Recreational Trimix Course

[john j]

I liked some of Gramps' comments and they are in line with what I was trying to say earlier. I see the advantages of trimix for techinical diving like deep, extended, decompression dives, overhead environments, commercial dives, etc. I use a lot of trimix myself. I however, see no reason that a recreational, single tank, no-decompression diver needs trimix or truely benefits from it. Posters on this list have described the additional "safety" it would provide in that there would be less narcosis. This extra "safety" comes at the expense of additional hazards of using a mixed gas and the increased threat of DCS when blowing ascent rates or deco stops on helium mixes. If the diver accidentally goes into decompression, it's very inefficient decompressing on helium mixes. In essence you gain safety in one area by trading away safety in another. Net gain is nothing really. I don't think trimix has any business in the recreational single tank no-decompression dive arena. If you are talking decompression dives, or dives with extended bottom times that is completely different. If the recreational no-decompression diver needs extended bottom times or less narcosis, nitrox does the job just fine without the added complexity and cost of adding helium. Going to helium mix certification is a lot more complex and dangerous than going from air certification to nitrox.

[DRE]

Would you mind elaborating on this statement? Why is helium so inefficient to decompress from...

[Freedive WI]

John, What are you talking about? ???

Nitrox doesn't cause less narcosis than air. THat sounds like one of those old "wives tales" that came out when nitrox was first introduced. 02 acutally has a higher narcotic potential than nitrogen, but the fact that it get's metabolized cancels out any extra narcosis that the extra 02 adds to the mix.

Also, I have run some of the dive profiles on D-plan and the difference in 20 minute bottom times on nitrox versues triox is only 1 minute. How can 1 minute add that much extra time to the deco? If yourr talking about longer bottom times, we regularly do 45-50 minute bottom times on wreck surveys in the 120'-135' range on both nitrox and triox. Nitrox divers actually have longer deco than the triox divers- by only a minute or two, but it's still LONGER.

I have also seen more than one person narked at 100'. Most often this happens in cold water using a cheap regulator that can be over breathed. We both live in cold water states. Triox helps out wiht regs freezing, breathability AND narcosis. I have seen divers drift off to the point that we had to go grab them on cold water air/nitrox dives at 130'. When your the insructor in charge you want to have everyone as clear-headed as possible.

Bouyancy control should be a baisc prerequsite for any class. There was a time when you needed to have 100-125 dives to even start a technical class. THat's a lot compared to the 60 dives you need to become a scuba instrcutor. It's also a lot easier to control your bouyancy with a single tank on your back than it is with doubles and stages- something taken up later on in deco diving classes.

All of these arguments against triox sound just like the same old garbage we heard 10 years ago about nitrox:

" Why would I want to spend $10 on a nitrox fill when I can do the same dive on air for $5?

"Air is safe and nitrox is too advanced for the average recreational diver".

"THat's just a deep diving gas".

"Diver's will kill themselves with it"

Sorry, but nowdays nitrox is pretty wide speard all over the diving world. People have been diving helium around here since the 30's. Just because we had to jump through a lot of stupid hoops to get a trimix card ( 220' air dives in my extended range class) doesn't mean that everyone in the future should.

For those that think it's just an expensive gimmick that divers won't buy I say just look at split fins. Talk about something that's really overpriced junk and sells like "hot cakes". ???

If it was still just GUE pushing it I could why people would be bashing it, but since IANTD and TDI are now in the game I would think that it would get a bit more acceptance.

It's the future, along with rebreathers, and we are free to join in anytime we want. IF the cost is really too much than join Fred and I freediving. It can't get much cheaper than that.

Jon

[wtdrm]

Hi John:
Chuck Johnson here:
I am behind the curve here. I just started reading this thread. Dont know whether anybody will follow it or not. I saw your comments on "why" Rec Trimix. I will answer your question from my point of view.
You know me, I am older "52" Heavy (280 +) not in great shape and I smoke. Those are 4 great reasons to not mess with excess nitrogen ( deco). However I like to see the deeper shipwrecks also. Not the Kamloops or the Gunilda but the wrecks that are in my range. I have been on Ken's boat and we did the usual Deeper wrecks he goes to. According to my log book I dove them. I dont remember them, or much of them. Also according to my log books I have 45 dives beyond 80 feet. Now I can honestly say that I didnt feel narced on any of those dives. Why cant I remember much about the Congdon or the bow of the Emperor or the Chisholm engine? 3 weeks ago we dove Whitefish bay. The Vienna is at 120 ft. I cant remember much about this wreck either. The answer in my mind is, I was narced. I appreciate the fact that you have gone to a lot of time and expense in your training. I have seen you around the various dive sites and know you are a very knowlegeable, good diver. Not to mention an all around nice guy. I guess I will learn in the class the dangers of diving trimix. Then I will make the choice of diving that gas configuration. However I DO want to remember those dive I do beyond 80 ft. Therefore I think the new tec-rec class is a benefit and will take it. Besides, a good diver is always learning.
Just my thoughts.
CJ

[Inspirationdiver]

I think Chuck has a good point here. There is a significant narcosis level in the 130ft range. A lot of you out there who are doing deeper dives on air instead of trimix have become comfortable in the degree of narcosis that you experience. The thing you are forgetting is what it was like to go to 130ft before you had ever made any of those deeper dives. For those who don't have any intentions to make dives past 130, it would be nice to have a clear head while diving within those limits. I have been diving trimix exclusively this summer on all my dives up to depths of 270 ft. This past weekend I did a couple dives on air with my rebreather in Isle Royale to depths of 140 ft. I definately felt the effects of narcosis. I think this class has its merits, but it won't appeal to everyone. It really depends on what your long term goals are in diving.

[DRE]

If taught properly, this class should be about a lot more than just trying to avoid narcosis in the 130ft range. Let's face it, most people have already made up their mind whether they think they're subject to narcosis at that depth or not (the "my d**k is bigger than yours" syndrome)! However, the class should focus on doing proper ascent rates, when to use triox and when to use nitrox depending on the complexity of the dive, initiation to deco theory, etc. All of this is never covered in an "Advanced" OW - in this sense a well thought out triox course does bridge a gap between tech and rec diving, whether the student has any intention to ever dive to 300ft or not.

[WIdiver_Paul]

What Is Trimix?

Trimix is a combination of oxygen, helium and nitrogen. The idea behind trimix is to displace nitrogen with helium so that you can avoid the drawbacks of breathing high partial pressures of nitrogen.

Commercial divers omit nitrogen entirely for mid-range depths, using helium/oxygen mixtures called heliox. While certainly doable for tech divers, the logistics and costs are usually beyond most sport/tech divers capability.

For mixes in the deeper ranges, the required 02 content of your mix drops to the point that you can mix helium and air, called heliair, and not have to add 02.

To bring the advantages of replacing nitrogen with helium to every day sport/tech divers, it is advantageous to use partial pressure fills of oxygen and helium and then to top off with air.

The voodoo surrounding trimix

There is a misconception about trimix. Trimix is frequently promoted as the holy grail of scuba diving, so horrifyingly complex that you must take 4-8 levels of training before you can use it. In reality mixing a tank of trimix is no more complex than mixing a tank of nitrox.

What is complex and potentially dangerous is diving to extreme depths using multiple bottles of different mixes of gas, where choosing the wrong regulator can end your life in a hurry.

But it is possible to create a normoxic tank of trimix and treat it similar to air, without multiple mixes, bottles and other complexities, and enjoy the benefits of helium.

A fable about trimix is that you can't breath it on the surface. Generally speaking, the human body can handle lowered 02 percentages down to 16%. So, if you did a 17% mix, you can breath it as long as you want without fear of hypoxia. The breathability of a mix is solely dependant on it's 02 percentage, helium is complete inert and does not figure in.

Why use trimix?

The air we breath is composed of about 20.9% oxygen, 79.1% nitrogen and .033% carbon dioxide plus various inert trace gases. This is fine until we start breathing air under water. As we go deeper the partial pressures of these gases increase and we start suffering from their side effects.

Side effects of nitrogen include:

Narcosis- This is a mental function imparement which ranges from a mild euphoric feeling (60'-90'), slowing of mental activity (100'-130'), memory imparment and task fixation (140'-160') tingling in lips, legs and feet, severe drop in intellectual capacity (170'-200'), Voice reverberation, stupor and a sense of impending doom (200'+).

Bends- Nitrogen absorbed into tissues and fluids of the body reverting into gas bubbles.

Physiological- Damage to tissues leading to domino effects on immune system.

What about Nitrox?

Nitrox is an attempt to replace nitrogen with oxygen. Oxygen is metabolized by our bodies, so it is not absorbed into the tissue. Adding oxygen effectively reduces your nitrogen uptake, but there are some problems:

Side effects of oxygen include:

Central nervous system toxicity- CNS causes a seizure which can prove fatal while underwater. Partial pressures of over 1.6 can be extremely dangerous. 1.4 should be considered the maximum for a working dive, and it is reasonable to use 1.1 or 1.2 as your standard.

Inflammation of lung tissue from long term exposure- You can calculate your exposure to minimize this, but reports are coming in from the field of "lung burn out" caused by high levels of 02 which are well under the standard limits.

So why helium?

Helium is a non-toxic, colorless, odorless, tasteless, inert, lightweight and nonexplosive gas. To quote George Irvine head of the WKPP: "Helium is our friend".

Advantages of helium:

-Narcotic effects are nil.

-Due to its lower density, breathing resistance at depth is significantly reduced.

-Helium off-gasses rapidly and it does not enter slow tissues as readily as nitrogen.

Disadvantages of helium:

-Helium conducts heat 5 times faster than air.

-Hyperbaric arthralgia, an arthritic-like stiffness, can occur during descent with some divers.

Helium has been used for diving as far back as 1938. The first true test of heliox diving was the rescue of the submarine Squalus in 1939 in 240 fsw. Since then helium has been used in dives to more than 2000 fsw.

As helium is less dense than nitrogen, it enters and leaves the tissues faster than nitrogen. Paradoxically helium requires a little more decom time with short dives than air, but less decom time on long dives than air. The key to using helium is slow descents and slow ascents. Additional deep stops are required when ascending on helium mixes.

Due to helium's ability to leave tissues rapidly, having 2 or more stages, for example 50% nitrox and 100% O2, allows you to off-gas helium faster than you could nitrogen.

There is a situation which can occur in depths past 400ft. called High Pressure Neurological Syndrome (HPNS). This manifests itself with tremors, muscle twitching and coordination difficulties. Adding a small amount of nitrogen to your mix can alleviate these symptoms. But then, what are you doing down there, anyway?

Go ahead and use it!

Helium and diving were made for each other. You don't have to be a super tech diver to enjoy the benefits of helium. Breathing high partial pressures of Nitrogen is dangerous and hard on the body, so why do it? Replacing nitrogen with helium is a reasonable thing to do for single tank dives as shallow as 100'. What helium does for the 140-170 foot range (previously "deep air") is nothing short of miraculous. You remember the dive, you perform well under stress and you feel better after the dive.

[WIdiver_Paul]

Well, I gave up on the whole idea of recretional trimix course since there aren't instructors offering it, and the whole issue of fills once you have the rectmix card. I had a great experience working all the way throught the Advanced Trimix, but there seems to be an awful lot of repetition and redundancy in the curriculum. You learn the same PO2, mix and deco issues over and over in each class. I'm starting to think they should just make Nitrox/Advanced Nitrox/Deco/Extended Range/Trimix One class to certify you to 150' with extra dives for the deeper and Normoxic portion of the Trimix class. It would have to be like at least 10 dives but then again, I think i'd rather dive with someone that went the long route...

[Chuck_Northrup]

Paul,

I agree with you that the Recreational Trimix class is having difficulty finding its niche within the local community. I do not think that means that the class is without value

I think this class best fits after a recreational deep diver course and before Adv Eanx/Deco. I think if you are already certified through Adv Trimix this class would be overly redundant. You should already have the skills set, knowledge, and ability to obtain the mixes you want to dive in these 'shallower' depths. If you can not get the fills, then I guess that is a different story altogther. :-\

A Rec Trimix certified diver taking Adv Eanx/Deco can do the dives on mix, I think that is a big advantage to both the instructor and the student. Extended Range can be done away with (which it mostly is now anyway) and the student can then go straight to diving the deeper depths on mix. I am not suggesting that this student can cut out 'dives' but can cut out jumping through a few 'hoops'.

Just my .02 :