Gas Analysis

[Kokeldil]

Hellow fellow divers!

I have a question for you which is seriously bugging me ever since I´ve worked through the (basic) Nitrox specialty. During my open water education the instructor just briefly mentioned that there are differences in diving with air and enriched air - not really telling any details though. Then during the nitrox specialty course you get to know that in fact there are very specific dangers in nitrox diving and you cannot do just the same as with air - and in addition to that you learn to analyse your breathing gas.

Now I do wonder why this (gas analysis) isn´s something they teach in the open water course already and beyond that and more important it isn´t something that everyone does every time they get a tank. I mean - after all diving centers which hand out Nitrox as well as air can do mistakes, no? People working there, filling your bottles are just humans, too, after all? Are there any GOOD reasons why it´s really pointless/unnecessary to analyse your breathing gas if it´s told to be "just air"?

I am really excited to read all your opinions on that.

 

[PsyWulf]

Open Water you're taught to NEVER take a Nitrox cylinder ( they should be clearly indicated ). If the shop pumps Nitrox into a regular cylinder well crap

In any Case,the primary risk using EANx is extended periods of use deeper than the Partial Pressure for that mix allows for,regular OW students won't dive deep and long enough to cause any permanent harm I rate

 

[PfcAJ]

If a shop has the capability to fill nitrox, they have the capability to screw the pooch and fill an air tank with nitrox.

Analyze it.

 

[Kokeldil]

[...] If the shop pumps Nitrox into a regular cylinder well crap [...]
[...]regular OW students won't dive deep and long enough to cause any permanent harm I rate[...]

This is exactly the point why I am asking and still wonder why nobody is ever analysing their gas, even if it´s supposed to be air. Shop pumps Nitrox into a regular cylinder. Might be a rare exception but might actually happen, no?
And as for the OW diver not going any deeper than x,y ... yes, student ... we´re talking about certified divers here and right after certification, among the my dives nr. 15 - 50 there have been quite a couple dives deeper than 30m, three even deeper than 40m. So let´s assume I´ve got a EAN36 tank where I assume it to be normal air and my body is not reacting with just nausea and dizziness, but with severe spasms ..... hella dangerous, isn´t it? So why shouldnt we just analyse our gas every freakin time?

 

[tomfcrist]

I would venture to guess it would be possible for a regular cylinder to be filled with nitrox if the shop banks nitrox. For the shops that PP blend, the fill operator would have to be grossly negligent to fill an air tank with O2.

 

[PfcAJ]

Do you really want to roll the dice though?

Reasons for analysis>reasons against.

 

[PsyWulf]

It's a fair point and good to ask. I guess for absolute surety you should test any cylinder from a shop that has nitrox capability to be certain. The NOAA tables for single exposures of EAN had 1.6 Oxygen partial pressure limit of 45minutes for single exposure which was described as quite conservative

The reason it's not taught to rec OW students is it increases the complexity,and unnecessarily so. Many places that do airfills do not have EAN,should everybody learn to test if they might never even see an enriched air cylinder?

 

[ajduplessis]

PfcAJ has it spot on. Always analyze your gas!!

 

[Kokeldil]

It's a fair point and good to ask. I guess for absolute surety you should test any cylinder from a shop that has nitrox capability to be certain. The NOAA tables for single exposures of EAN had 1.6 Oxygen partial pressure limit of 45minutes for single exposure which was described as quite conservative

The reason it's not taught to rec OW students is it increases the complexity,and unnecessarily so. Many places that do airfills do not have EAN,should everybody learn to test if they might never even see an enriched air cylinder?

First off, I for one don´t really consider a ppO2 of 1.6 conservative. This actually should be the absolute maximum. There´s records of incidents at far lower partial pressures.

Secondly, I am well aware that all this only adds unnecessary complexity to a basic diving education and can imagine why it´s not taught in an OW course.

HOWEVER .. as you can see even (or out of all) the expierienced divers seem to tend to "always analyse" in this thread so far. Kind of on the same page as I am. I admit never having done it when provided normal air, but that was merely for not wanting to make myself look stupid at the center. You guys however give me good reason to insist on analysis in the future - even for air tanks. Thanks so far.

And on a sidenote - yes, so this all is in fact good reason to let an OW student at least know about the possibilty to HAVE their gas analysed by someone at the center before they use a tank.

 

[PsyWulf]

First off, I for one don´t really consider a ppO2 of 1.6 conservative. This actually should be the absolute maximum. There´s records of incidents at far lower partial pressures.

There will always be exceptions of course,just saying that 1.6 isn't necessarily a killzone,or even a guaranteed bad time. My last trip to Sodwana we had some OW kids nab our EAN32 cylinders and dive unknowingly on EAN,we gave them a thorough dressing down but otherwise they were okay.

Secondly, I am well aware that all this only adds unnecessary complexity to a basic diving education and can imagine why it´s not taught in an OW course.

HOWEVER .. as you can see even (or out of all) the expierienced divers seem to tend to "always analyse" in this thread so far. Kind of on the same page as I am. I admit never having done it when provided normal air, but that was merely for not wanting to make myself look stupid at the center. You guys however give me good reason to insist on analysis in the future - even for air tanks. Thanks so far.

We minimize or lessen risks by being anal about these things,it only takes one error to possibly kill you

And on a sidenote - yes, so this all is in fact good reason to let an OW student at least know about the possibilty to HAVE their gas analysed by someone at the center before they use a tank.

Aye its definitely a consideration for schools to teach basics or at least warn without scaring them,I've added this to my list when i'm finished with my Instructors