Quiz - Physics - Partial Pressure of Carbon Monoxide

[Ukmc]

And a reflection of how little thought that Padi gives the risk, I think.

@DandyDon are you a real person or several people? You are responding on the board at all the different times and all the time it is like you do not sleep

 

[DandyDon]

@DandyDon are you a real person or several people? You are responding on the board at all the different times and all the time it is like you do not sleep

Oh, to answer your interesting question, I'm just an old coot with too much time on my hands, more so during mandated Stay-Home isolation.

 

[GJC]

Well, what I learned in DM course must be wrong. I learned that due to increased pressure at depth resulting in more O2 in the plasma, life can be supported. With the decreased pressure upon ascent, that is when people with CO contaminated tanks will pass out--usually all pretty close to the same time if they have the same tank contents.

That could only happen in a very unique set of circumstances. You must have narrow percentage range of your hemoglobin blocked by CO so that the O2 on the hemoglobin plus that dissolved in plasma is just enough to keep you conscious, so that as you ascend the O2 in plasma drops enough to make you unconscious. Too much hemoglobin blocked and you pass out at depth. Too little hemoglobin blocked and you stay conscious all the way to the surface.

You would need a very specialized dive table or computer that would figure it out based on CO in breathing gas, depth, dive time, how much hemoglobin your body had and your oxygen consumption rate (how hard you are working).

Perhaps there is a market for a new dive certification. CO Diver. You would certainly need a CO analyzer and a CO dive computer.

 

[DandyDon]

You would need a very specialized dive table or computer that would figure it out based on CO in breathing gas, depth, dive time, how much hemoglobin your body had and your oxygen consumption rate (how hard you are working).

The molecule is too different from O2 and N2 that I don't think that could ever be defined. CO is even produced by healthy people, works as a signaling gas, and a lot more that I will never understand. Some major breakthroughs in understanding all of this may be forthcoming and studying other planets and their gases may help, but it's basically a VoodDoo gas to avoid in everyday life and diving.

With the agencies, DAN, and the fill stations still not doing much, there's only one safe way to deal with it. Test every tank and only dive the safe ones.

 

[GJC]

The molecule is too different from O2 and N2 that I don't think that could ever be defined. CO is even produced by healthy people, works as a signaling gas, and a lot more that I will never understand. Some major breakthroughs in understanding all of this may be forthcoming and studying other planets and their gases may help, but it's basically a VoodDoo gas to avoid in everyday life and diving.

With the agencies, DAN, and the fill stations still not doing much, there's only one safe way to deal with it. Test every tank and only dive the safe ones.

Absolutley!

Perhaps we could gain more traction on this with a CO Free diver certification with a CO monitor given out for every student.

 

[Angelo Farina]

In any case, all this discussion just proofs my point: the effect of breathing CO at 5x higher p.p. at depths cannot be simply assumed to be the same as breathing CO at 5x percentage at surface.
So the supposed "right" answer (7.5%) is definitely not right, in my opinion.
The effect will be definitely bad, so I do not see how to find volunteers exposing themselves to such toxic gas mixtures just for evaluating which is the real equivalence between increased p.p. ad depth and increased percentage at surface.
It is a wrong question, and the only correct answer would be "no one knows"...

 

[johndiver999]

Yes, sorta like.. When bench pressing 3600 kg, is it better to use a narrow or wide grip?

 

[BlueTrin]

Yes, sorta like.. When bench pressing 3600 kg, is it better to use a narrow or wide grip?

It’s probably better for me to use YOUR grip in this case

 

[RayfromTX]

CO in a tank of breathing gas is also an indicator that something isn't right. You aren't testing for combustion byproducts but the CO is an indicator that they may be there and they may be toxic in and of themselves. I don't take a tank down with more than 5 ppm and if there is a choice I won't dive that. If I'm going to 40 meters, I would "probably" refuse the 5ppm tank even though the 25ppm for the time I would spend at that depth would in no way threaten my health on its own. Smokers exhale ~17ppm when they aren't smoking and non-smokers exhale ~3ppm so I wouldn't consider 5ppm as a problem to a healthy(nonsmoking) individual on it's own.

The wording of the question is unfortunate. It is all too common in all the agencies that the teaching materials seem to be poorly proofread before publishing. I have found things like this in the 4 agencies that I have taken training from. (one of them I have only read the materials from and not gone forward with actual training)

 

[craig_perth]

1. That level of CO is very quickly fatal at surface pressure let alone depth. A diver would not survive long enough to get to 40m.

2. If it is 1.5% concentration, it will be 1.5% concentration at any pressure. It will be 1.5% in the tank at 200 bar, the various gasses all come out of the tank in the same relative concentrations as they exist in the tank. ( Trust me on this I am an engineer.)

3. What will change is the partial pressure of the gas concerned.

4. At 40 m the pressure is 5 bar 40/10+1=5 That is one bar surface pressure plus one for every 10 m depth. The partial pressure at depth will then be 5 times the partial pressure at the surface. If we have a regular air tank 21% O the partial pressure at the surface of the O is 21%, at depth it is 5x0.21=1.05 bar. If Nitrox at 40% it is 5x0.4=2 which is ijn the O toxicity range.

5. At 40 m the diver would have his lifeless body exposed to 5 times as many CO molecules as at the surface in every dying breath, but since all other gas molecules would still be 5 times as many, the percentage is the same with no regard for depth.

6. That is a really dumb exam question, it is looking for a partial pressure type of answer but expresses it in percentage terms, uses a fatal level of the gas mentioned when the same logic would apply to any gas in the tank. They could have just as easily said some inert gas in the tank. I don't think the writer of the question has any idea what they are actually writing about.

6. The guy who wrote the question deserves to be fired, his supervisor who approved the question deserves to be given a tank of 1.5% CO to demonstrate how dumb the question really was.

I 100% agree with you on this. 1.5% is 1.5% at any depth.
Its like having 32% mix at the surface, this percentage at any depth is still 32% is the partial pressure that changes. The question should read ".......it would have the same effect as breathing _________ partial pressure or ata or something along those lines.

I have taken this up with some agencies, however never hear anything back. Yet in all exams the "correct" answer remains 7.5, which it is not.