Very deep dives inflation gas choice - risk of skin bends for Rebreather dives

Drmike · 4th May 2006, 15:17

Quote: (Originally Posted by Peter Steinhoff)

at increased depth the CLO value of the underwear decreases which would make the gas properties proportionally more significant.

If the inside of the suit is at ambient why would the underwear CLO value decrease?

Peter Steinhoff · 4th May 2006, 16:48

Quote: (Originally Posted by Drmike)

If the inside of the suit is at ambient why would the underwear CLO value decrease?

There is a pressure differential inside the suit since the gas want to rise. For instance when you are riding a scooter your hand and arm are more squezed. Also a difference beteen breast and back. Small but enough to make a difference. There are some tests on 3Ms thinsulate where they tested it at different pressures and got different CLOs. I don't know however if the fibers themselves are subject to any compression depending on the absolute pressure.

Peter

Drmike · 4th May 2006, 17:15

Quote: (Originally Posted by Peter Steinhoff)

There is a pressure differential inside the suit since the gas want to rise. For instance when you are riding a scooter your hand and arm are more squezed. Also a difference beteen breast and back. Small but enough to make a difference. There are some tests on 3Ms thinsulate where they tested it at different pressures and got different CLOs. I don't know however if the fibers themselves are subject to any compression depending on the absolute pressure.

Peter

Surely you would have the same difference between chest and back at any depth for the same amount of comfortable squeeze?

Put a piece of undergarment into a sealed container and pressurise it. Why would its COL value change? For it to change the material must be crushed. To do that a differential would have to exist the deeper you go. But in reality the diver controls the degree of inflation (differential) in his suit to what is comfortable at all depths. So I cant see how that can be. For the undergarment to crush more at depth the suit would need to crush more and so the diver would be in more pain...which he isnt...because he removes the differential (squeeze) by adding inflation gas.

I can see that it is different with a wetsuit where the air bubbles in the neoprene are crushed - but thats only beacuse the diver cant make up for that by adding more air into the neoprene air bubbles the way he can add air into a suit to get rid of the squeeze

....its a quiet night

Peter Steinhoff · 4th May 2006, 20:02

Quote: (Originally Posted by Drmike)

Surely you would have the same difference between chest and back at any depth for the same amount of comfortable squeeze?

Put a piece of undergarment into a sealed container and pressurise it. Why would its COL value change? For it to change the material must be crushed. To do that a differential would have to exist the deeper you go. But in reality the diver controls the degree of inflation (differential) in his suit to what is comfortable at all depths. So I cant see how that can be. For the undergarment to crush more at depth the suit would need to crush more and so the diver would be in more pain...which he isnt...because he removes the differential (squeeze) by adding inflation gas.

I can see that it is different with a wetsuit where the air bubbles in the neoprene are crushed - but thats only beacuse the diver cant make up for that by adding more air into the neoprene air bubbles the way he can add air into a suit to get rid of the squeeze

....its a quiet night

Mike, I don't know and neither do you, and that is my point. You are just guessing...

Maybe a large portion of the small thinsulate fibers are welded shut during manufacturing and act as pressure containers. Regarding the pressure maybe I should have used the word compression as if you press it together. When the fibers are more compressed, which they are on some body parts compared to other, their thermal characteristics change because the fibers are closer to each other.

Also diving an Rebreather compared to OC would be different because you don't have the same cooling effect (increasing with increasing depth) from the breathing gas. That means you now loose a larger proportion of your heat from your body. And then at depth we also have the effects of increased CO2 production (gas density) and nitrogen narcosis that could change our bodies thermal response.

There are simply too many factors to draw the general conclusion that argon would not make a measurable difference to air in all diving scenarios. If we only look at the gases physical properties argon IS a better insulator than air.

Would love to continue this discussion but I got take off for 2 weeks of intense cave diving.

Regards,
Peter

dteubner · 5th May 2006, 00:52

Quote: (Originally Posted by Peter Steinhoff)

Simon,

First of all I would imagine everyone being in agreement that gas properties do make a difference? Everyone in doubt are free to conduct a dive with a high helium gasmix as a drysuit inflation gas and tell us your empirical findings. Peter

The diffence in conductivity of helium and air is over 6 fold, between air and argon about 1.3 fold. It's hardly the same thing.

It's all about levels of evidence isn't it.

Anecdotal evidence - "this thing that I have spent time and money and effort on makes me feel warmer"

Theoretical evidence - "There is a small difference in a parameter that should make a difference to how warm I feel"

Scientific evidnece - "An extremely well designed and conducted study showed no differrence"

But the scientific evidence is in conflict with the anecdotal evidence - therefore the scientific evidence must be wrong. Flawed study design maybe?

Dave T

Drmike · 5th May 2006, 03:13

Quote: (Originally Posted by Peter Steinhoff)

Mike, I don't know and neither do you, and that is my point. You are just guessing...

Maybe a large portion of the small thinsulate fibers are welded shut during manufacturing and act as pressure containers. Regarding the pressure maybe I should have used the word compression as if you press it together. When the fibers are more compressed, which they are on some body parts compared to other, their thermal characteristics change because the fibers are closer to each other.

Also diving an Rebreather compared to OC would be different because you don't have the same cooling effect (increasing with increasing depth) from the breathing gas. That means you now loose a larger proportion of your heat from your body. And then at depth we also have the effects of increased CO2 production (gas density) and nitrogen narcosis that could change our bodies thermal response.

There are simply too many factors to draw the general conclusion that argon would not make a measurable difference to air in all diving scenarios. If we only look at the gases physical properties argon IS a better insulator than air.

Would love to continue this discussion but I got take off for 2 weeks of intense cave diving.

Regards,
Peter

Actually I do know, and wasnt guessing - I was just being polite.

Have fun with your intense cave diving. I will be doing a bit of cave exploration myself from end of next week.

nothing too intense

steevke · 5th May 2006, 05:24

Quote: (Originally Posted by dteubner)

The diffence in conductivity of helium and air is over 6 fold, between air and argon about 1.3 fold.

And this 1.30 factor is for STILL and DRY air compared to argon.

In reality, when diving the gas in your drysuit will not be still nor completely dry, so the theoretical 1.30 advantage is likely to be much LOWER in reality.

Steven

Sponge-Bob · 23rd November 2006, 23:01

Hi,
I've used Argon and Air for suit inflation on extremely deep dives.

Personally I think Argon is probably a placebo. I always found a suit heater works better!

Personally I always opt for Air and have never had problems.

Just don't even think of using your bottom mix

My policy also is don't carry anything that can't be breathed, but then again air at 200m isn't goint to do you much good anyway!

But I make sure that my suit inflation can be crosspatched into everything just in case I ever need it.

But hey, don't trust me. Go with the science! Your a test pilot at those depths anyway.

Stay safe...

graham_hk · 24th November 2006, 04:42

Quote: (Originally Posted by steevke)

And this 1.30 factor is for STILL and DRY air compared to argon.

In reality, when diving the gas in your drysuit will not be still nor completely dry, so the theoretical 1.30 advantage is likely to be much LOWER in reality.

Steven

True but then the value for Argon is for still and dry and therefore when it is your suit it will increase just like air will so you would still have the 30% increase. Whether it makes a difference - well you'll have to make your own mind up

Graham

4th May 2006, 15:17	#21 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,157	Re: Very deep dives inflation gas choice - risk of skin bends for Rebreather dives Quote: (Originally Posted by Peter Steinhoff) at increased depth the CLO value of the underwear decreases which would make the gas properties proportionally more significant. If the inside of the suit is at ambient why would the underwear CLO value decrease? __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
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4th May 2006, 16:48	#22 (permalink)
Peter Steinhoff New Member Current Rebreather/s: Other SCR Other Rebreather/s: Other SCR Join Date: Apr 2006 Location: Sweden & Florida Posts: 13	Re: Very deep dives inflation gas choice - risk of skin bends for Rebreather dives Quote: (Originally Posted by Drmike) If the inside of the suit is at ambient why would the underwear CLO value decrease? There is a pressure differential inside the suit since the gas want to rise. For instance when you are riding a scooter your hand and arm are more squezed. Also a difference beteen breast and back. Small but enough to make a difference. There are some tests on 3Ms thinsulate where they tested it at different pressures and got different CLOs. I don't know however if the fibers themselves are subject to any compression depending on the absolute pressure. Peter
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4th May 2006, 17:15	#23 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,157	Re: Very deep dives inflation gas choice - risk of skin bends for Rebreather dives Quote: (Originally Posted by Peter Steinhoff) There is a pressure differential inside the suit since the gas want to rise. For instance when you are riding a scooter your hand and arm are more squezed. Also a difference beteen breast and back. Small but enough to make a difference. There are some tests on 3Ms thinsulate where they tested it at different pressures and got different CLOs. I don't know however if the fibers themselves are subject to any compression depending on the absolute pressure. Peter Surely you would have the same difference between chest and back at any depth for the same amount of comfortable squeeze? Put a piece of undergarment into a sealed container and pressurise it. Why would its COL value change? For it to change the material must be crushed. To do that a differential would have to exist the deeper you go. But in reality the diver controls the degree of inflation (differential) in his suit to what is comfortable at all depths. So I cant see how that can be. For the undergarment to crush more at depth the suit would need to crush more and so the diver would be in more pain...which he isnt...because he removes the differential (squeeze) by adding inflation gas. I can see that it is different with a wetsuit where the air bubbles in the neoprene are crushed - but thats only beacuse the diver cant make up for that by adding more air into the neoprene air bubbles the way he can add air into a suit to get rid of the squeeze ....its a quiet night __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
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4th May 2006, 20:02	#24 (permalink)
Peter Steinhoff New Member Current Rebreather/s: Other SCR Other Rebreather/s: Other SCR Join Date: Apr 2006 Location: Sweden & Florida Posts: 13	Re: Very deep dives inflation gas choice - risk of skin bends for Rebreather dives Quote: (Originally Posted by Drmike) Surely you would have the same difference between chest and back at any depth for the same amount of comfortable squeeze? Put a piece of undergarment into a sealed container and pressurise it. Why would its COL value change? For it to change the material must be crushed. To do that a differential would have to exist the deeper you go. But in reality the diver controls the degree of inflation (differential) in his suit to what is comfortable at all depths. So I cant see how that can be. For the undergarment to crush more at depth the suit would need to crush more and so the diver would be in more pain...which he isnt...because he removes the differential (squeeze) by adding inflation gas. I can see that it is different with a wetsuit where the air bubbles in the neoprene are crushed - but thats only beacuse the diver cant make up for that by adding more air into the neoprene air bubbles the way he can add air into a suit to get rid of the squeeze ....its a quiet night Mike, I don't know and neither do you, and that is my point. You are just guessing... Maybe a large portion of the small thinsulate fibers are welded shut during manufacturing and act as pressure containers. Regarding the pressure maybe I should have used the word compression as if you press it together. When the fibers are more compressed, which they are on some body parts compared to other, their thermal characteristics change because the fibers are closer to each other. Also diving an Rebreather compared to OC would be different because you don't have the same cooling effect (increasing with increasing depth) from the breathing gas. That means you now loose a larger proportion of your heat from your body. And then at depth we also have the effects of increased CO2 production (gas density) and nitrogen narcosis that could change our bodies thermal response. There are simply too many factors to draw the general conclusion that argon would not make a measurable difference to air in all diving scenarios. If we only look at the gases physical properties argon IS a better insulator than air. Would love to continue this discussion but I got take off for 2 weeks of intense cave diving. Regards, Peter
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5th May 2006, 00:52	#25 (permalink)
dteubner Pedant Current Rebreather/s: Sport Kiss Classic Kiss Other Rebreather/s: Join Date: Mar 2005 Location: Adelaide, Australia Posts: 216	Re: Very deep dives inflation gas choice - risk of skin bends for Rebreather dives Quote: (Originally Posted by Peter Steinhoff) Simon, First of all I would imagine everyone being in agreement that gas properties do make a difference? Everyone in doubt are free to conduct a dive with a high helium gasmix as a drysuit inflation gas and tell us your empirical findings. Peter The diffence in conductivity of helium and air is over 6 fold, between air and argon about 1.3 fold. It's hardly the same thing. It's all about levels of evidence isn't it. Anecdotal evidence - "this thing that I have spent time and money and effort on makes me feel warmer" Theoretical evidence - "There is a small difference in a parameter that should make a difference to how warm I feel" Scientific evidnece - "An extremely well designed and conducted study showed no differrence" But the scientific evidence is in conflict with the anecdotal evidence - therefore the scientific evidence must be wrong. Flawed study design maybe? Dave T
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5th May 2006, 03:13	#26 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,157	Re: Very deep dives inflation gas choice - risk of skin bends for Rebreather dives Quote: (Originally Posted by Peter Steinhoff) Mike, I don't know and neither do you, and that is my point. You are just guessing... Maybe a large portion of the small thinsulate fibers are welded shut during manufacturing and act as pressure containers. Regarding the pressure maybe I should have used the word compression as if you press it together. When the fibers are more compressed, which they are on some body parts compared to other, their thermal characteristics change because the fibers are closer to each other. Also diving an Rebreather compared to OC would be different because you don't have the same cooling effect (increasing with increasing depth) from the breathing gas. That means you now loose a larger proportion of your heat from your body. And then at depth we also have the effects of increased CO2 production (gas density) and nitrogen narcosis that could change our bodies thermal response. There are simply too many factors to draw the general conclusion that argon would not make a measurable difference to air in all diving scenarios. If we only look at the gases physical properties argon IS a better insulator than air. Would love to continue this discussion but I got take off for 2 weeks of intense cave diving. Regards, Peter Actually I do know, and wasnt guessing - I was just being polite. Have fun with your intense cave diving. I will be doing a bit of cave exploration myself from end of next week. nothing too intense __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment Last edited by Drmike : 5th May 2006 at 03:22.
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5th May 2006, 05:24	#27 (permalink)
steevke Custom Title Allowed! Current Rebreather/s: Inspiration Vision Other Rebreather/s: Sport Kiss Join Date: Jul 2005 Location: Belgium Posts: 310	Re: Very deep dives inflation gas choice - risk of skin bends for Rebreather dives Quote: (Originally Posted by dteubner) The diffence in conductivity of helium and air is over 6 fold, between air and argon about 1.3 fold. And this 1.30 factor is for STILL and DRY air compared to argon. In reality, when diving the gas in your drysuit will not be still nor completely dry, so the theoretical 1.30 advantage is likely to be much LOWER in reality. Steven
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23rd November 2006, 23:01	#28 (permalink)
Sponge-Bob New Member Current Rebreather/s: Inspiration Classic Other CCR Dolphin Ray Other Rebreather/s: Other CCR Dolphin Ray Join Date: Nov 2006 Location: Scotland Posts: 29	Re: Very deep dives inflation gas choice - risk of skin bends for Rebreather dives Hi, I've used Argon and Air for suit inflation on extremely deep dives. Personally I think Argon is probably a placebo. I always found a suit heater works better! Personally I always opt for Air and have never had problems. Just don't even think of using your bottom mix My policy also is don't carry anything that can't be breathed, but then again air at 200m isn't goint to do you much good anyway! But I make sure that my suit inflation can be crosspatched into everything just in case I ever need it. But hey, don't trust me. Go with the science! Your a test pilot at those depths anyway. Stay safe... __________________ If you want a Guarantee.....Buy a toaster!
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24th November 2006, 04:42	#29 (permalink)
graham_hk New Member Current Rebreather/s: RB80 / Clone Other Rebreather/s: Inspiration Classic Classic Kiss MK 15.X RB80 / Clone Join Date: Nov 2005 Location: Philippines Posts: 88	Re: Very deep dives inflation gas choice - risk of skin bends for Rebreather dives Quote: (Originally Posted by steevke) And this 1.30 factor is for STILL and DRY air compared to argon. In reality, when diving the gas in your drysuit will not be still nor completely dry, so the theoretical 1.30 advantage is likely to be much LOWER in reality. Steven True but then the value for Argon is for still and dry and therefore when it is your suit it will increase just like air will so you would still have the 30% increase. Whether it makes a difference - well you'll have to make your own mind up Graham
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