Will I ever dive deep on helium?

[roakey]

Originally posted by Liquid
I understand it is very problematic. There is also the issue of the bones deterioration dessise (can't remeber it's name) associated with saturation diving, that inflict a lot of comercial divers.

Dysbaric Ostionecrosis. I probably butchered the spelling. "Bone death by pressure" is how it roughly translates.

Originally posted by Liquid As for liquid breathing- I have a friend that his dream is to research this issue, and be the one to make the great break-through[/B]

Check out http://www.allp.com/LiquiVent/lv.htm for how they're already using breathable liquid to support premature babies breathing.

Roak

 

[mddolson]

This last summer I dove on trimix.
For the record, I'm a Nitrox instructor,O2 cleaning tech and certified gas blender and 1000 logged dives below 100 feet.
My personal narcosis limit on air is about 120 ft.
Below that I get paranoid, have difficulty multi-tasking, co-ordination and and feel some what drunk.

We dove the Empress of Ireland in September, depth :140 feet. Prior to this we has two training dives at Tobermory late July, on the Forrest City depth 145 feet.

We mixed Trimix 25/20 (25% O2, 20% He, 55% N2) NED (Narcotic equivelant depth on air is about 100 ft)
The helium cost $80 per bottle (enough to fill 4 sets of twin 98's)
We used argon gas in our dry suits.
Abyss Trimix decompression software was used to generate the dive tables and decompression profile.
We used 80 cuft aluminum stage bottles with EAN50, that we switched to at 65 feet during the ascent.


The benefits: safety, we were completely clear headed at depth, trimix easier to breath, less resistance.
Disadvantages: We needed argon for dry suits, helium is a good thermal conductor, and cold in a dry suit.Extra deco tank needed since Helium requires earlier (deeper) decompression and O2 cleaned regulators required for EAN50 deco gas. Need trimix tables or software. Cost: about $50 per fill compared to $30 for Nitrox .

Worth it: You bet your life it was!

Mike

 

[Ontario Diver]

In about 10 days I'm taking my Nirox/EAN course. I'm taking the course so that I'm aware and have the option of using a "simple" mixed gas. I am also aware of the pro's and con's of using it and when it makes sense to use it

Knowing where I want to dive and what diving I want to do, I will be diving trimix sometime. Not tomorrow, or the next day but some day.

In the meantime, thanks to all of you who keep talking about it so that I keep on learning.

 

[buff]

I am skeptical that the heliox pulls more heat from the body than air or nitrox.
I would think that diving that deep a diver always uses Heliox and not air or nitrox. The enormous volumes of air that are inhaled and exhaled ,at extreme depth, absorb a proportionaly huge amount of heat from the body(just look how much heat dogs can loose from panting-it's just like sweating but through the mouth).
It's the large minute volumes(how big of breath you take multiplied by how many you take per minute) and not the differnece between the gases that 's causing heat loss. I haven't looked it up in my physics book yet, but I don't think the heat capacitance of helium is that much greater than nitrogen or air-I don't know why it would be.
As for the expense of helium. There is only place around making Helium these days-the sun-and that's why it's so expensive.
I have dove a few times to 150' on air and have not had a problem-no buzz, no tingle, no euphoria. However, I dove with my wife to 130' and she could not figure which direction it was to back to shore. Nitrogen is just like anesthesia- it affects everyone differently.

 

[Lost Yooper]

Helium doesn't cool you by breathing it -- exactly. In fact, air will cool you more than helium mixes -- as far as the breathing gas is concerned. Basically, helium is cool when you breath it, but it doesn't draw heat out of you when you exhale. AIR does draw heat out of you when you exhale and thus cools your core body temperature.

Helium only cools you when you use it for dry suit inflation.

Mike

PS. The reference to HPNS (High Pressure Nervous Syndrome -- tremors, nausea, dizziness) in an earlier post is basically irrelevant until you hit about 400' and is individualized at that. HPNS can be, more or less, dealt with too.

 

[mddolson]

Buff, you wrote :The enormous volumes ofair that are inhaled and exhaled ,at extreme depth, absorb a proportionaly huge amount of heat from the body.

While respiration is a factor the biggest is noticed in your drysuit. As we descend the added gas injected into our drysuit to prevent squeeze and trim buoyancy (if Helium) is very conductive.

I experienced this first hand. Two dives, identical profile, depth and temperatures.
Max depth 145-148 feet, water temp 38°F.
On the secon dive I ran out of Argon (forgot to check it)at 100 feet(about 5 minutes into the dive). I switched to my backup wip,(on my back tanks Trimix 20/25)and continued. I was cold at the end of the dive. It was not until we got above the 30 ft deco stops that I felt some relief, surface temp was 70°F.

I was comfortable on the same dive profile the day before, when I used argon, suit gas for the entire dive.

These were longish dives in cold water, 25 minute bottom times, with 35 minutes of ascent.

Mike

 

[uwsince79]

Helium doesn't cool you by breathing it.

You have a fixed amount of volume in your lungs (small surface area) and when you breathe your body heats the gas to 98.6 degrees. That gas is trapped in you lungs while heated your body, under normal conditions heat loss is only about 10% of total heat generated by the body when breathing. The question then come to mind, how do you lose more heat if you are breathing He from tanks off your back that are close to the same temp as the surface without a increasing surface area? Unless you stick your tanks in a freezer for a week you can’t. As we use SCUBA the gas on our backs is usually at a temp much higher that that of commercial divers who are diving on a tether, and in the water a lot longer that us technical guys. They do have to combat this problem because highly compressed air traveling down a long tether will be cooled by the surrounding water so when you breath a gas mix that is lets say is now 37 degrees you will lose more body heat BECAUSE you body will warm it to 98 degrees from 37 for a longer period of time. This is when the gas draws more heat and (commercial divers you can help me on this to make sure I am correct) you would use a hot water suite & heated gas to combat both external and internal cooling . If memory serves me correct this comes into effect on depths deeper than 250 msw and the denser gas would play a roll on heat loss. This is not a problem with SCUBA, nor are many of you out there diving to 250+ msw, which is the depth where generated body heat is in equilibrium with the heat removed by cold breathing gas at the same temp of the surrounding water. (1.) We carry our gas with us under pressure, it is not pumped down to us and it is usually not that cold so our bodies do not have to heat the gas as much. Now Helium is always moving and even more so when it is heated so if your body is surrounded by it, as if it was used as a suit inflation gas these molecules would touch your body (a large surface area) heat and rise away from your skin cooling you. Like a constant breeze, removing the heat away from you over and over. So unless you in the Florida Keys and you need to cool off don’t use Helium in your Dry suit. I hope this post does not confuse anyone.

[ I can go into the actual physics of it if any one likes but I thought a layman’s explanation would be better. (It always works better for me).]

1.International Text Book Of Mixed Gas Diving, Theory Technique, Application
Heinz K.J. Lettnin, Best Publishing 1999 ISBN No. 0-941332-50-0

 

[DeepSeaDan]

uwsince79...

Outstanding! Your take on the commercial side of the issue is pretty accurate as well.

The following is copied from "Scubadoc's" website ( if you haven't be there yet....go...http://www.scuba-doc.com/ ....it is one of the best resources on the net for information on diving medicine, physiology & a host of other related topics):


COLDER BREATHING HELIUM?
There is much discussion whether you get colder breathing helium than breathing air. Helium has greater thermal conductivity than air. Undeniably, you lose more heat when surrounded by helium than by air, because heat conductance is the major factor in skin heat loss. Therefore helium is not used in dry suits. However, respiratory heat loss depends on heat capacity, and not at all on conductance. The thermal capacity of helium per gram is higher than that of air. However, there are fewer grams of helium for the same volume breathed because it is far less dense, making thermal capacity less compared to the same volume of air. Less heat would be lost breathing helium, so it should not chill you to breathe, as commonly thought. In a helmet or full face mask, your face may feel cool, making it hard to separate out the lesser loss through breathing.

Depth affects gas density, and so, heat loss through the breathing medium, and to be more confusing, you also need to account for interactions of respiratory heat loss through convection and evaporation. With helium you may also be more aware of the cold that is so common in diving, than when dulled by narcosis while breathing non-helium mixes. Remember too, it is generally not feasible to breathe air at depths where helium is used, so hard to compare in actual use. The short answer seems to be that breathing mixtures of helium at depths encountered by technical divers does not seem to result in greater cooling than breathing air. Helium feels colder to your skin than air, but it carries away less heat when you breathe it. So there.

 

[uwsince79]

Thanks for that link to scubadoc, nice site lots of great information. Great resource!

 

[omar]

You do not lose more heat breathing helium mixes when compared to air. In fact you will be transferring less energy into heating the helium breathing mix to body temperature than you would with air.

The heat capacity of helium is less than gaseous oxygen or nitrogen.
He is 20.786 J/K*mol
O2 is 29.4 J/K*mol
N2 is 29.12 J/K*mol

At standard conditions (STP) of 1 atmosphere and 25 degC. One mole of ANY gas will occupy 22.4 liters. ANY gas that has 1 mole of molecules has the same number of molecules (ie. 1 mole O2 = 1 mole N2 = 1 mole He).

So a mix of 20/40 which I use to 165 FSW will have 20% O2 by volume, 40% He and 40 N2 (we will ignore the trace gases). At the surface if I fill a balloon with this mix until it holds 22.4 liters it will have 0.2 moles of O2, 0.4 moles of He and 0.4 moles of N2.

The heat capacity will be (this is an approximation based on mole fractions):
(29.4 * 0.2) + (20.786 * 0.4) + (29.12 * 0.4) = 25.84
The same balloon filled with air will be:
(29.4 * 0.21) + (29.12 * 0.79) = 29.18

These ratios will not change with an increase in pressure. So at 165 the differences will be proportional. The difference of ~3.33 J is about 0.8 calories ( a tiny amount). 22.4 liters is roughly the amount of gas a typical male will breath at the surface in 2 minutes.

Thermo properties from:
R.H. Schumm, D.D. Wagman, S. Bailey, W.H. Evans, and V.B. Parker in National Bureau of Standards (USA) Technical Notes 270-1 to 270-8, 1973.