Another SCUBA question

[Alpo]

In the book, these park rangers are doing a body recovery from one of the deeper divable wrecks in Lake Superior - the Kamloops.

 

I understand how heliox can prevent nitrogen narcosis. No nitrogen in the mix. But why would it increase the chance of hypothermia?

 

 

"Once again Ralph checked the gear. They were diving with air. Some divers used
roll-your-own heliox on Kamloops dives. Mixing gases was fundamentally risky
business and the National Park Service stayed with air. The mixture of helium
and oxygen eliminated the effects of nitrogen narcosis but compounded the
effects of hypothermia."

[Abilene Slim SASS 81783]

The short answer is due to their molecular makeup, helium transfers heat more readily than nitrogen. 
 

I know that doesn’t really help answer your question. I just know that from diving training many years ago. I never used mix gases because at the time it was too dangerous for all but expert commercial divers. 

[Alpo]

I believe it does answer it.

 

If helium transfers heat more readily than nitrogen, then helium in the lungs would take more heat from the body than nitrogen would. So you are exhaling your body heat faster breathing heliox then you do when breathing air.

 

I think.

[Sedalia Dave]

Thanks Abilene Slim I learned something today.

 

Disadvantages of helium in the mix

 

Helium conducts heat six times faster than air, so helium-breathing divers often carry a separate supply of a different gas to inflate drysuits. This is to avoid the risk of hypothermia caused by using helium as inflator gas. Argon, carried in a small, separate tank connected only to the inflator of the drysuit, is preferred to air, since air conducts heat 50% faster than argon.[6] Dry suits (if used together with a buoyancy compensator) still require a minimum of inflation to avoid "squeezing", i.e. damage to skin caused by pressurizing dry suit folds.

[Alpo]

I didn't know you inflated dry suits.

[DeaconKC]

In honor of this thread...

https://www.thejump.net/humor/jellyfish-bad-day.htm

[Red Gauntlet , SASS 60619]

My dad was a serious SCUBA diver in the early days of the sport on Puget Sound. He took me snorkeling once in a wetsuit in the Tacoma Narrows to see if I'd like to dive. Wetsuit or not, that water is....cold, cold. A couple of my brothers took to the sport, but not me...

[Ozark Shark]

1 hour ago, Alpo said:

I didn't know you inflated dry suits.

Yep.  Since they're sealed, the diver has to equalize pressure to avoid the squeeze described which means you have to manage the gas as you change depths.  A dry suit typically adds to your buoyancy requiring additional dive weight.   And it can impact your normal swimming trim angle which can be corrected with trim weights.

[Utah Bob #35998]

53 minutes ago, Red Gauntlet , SASS 60619 said:

My dad was a serious SCUBA diver in the early days of the sport on Puget Sound. He took me snorkeling once in a wetsuit in the Tacoma Narrows to see if I'd like to dive. Wetsuit or not, that water is....cold, cold. A couple of my brothers took to the sport, but not me...

A wetsuit does not keep you warm. It keeps you a little less cold.

[Red Gauntlet , SASS 60619]

So I learned!

[Ozark Shark]

1 hour ago, DeaconKC said:

In honor of this thread...

https://www.thejump.net/humor/jellyfish-bad-day.htm

On a dive trip in Roatan, I met a commercial diver from New Jersey who was rec diving with his family for the week.  At the bar we got into a discussion about the weird places he worked.  Besides the typical underwater construction (like diving inside a 100' deep 3' diameter tube to repair a weld at the bottom or bridge pier work), his company did a lot of sewer plant maintenance and repair work.  Given the environment, the diver wore a completely sealed system with surface air fed into the system via hoses.  So the diver could move freely around the tank, it required someone on the surface to handle hoses.  He said he always got a laugh out of the newbies being assigned to do the job with him.  He would offer to let them do the dive and they always turned it down thinking about what they were swimming in while not considering what manning the surface work met.  When he'd climb out of the tank at the end of the dive, there they would be covered in the muck from handling his air feeds.  To top it off, the hose handler also had to wash all that muck off the diver and clean the area.  By the time the diver could unseal his suit, he stepped out onto a freshly cleaned floor.  

[watab kid]

something wrong with diving in a sewer me thinks , 

[Parson Remington]

11 hours ago, Red Gauntlet , SASS 60619 said:

My dad was a serious SCUBA diver in the early days of the sport on Puget Sound. He took me snorkeling once in a wetsuit in the Tacoma Narrows to see if I'd like to dive. Wetsuit or not, that water is....cold, cold. A couple of my brothers took to the sport, but not me...

Back six decades, when I was but a lad, my grandparents had a home on the Kitsap Pennisula that fronted the Sound.  My cousins and I spent each summer there.  We would go swimming in the Sound; no wet suits, just clingy suits.  It was not warm, but we really did not care.

 

Year's later I got hooked on scuba and have dove throughout the Caribbean and South Pacific.  (Abilene Slim and Ozark Shark we need to compare notes;  Ozark Shark, did not know you were a diver, but your Alias makes more sense now.)  Somehow, somewhere in the intervening years I lost that tolerance of the cold.  I would no more dive in the Sound or along North American Pacific.  I even avoid now the strip mines I started diving in 40 years ago.