Heliox!

[MikeFerrara]

...I must differ with you on this one; here's a quote from N.O.A.A. on the subject, after a quick googling...


" One type of mixed gas diving involves the use of heliox. This (helium 79% and oxygen 21%) mixture is often used for very deep diving. Unlike nitrogen, helium is not known to have an intoxicating effect at any depth; it has a lower density than nitrogen, making it easier to breathe; and in cases of extended submersion, it improves decompression. Still, heliox has its drawbacks. It is expensive, has a limited availability, and its thermal conductivity is six times greater than that of nitrogen. This means that a diver breathing heliox will lose body heat six times faster than someone breathing compressed air or nitrox, making them susceptible to hypothermia. To prevent this, divers often wear special suits filled with hot water that is pumped down from the surface. Heating the heliox before the diver inhales it is another strategy used to combat hypothermia. Either of these procedures require specialized equipment and highly trained personnel."

...I can get you more, if you like.

Best,
Dano

What padiscubapro said. Anything we breath gets heated up but it takes less energy for us to heat helium than nitrogen. If breathing helium cooled us 6 times faster than air or nitrox a bunch of us would already be dead because we don't have heated suits or surface supplied warm gas...just an ice cold tank of mostly helium.

The NOAA should know better.

 

[DeepSeaDan]

What padiscubapro said. Anything we breath gets heated up but it takes less energy for us to heat helium than nitrogen. If breathing helium cooled us 6 times faster than air or nitrox a bunch of us would already be dead because we don't have heated suits or surface supplied warm gas...just an ice cold tank of mostly helium.

The NOAA should know better.

...this may be a difference of experience due to the greater depths / times / equipment involved in commercial gas diving; I don't pretend to know the physics of it all as well as you both do, but I do know that after years of sucking gobs of He. down a hose in all types of circumstances, using surface gas & saturation modes, that He. cools my willys more than air does.

Sometimes the best schooling is in the doing.

Best to ya's,
D.S.D.

 

[padiscubapro]

...this may be a difference of experience due to the greater depths / times / equipment involved in commercial gas diving; I don't pretend to know the physics of it all as well as you both do, but I do know that after years of sucking gobs of He. down a hose in all types of circumstances, using surface gas & saturation modes, that He. cools my willys more than air does.

Sometimes the best schooling is in the doing.

Best to ya's,
D.S.D.

Look at the reply just above.. In both the conditions you describe part of your body is SURROUNDED by helium (its not a "limited" breathing path).. This will cool you quicker, especially when the head is exposed to helium.. as most divers know most of your body heat is lost through the head..

there are two different mechanisms involved, breathing the gas VS losing heat through contact with a gas..

 

[DeepSeaDan]

Look at the reply just above.. In both the conditions you describe part of your body is SURROUNDED by helium (its not a "limited" breathing path).. This will cool you quicker, especially when the head is exposed to helium.. as most divers know most of your body heat is lost through the head..

there are two different mechanisms involved, breathing the gas VS losing heat through contact with a gas..

...is your infamiliarity with things deepsea ( no slight intended ).

My "head" is encased in a helmet with an insulating liner. In sat. tankage, my body is surrounded by an heo2 atmosphere that is conditioned for temperature & humidity, thus my willys are not chilly in there; out of the bell / in the water I'm bathed in hot h20 ( provided it doesn't crap out! ), thus I am comfortable as long as it's working. But put me in a dry bag on heo2 ( we switch at a pre-determined depth from air to gas ), & the rest of the dive is icy as compared to the time spent on air.

That is my experience ol' chap - if it doesn't jive with the textbook, well, the facts of my experiences remain a reality.

Regards,
D.S.D.

 

[padiscubapro]

...is your infamiliarity with things deepsea ( no slight intended ).

My "head" is encased in a helmet with an insulating liner. In sat. tankage, my body is surrounded by an heo2 atmosphere that is conditioned for temperature & humidity, thus my willys are not chilly in there; out of the bell / in the water I'm bathed in hot h20 ( provided it doesn't crap out! ), thus I am comfortable as long as it's working. But put me in a dry bag on heo2 ( we switch at a pre-determined depth from air to gas ), & the rest of the dive is icy as compared to the time spent on air.

That is my experience ol' chap - if it doesn't jive with the textbook, well, the facts of my experiences remain a reality.

Regards,
D.S.D.

unless your body is surrounded by 91.3 degrees f (average skin temperature) , the Helium will pull the temp away from your body quite faster than air so you need a higher temperature for the same confort level.. Just a few degrees difference will pulll body temperature away quite readily due to its high Thermal conductivity..

On OC scuba there is a very small gas path, that once heated is insulated by the body, so neither gas will give off the heat is absorbed until it exits the body, both gases should be reaching body temperature, its just that one reaches it faster consuming less calories..

Sitting at 70 degress in Air will be much more confortable than sitting at 70 degrees f F in heliox..

I know I do alot of 3+ hour dives on rebreathers in warm water with a wetsuit (cold water dives I dont count since I generally get cold pretty quickly both ways so a specifi time is hard to judge) .. around 80f I start to feel it about 3 hours when using a n2 based media, when I switch to a rich trimix (at least 50% he), I don;t feel the same until about 4 hours into a dive..

There is also one more IMPORTANT point to consider.. Respiratory Heat loss is proportional to pressure.. as pressure increases so does the heat loss.. So unless you compare the same gas at the same depth, comparisons are invalid..

if you read "life support systems and design" by nikols, sarich and tucker, they actually have a comparison for 100fsw, one using air and one using 83.2%He/16.8% o2..

Heat loss is given by Loss=a *rmv and Resp loss in watts = B*rmv

for air a= 115.b, b= 2028.8, for heliox a=101.3, b= 1780.1 - specified for 65%f and 20%rh

goto 200 fsw with tge same heliox mix and a=157.6 and b=2769.4

as you can see by just going an addtional 3 atas you have about a 56% additional loss of heat!

 

[DeepSeaDan]

unless your body is surrounded by 91.3 degrees f (average skin temperature) , the Helium will pull the temp away from your body quite faster than air so you need a higher temperature for the same confort level.. Just a few degrees difference will pulll body temperature away quite readily due to its high Thermal conductivity..

On OC scuba there is a very small gas path, that once heated is insulated by the body, so neither gas will give off the heat is absorbed until it exits the body, both gases should be reaching body temperature, its just that one reaches it faster consuming less calories..

Sitting at 70 degress in Air will be much more confortable than sitting at 70 degrees f F in heliox..

I know I do alot of 3+ hour dives on rebreathers in warm water with a wetsuit (cold water dives I dont count since I generally get cold pretty quickly both ways so a specifi time is hard to judge) .. around 80f I start to feel it about 3 hours when using a n2 based media, when I switch to a rich trimix (at least 50% he), I don;t feel the same until about 4 hours into a dive..

There is also one more IMPORTANT point to consider.. Respiratory Heat loss is proportional to pressure.. as pressure increases so does the heat loss.. So unless you compare the same gas at the same depth, comparisons are invalid..

if you read "life support systems and design" by nikols, sarich and tucker, they actually have a comparison for 100fsw, one using air and one using 83.2%He/16.8% o2..

Heat loss is given by Loss=a *rmv and Resp loss in watts = B*rmv

for air a= 115.b, b= 2028.8, for heliox a=101.3, b= 1780.1 - specified for 65%f and 20%rh

goto 200 fsw with tge same heliox mix and a=157.6 and b=2769.4

as you can see by just going an addtional 3 atas you have about a 56% additional loss of heat!

...ya got me! I can't argue with Nikols, Sarich & Tucker!

...Can we have a beer now?

D.S.D.

 

[MikeFerrara]

...ya got me! I can't argue with Nikols, Sarich & Tucker!

...Can we have a beer now?

D.S.D.

NO! I'm out.

 

[DeepSeaDan]

NO! I'm out.

go buy some, I can wait!

D.S.D.

 

[padiscubapro]

...ya got me! I can't argue with Nikols, Sarich & Tucker!

...Can we have a beer now?

D.S.D.

Sounds good to me.. I wasn't trying to be a smart*ss.

I knew your observations were from experience and what you reported is exactly why people think Heat loss is so great for BREATHING a Helium mix... But ineveitably the people forget to take into account pressure (and breathing rate)..

Surface and Saturation diving try to use the proper mixes for where they are diving/working, It would be foolish (and a huge waste of money) to use Heliox at a depth where air works fine...

for people following this thread...
"life support systems design" ISBN 0-536-59616-6 is a text used by the military and other groups.. Highly recommended reading!

M.L. Nukols PHD., PE - US Naval Academy Annapolis MD,
Ace J. Sarich, MSc, PE - Marine Acoustics Inc, Arlington Virginia
Wayne C Tucker, Ph.D. Naval Undersea Warefare Cebter - Newport RI

 

[DeepSeaDan]

Sounds good to me.. I wasn't trying to be a smart*ss.

I knew your observations were from experience and what you reported is exactly why people think Heat loss is so great for BREATHING a Helium mix... But ineveitably the people forget to take into account pressure (and breathing rate)..

Surface and Saturation diving try to use the proper mixes for where they are diving/working, It would be foolish (and a huge waste of money) to use Heliox at a depth where air works fine...

for people following this thread...
"life support systems design" ISBN 0-536-59616-6 is a text used by the military and other groups.. Highly recommended reading!

M.L. Nukols PHD., PE - US Naval Academy Annapolis MD,
Ace J. Sarich, MSc, PE - Marine Acoustics Inc, Arlington Virginia
Wayne C Tucker, Ph.D. Naval Undersea Warefare Cebter - Newport RI

...presentation of logic PSP! I'm afraid you've exposed my weakness for taking things at face value ( eg.: NOAA's take on heliox ); to be candid, it is all old news to me now, my deep diving years are mostly behind me ( though a few deep wrecks up my way have me toying with the idea of mixed gas scuba; but if I had my druthers, I'd want my helmet, hose & chamber back for such adventures! ).

...So, will that be a sit-down pilaver over 20 American beers, or 5 Molson Canadians ( same effect! )?

....Best of the season to you ( if you want to slip a copy of "Life Support Systems Design" into my stocking this year, I'll be most grateful! ).

Regards,
D.S.D.