... fair deal.... and I don't see why the agencies concerned would even ask for 25 dives experience for an instructor rating...

Because, after the student completes eLearning.... all the 'experience' that an instructor really needs is 5 minutes to read and learn the instruction manual of the nitrox analyser to be used..... but then again.... isn't that all the poor student needs also...??

Cameron... here's some hypothetical questions:

If an eager student enrolled on a nitrox course....and asked the instructor how to calculate MOD, EAD or Best Mix with only a pencil and paper.... should they be able to teach them that?

If an eager nitrox student asked their instructor on what occasions they have used nitrox... and what mixes were chosen.... for what dive parameters....and why.... should they be able to answer that in way that adds educational value?

If an eager student asked about dive computers and "slightrox"... could the instructor answer them from personal experience... or because they'd read about it on a forum. What if the student had read the same forum?

The point being... the student can learn 'the manual' from paper or eLearning... their subsequent time with an instructor (which they pay for....) should empower further learning beyond the basic text. That learning stems only from the instructor's experience.

 

[northernone]

I appreciate the in depth reply.

Good point about dictionary term, I don't talk to enough divers to have the right usage yet.

It's hard to agree with your regarding EXPERTISE since I'm part of the problem you describe. However, you are right. I'll get there eventually.

Regarding your question, thankfully yes I'm getting there about mod, ead and best mix long hand. That's only because I'm a math head and I had a dive buddy in his 6th decade diving take the time to guide me through to do paper dive planning. I was able to pass this on to my brother (don't we love relatives to be guinea pigs) without too much agony... it helps he is brilliant I must admit.

In full disclosure my own -dive agency- EAN certification consisted of reading the manual, writing questions and analyzing two tanks.... all in all I was 25 minutes start to finish including my credit card info.... slightly scary what the minimum standard is. Anyway, I'm thankful for experienced fellow divers and that I didn't live with the illusion I was 'trained to proficiency' when I bought my cert card

As for the reason to teach where ean isn't available easily... In my context the nearest fill station is 600 miles, but I can imagine eventually a diver (if there are active local divers here) might want to be nitrox trained before a vacation dive where nitrox is required.

It would be useful to have be able to do decent training (not just stimulate and pay) but not needing to haul a ton of bottles or invest in maintaining o2 cleaned bottles and a pp blend station, bank and booster or a nitrox stick.

Thinking about it, I'll stick with EAN22 being nitrox and drop when I hit 21% call it air.

Interesting to think about, though the actual practical advantages aren't evident with these mixed.... And I've never heard of a diver who would bother with blending a best mix at 22% no matter what the math says.

 

[EricTheDood]

You should log your dives based on what you're breathing. If your computer doesn't like it, it might be time to get a new computer. When I download my dive logs to my desktop, it shows some form of the NDL at any given point during the dive. In my case, with Suunto DM5 software, they label it "tissue saturation", which is the % of N or He as well as the rate of absorption, and it changes constantly throughout the dive profile. YMMV but I'm sure other programs have something similar.

Any blend of Nitrox affects NDL, so it's useful as learning and a teaching tool to accurately record and analyze your dive logs, even if you're just using EAN24 from an air top off.

Perhaps it's also important not to treat EAN24 like air due to potential oxygen toxicity issues. Even if the practical differences may be marginal, it's just not a good idea to practice short cuts, much less teach them.

When your tank's air dips below 22% O2, that's a different story. Your O2 analyzer might only be accurate to +/- 1%, so there's no point in recording data at a resolution finer than the accuracy of the measuring instrument.

 

[DevonDiver]

It's hard to agree with your regarding EXPERTISE since I'm part of the problem you describe.

If there's a problem, it stems from agencies - not instructors. It is, after all, the agencies which lower the bar and encourage instructors to teach. In defense of those agencies, courses are 'from the box'... and (the way I see it) the instructor is there to deliver a product and verify it's been understood 'satisfactorily'... rather than actually educate and teach people to become divers. Expertise doesn't come into it...

When it comes to instructors... I agree there's a lot of temptation because the agencies are right there slapping you on the back and telling you what you could do (to make more money). Instructors have to put food on the table....

That's where professional ethics and personal standards come into it... your honesty and commitment to your students... in what you personally have to offer them... to make them into better divers. That's where expertise matters.

What an agency says you could do.... and what you should do.... can be different.

If students are running around getting the cheapest quotes for "a card"... then they aren't demanding expertise. They're simply shopping for a plastic license. There's no ethical conundrum with providing the minimum to someone who wants the minimum.

But if a student is looking for training...for real improvement... for skills... for knowledge...for coaching... then they are expecting expertise from an instructor. It's only fair and right that they should receive that....

In full disclosure my own -dive agency- EAN certification consisted of reading the manual, writing questions and analyzing two tanks.... all in all I was 25 minutes start to finish including my credit card info.... slightly scary what the minimum standard is.

It wasn't THAT long ago that the PADI EANx course was a 2-day affair... mandatory dives and a 2-part exam with maths questions... that got condensed down to a half-day course (including providing credit card info). It was a good course... and many found it (intellectually) challenging.

For the majority of divers, I don't think that's better or worse...it gives them all they need to safely dive EANx... assuming computers, simple dive profiles and responsible gas vendors/dive centers. Given that most recreational divers only dive on vacation...and are limited by consumption, not bottom-time... using simple EANx32 or EANx36...following around a DM in a herd.... it's the right course for the right market.

It falls short for those with a genuine interest though.... for people who want more than just a 'ticket' to use nitrox... but actually want to learn more about the theory and practice of diving... or may intend more ambitious dives using best mixes for depth etc...

And, of course... EANx is a prerequisite for technical training, The tech courses expect knowledge in line with the old course from entry level tech divers. The new course falls woefully short of that... and those divers are left in a remedial situation when tech training starts...

As for the reason to teach where ean isn't available easily... In my context the nearest fill station is 600 miles,

As a new instructor.... identify that as a big gap in the market. Do a Gas Blender course.... rig up a very simple partial pressure filling set-up... sell nitrox, sell nitrox courses... That's expertise (and not nearly as complicated or costly as you might imagine)

It would be useful to have be able to do decent training (not just stimulate and pay) but not needing to haul a ton of bottles or invest in maintaining o2 cleaned bottles and a pp blend station, bank and booster or a nitrox stick.

1x bottle medical oxygen, available anywhere (like LPG, deposit on the bottle, gas is cheap)
1x whip (to run from oxygen bottle to diving cylinder)
O2 clean tanks (see Gas Blender course....)
Top up with air from an O2 clean compressor (there must be a O2 clean compressor around?)

 

[tbone1004]

that's because when 22% becomes the "best mix" for O2 levels *~50m/170ft*, a level of helium is required in order to reduce nitrogen narcosis *typically somewhere between 35%-45%* but that's another discussion. Typical gas you'd see there at least following standard gasses is 21/35 or 18/45.

Nothing less than 32% really makes sense to me because anything deeper than the 111ft MOD of 32% is trimix territory for me. I dive air when I'm diving short dives and it's cheap/free, and 32% if I don't want to incur a lot of decompression. Anything less than 32% as an intentional fill is a waste imho, and anything more than that is also a waste unless you are trying to max out NDL's, which I don't care about because I am deco certified, so getting an extra 5 minutes of bottom time doesn't matter to me because my 5 minute "safety stop" will become maybe a 7 minute mandatory deco stop depending on which gradient factors I'm using. Not a huge deal to me.

Regarding the math, it's all incredibly simple if you understand the relationships between depth and partial pressures. The problem is very few agencies and instructors are good at teaching this relationship and most peoples/instructors understanding of nitrox math is the lowest form of learning, memorization.... I sit somewhere in the middle on how I think nitrox should be taught. You should be able to do all of the math if the cert says you are certified to dive any mix, not just "standard mixes" of 32% or 36%, but you shouldn't have to go diving because you aren't going to get anything from the dives related to nitrox. You may or may not get anything from being in the water with that particular instructor, but whatever you get is going to have nothing to do with you diving nitrox or not.

 

[Storker]

anything deeper than the 111ft MOD of 32% is trimix territory for me.

That's because you're trimix certified. Quite a few non-trimix-certified divers go to 40m/130', where EAN32... isn't recommended. That's where EAN28 comes in handy for those who are fine with going to 40m/130' (or deeper) without any He in their mix.

Disclaimer: I'm not one of those divers, but I know a few.