CESA theory

[Dody]

Dody did a DM course that I believe was done in 2 weeks in Thailand. He had yet to do any night dives. At one place where I dive the same course would have taken 2 - 3 months and you had to lead several night dives. If his DM knowledge is insufficient then perhaps Dody should look at the course he did and wonder if he really got the proper training for his certificate. There are places in SEA that pump out certificates as people want to get certified in the shortest possible time.

You just don’t want to understand and continue assuming that I did not know basic gas law. Pfft! Ok. Let me try to explain what I wanted to know.
You start with x residual volume of air. You are at 30m thus 4 bars.

However, you exhale some air and so you can only assume that x is not equal to 0. At which speed do one exhales, I don’t know the human body well enough to get that but l assumed that one exhales half of what would be consumed normally breathing at the same depth. Let say that your SAC is 10l/ min, breathing would be 40 so you would exhale 20l/min of air at 30 m (the exhale rate, not the calculation, might be completely wrong that’s why I asked in the first place. And I did not even know how to account for CO2 accumulation). This calculation gives you an exhalation volume of 8,75 l ascending from 30 to 20m. While the air would only increase by 5%. This again not taking the CO2 accumulation.

The same logic is applied to the rest of the ascent. So basically, I was stuck with my calculation. And it had nothing to do with ignorance of gas laws. I just could not do the math because of three unknowns in a linear equation.
DO YOU NOW UNDERSTAND?

 

[Dody]

The only judgement I have of you is of insufficient professional knowledge as a DM. I have no particular judgement of you as a person. As to "never insulted anyone trying to help you";





Both of the gentlemen you addressed in the above quotes were trying to bring your attention to knowledge you already have (or should have).... and you snapped at both as though they are fools. They are both respected in this online community, precisely because of the amount of help and knowledge they share here. Literally in less time than you spent typing the insults to them, I googled "residual lung volume" and got you the answers you expected them to spoon feed you.
Again, you list your self with a professional rating. If I can help bridge a gap in knowledge I will help... but it gets awful hard to justify when you attack those who don't do all your research for you.
Please think about trying to request information (and even correct a misunderstanding of what you are looking for) with courtesy.... you are asking for help, and berating those who try doesn't encourage good results.
Respectfully,

James

Those people drew first blood with their multiple comments about gas law ignorance. So I responded harshly as I acknowledged. I am asking for help but I am not begging especially when the so-called helpers don’t understand or don’t want to understand the request. Please read my last post and let me know if most of you were not misled and fixated on something that does not exist.

 

[Blackcrusader]

You just don’t want to understand and continue assuming that I did not know basic gas law. Pfft! Ok. Let me try to explain what I wanted to know.
You start with x residual volume of air. You are at 30m thus 4 bars.

However, you exhale some air and so you can only assume that x is not equal to 0. At which speed do one exhales, I don’t know the human body well enough to get that but l assumed that one exhales half of what would be consumed normally breathing at the same depth. Let say that your SAC is 10l/ min, breathing would be 40 so you would exhale 20l/min of air at 30 m (the exhale rate, not the calculation, might be completely wrong that’s why I asked in the first place. And I did not even know how to account for CO2 accumulation). This calculation gives you an exhalation volume of 8,75 l ascending from 30 to 20m. While the air would only increase by 5%. This again not taking the CO2 accumulation.

The same logic is applied to the rest of the ascent. So basically, I was stuck with my calculation. And it had nothing to do with ignorance of gas laws. I just could not do the math because of three unknowns in a linear equation.
DO YOU NOW UNDERSTAND?

You have tagged me but I never wrote anything about your understanding of gas laws Dody.

 

[Antonios (Holy Diver)]

Truly interesting question.Although I am not qualified to answer the biggest part of it, maybe I can offer a bit of relevant information: At the dawn of Scuba Age (late '40s) the training syllabus for French fleet divers, inspired by Frederick Dumas, required a deep CESA. According to Jacques Cousteau's vivid description: "At the end of the course the honor students swim down to a hundred feet, remove all equipment and return to the surface naked. The baccalaureate is an enjoyable rite. As they soar with their original lungful, the air expands progressively in the journey through lessening pressures, issuing a continuous stream of bubbles from puckered lips." ( Capt.Jacques-Yves Cousteau and Frederick Dumas, The Silent World, National Geographic Society, 2004 edition). The PADI student inside me cringes in fear....

 

[Dody]

You have tagged me but I never wrote anything about your understanding of gas laws Dody.

But the entire thread was about that? Not about diving experience or DM. You guys created it. All I wanted was an answer (maybe complex) to a simple question. What precisely happens in terms of gas during a CESA, step by step. And tou kept coming back at my DM cert and my not having experience. Don’t you think it was ridiculous?

 

[Blackcrusader]

Ok. One thing about first stage. In this case, there was something bursting it seems. Now, 1st stage can just fail blocking all air flow. I know that most should fail open but it happens that it fails closed, right or wrong?

Yes a blown o-ring most likely. But as I wrote, remove the first stage and you can still get gas from the cylinder valve. The tank has plenty of gas in it. It's just how you get any of that gas for yourself. So it does not matter if you have a regulator first stage failure when all you need to do is get gas from the tank. Your OOA situation is not really OOA. If you had an empty tank with no way to get any gas then that is OOA. Shoot air from the tank into any holding device like a DSMB, or trap some air in your wetsuit if you are wearing one for some extra buoyancy. I find I get air bubbles trapped in my clothes on dives and have to release it.

 

[James79]

Those people drew first blood with their multiple comments about gas law ignorance. So I responded harshly as I acknowledged. I am asking for help but I am not begging especially when the so-called helpers don’t understand or don’t want to understand the request. Please read my last post and let me know if most of you were not misled and fixated on something that does not exist.

Nobody asked you to beg. I ask you to be courteous. Your initial question implied a lack of understanding of gas law. When that was brought up, you threw a physics degree in their face and insulted them. Rather than a simple "I get the gas laws, but I don't know where to find the residual lung volume to start my equation from... and does SAC play into it?". See the difference in approach? My wife is fond of the saying "you catch more flys with honey.
Regards the things you seem to have meant to ask:
Residual lung volume: Approximately 1-1.2 liters per wikipedia, varies by individual. All Scuba agencies I know of at least address that there is residual lung volume, even if not addressing the particular amount.
SAC: Non factor... that is based on your normal breathing rate, and in your example you are not breathing normally. You are starting "empty" (greater than residual lung volume because few people fully exhale, but near enough to it) and exhaling as gas expansion allows.
CO2: Really a non issue for the 2 minutes or so it would take to ascend, other than in terms of the CO2 causing the urge to breathe. But even that is reduce due to the continuous exhale helping flush CO2.

Regards the question of DM knowledge. All of the above (except the 15 second google search for residual lung volume) is either directly addressed in OW courses, or a correlation of that information. In Aviation fundamentals of instruction, we have a breakdown of levels of learning... RUAC; Rote (memorized the words), Understanding (I know what the words mean), Application (How to use this specific knowledge), Correlation (I can apply this knowledge to similar situations/data and make the connections between them without being explicitly taught). At the operator level (OW diver), these fundamentals should be at least at the Application level. As a professional, they should be at the Correlation level. That was my concern (And I would guess the concern of others here as well).

James

 

[Blackcrusader]

But the entire thread was about that? Not about diving experience or DM. You guys created it. All I wanted was an answer (maybe complex) to a simple question. What precisely happens in terms of gas during a CESA, step by step. And tou kept coming back at my DM cert and my not having experience. Don’t you think it was ridiculous?

Dody I did not answer the entire thread. The entire thread was not about gas volumes for your CESA. The thread you started never mentions that in your first post. You were concerned about being able to exhale on the ascent. I think you meant 90 seconds not minutes though.

No way would I be able to exhale during 90 minutes starting with my lungs empty

I believe I gave simple answers without being technical about gas volumes for your cesa and I do not recommend doing one. There are other options. If one wants to have some self reflection about being experienced then you need to ask yourself if you really think you got properly trained for the certifications you hold.

DM certified divers should already know the things you are asking. Rescue divers should know this. AOW should know this. That is what others alluded to. Now as to not knowing about rebreathing from a BCD I can understand as it is not taught. In all your training about a failed first stage did nobody cover that there is still air in the tank to be put to good use? After all you are an expert in pipes. tanks. valves, pressures, volumes, gases, and physics outside of diving.

I can't do your physics but I can keep myself from drowning if I lost a first stage and had no buddy close by to assist. At the and of the day that is all that is required. Don't get distracted by some comments. You asked and are learning there is more than one way to get to the surface and keep yourself alive.

Now for CO2 accumulation I wrote on how you can test yourself on that. Get a large plastic bag and put it over your head and seal it as much and possible and rebreathe the air, you need to feel how to control the urge to breathe and make that air last a couple of minutes. It's not hard and it allows you enough time from 30m to get to the surface. If you want you can do a normal exhale and try to calculate how much residual air is still in your lungs as people do not expel all the air under normal breathing.

I don't care about how much volume of air I may or may not have if I need to get to the surface as I would not be wasting time trying to calculate it in the first place. Do you think oh **** first stage failure let me calculate how much gas I have in my lungs at 30m depth? I don't think so.

 

[barth]

Sorry. I forgot to mention that I was not expecting out of context answers like buddy, pony bottle, doubles or whatever. The question is clear. Let’s assume that there is no other solution than CESA. Thank you.

That is not a realistic scenario. If you think that’s a realistic scenario you shouldn’t do the dive.

I don’t think about cesa and do never train for a cesa ascent.

 

[Dody]

Ser

Nobody asked you to beg. I ask you to be courteous. Your initial question implied a lack of understanding of gas law. When that was brought up, you threw a physics degree in their face and insulted them. Rather than a simple "I get the gas laws, but I don't know where to find the residual lung volume to start my equation from... and does SAC play into it?". See the difference in approach? My wife is fond of the saying "you catch more flys with honey.
Regards the things you seem to have meant to ask:
Residual lung volume: Approximately 1-1.2 liters per wikipedia, varies by individual. All Scuba agencies I know of at least address that there is residual lung volume, even if not addressing the particular amount.
SAC: Non factor... that is based on your normal breathing rate, and in your example you are not breathing normally. You are starting "empty" (greater than residual lung volume because few people fully exhale, but near enough to it) and exhaling as gas expansion allows.
CO2: Really a non issue for the 2 minutes or so it would take to ascend, other than in terms of the CO2 causing the urge to breathe. But even that is reduce due to the continuous exhale helping flush CO2.

Regards the question of DM knowledge. All of the above (except the 15 second google search for residual lung volume) is either directly addressed in OW courses, or a correlation of that information. In Aviation fundamentals of instruction, we have a breakdown of levels of learning... RUAC; Rote (memorized the words), Understanding (I know what the words mean), Application (How to use this specific knowledge), Correlation (I can apply this knowledge to similar situations/data and make the connections between them without being explicitly taught). At the operator level (OW diver), these fundamentals should be at least at the Application level. As a professional, they should be at the Correlation level. That was my concern (And I would guess the concern of others here as well).

James

Forgive me but you are the only one who gave me some clues (not the complete answer as the exhale rate, even an average is still unknown) about the initial question so I would not be as optimistic as you believing that any OW could answer it. I would say that most of the instructors would not unless they specifically studied the problem before. I don’t think that the speed of CO2 accumulation, the residual oxygen volume in the body, where it sits (lungs, alveolis or blood), how fast can it get back to the lungs,…) is taught in diving schools even at the highest level. But some divers like yourself don’t just stick to agency manuals . The right answer is much more complicated than it seems. Beyond the theory, I was trying to have numbered scientific data that during a deep CESA, you will not drown.