Trimix advantage for recreational diving below 130ft. Reference to literature wanted.

[walkonmars]

I'm not sure what information you are asking for.

I am one of a group that does not dive below 100 feet without helium. I use 25/25 for dives in the 100 to 130 range. I am way more clearheaded that way, and don't have the feeling of impending doom that often hits me around 100 feet on Nitrox, in our dark waters.

Helium's effect on decompression is controversial. Some schools believe that, because it is a fast diffusing gas, you need longer decompressions with it. Others believe that, because it is so poorly soluble, using the same schedules as Nitrox may even be more conservative than you need to be. I think everyone agrees that helium will come out of solution into bubbles easily if ascents are not controlled, so it is a unforgiving gas if you can't slow your ascent in the shallows.

I don't know of any "literature" on the use of helium in deeper recreational depths. I just know a lot of people who do it.

Thanks, for your patience.
You are answering some of my questions. I'm just trying to find out what advantages sport divers have in using trimix in the depths shallower than 130.
Do you get improved situational awareness even at 70-90ft? Is there research showing less physiological stress?
I'm told it is prohibitively expensive but if money is no object, is it better to use it (instead of nitrox) at sportdiver depths? (Assuming all safety procedures are followed)
Let's say you own a dive shop and can get unlimited trimix (and nitrox) any ratio you want for free. Would you use it to dive at 70 feet?
You are describing increase anxiety at 100. Do you feel any different at 70ft on trimix compared to air?

It is starting to sound like it isn't worth using trimix at shallow depths even if it was the same price as air.

Thanks,
T

 

[DevonDiver]

Do you get improved situational awareness even at 70-90ft? Is there research showing less physiological stress?

What your asking is a personal, not generic, question. Does YOUR situational awareness suffer at 70-90ft?

 

[SanDiegoSidemount]

What your asking is a personal, not generic, question. Does YOUR situational awareness suffer at 70-90ft?

Indeed. Isn't part of advancing as a tech diver figuring out what END works best for you personally?

 

[walkonmars]

What your asking is a personal, not generic, question. Does YOUR situational awareness suffer at 70-90ft?

I suspect it does get affected at around the 80-90ft range. As I mentioned, the onset is probably mild enough that a person won't know they are getting into that state. Since my memories of dives in the 90-100ft ranges are usually blurry memories, I suspect that I am without any profound external indication of being narced. An interesting experiment or question you experienced guys could answer is if you crossover from air to trimix in the 70 foot range, do any of you feel any different?
I suspect not many can answer that since trimix being expensive, you wait to crossover only when needed in the very deep range?
Interesting discussion out of my first post. Thanks for contributing.

 

[TSandM]

I had the interesting experience of doing two dives on 21/35 that didn't turn out as they were planned. On the first one, a wall was supposed to start at 100 feet and go down to 150; almost all the divers on the boat missed the wall, and we ended up doing a silt inspection dive at depths between 100 and 120. We found a LOT of stuff! I don't know if my head was clearer or not, because I simply don't go down there on Nitrox. But the second dive was the really interesting one -- max depth 70 feet, burning off the rest of the trimix. It seemed to me that I was having a much easier time finding animals, photographing, and keeping in touch with my buddy and on top of all my data. Based on that single experience, yes, if helium cost the same as Nitrox, I would dive 30/30 all the time in the recreational range.

 

[NAM001]

Unforutunately you can not. Why? The computer is tracking 2 gasses (assuming a nitrox computer), those being o2 ansd n2. for the n2 portion i would think it would be ok, because the n2 is behaving like like the computer expects it to.... IE 20/30 trimix the body and puter treats it ike the n2 is 50, and it is. The problem is on the o2 side of the house. Saying that you have 50%o2 because of using a 30/20 mix tells your puter youhave 50% o2. the o2bg wll go nuts if you can get 50% at all lin a nitrox puter. If you have a medical incident and they review the puter. You wil initially set into motion the wrong treatment. Plus from your nitrox course you know that 50% o2 has a mod of around 70-80 ft. So if youare going to dive trimix use the proper computer.

Hi folks,


Can I assume if I mix a 20% to 30% helium blend with 30% O2 and use standard nitrox tables and computer algorithms I can be OK?

Thanks for your kind help.

T

---------- Post added January 28th, 2014 at 11:52 AM ----------

All the free gas of any kind you want..... Then sure go for it. (with training) I am sure you will get all the benifits of reduced n2 as narcosis goes and also the benifits of reduced 02 issues. However for most of us trimix < 130 is not just cost prohibitive, the benifits per cost is just not there.. (Images of helios at 100 ft.) Another benifit of using helium is the gas weight issues. 2-3# per tank as opposed to 6-10 per tank.

Thanks, for your patience.
You are answering some of my questions. I'm just trying to find out what advantages sport divers have in using trimix in the depths shallower than 130.
Do you get improved situational awareness even at 70-90ft? Is there research showing less physiological stress?
I'm told it is prohibitively expensive but if money is no object, is it better to use it (instead of nitrox) at sportdiver depths? (Assuming all safety procedures are followed)
Let's say you own a dive shop and can get unlimited trimix (and nitrox) any ratio you want for free. Would you use it to dive at 70 feet?
You are describing increase anxiety at 100. Do you feel any different at 70ft on trimix compared to air?

It is starting to sound like it isn't worth using trimix at shallow depths even if it was the same price as air.

Thanks,
T

 

[kwinter]

To those who say that nitrox does not affect narcosis because O2 is as narcotic as nitrogen, I call BS. I don't consider O2 narcotic until at least 80 m/265 ft. But it is true that there has been no study that demonstrated less narcosis based on the reduced N2 content at recreation depths.

However, reaction to narcosis is a very personal thing and the OP seems to think there is some benefit to adding He on 90 foot dives. So I suggest a blind study since it would cost very little. Take 2 identical tanks. Fill one with EaNx 35 and the other with 35/6. Both gasses give pO2 of 1.4 at 100 feet. The trimix gives END of 66 feet. Without marking the tanks, use them on different dives to 100 feet and record your observations. That will give you some idea if the slight 6% helium makes any difference except in the cost and hassle of blending.


Please pardon any typos. Sent from my iPhone using Tapatalk

 

[DevonDiver]

To those who say that nitrox does not affect narcosis because O2 is as narcotic as nitrogen, I call BS. I don't consider O2 narcotic until at least 80 m/265 ft. But it is true that there has been no study that demonstrated less narcosis based on the reduced N2 content at recreation depths.

There are two sides to the debate.

The physiological theory, as I understand it, says that gas lipidity and metabolism of O2 should mean that oxygen was not, or at least substantially less, narcotic.

The practical research, testing subjects in hyperbaric conditions, shows no difference in narcosis between air and nitrox.

I teach for two agencies. One (PADI) says that oxygen is considered narcotic. The other (ANDI) say that it isn't. I guess it just depends whether you have an inclination to believe the theory (and assume tests were inconclusive) or vice-versa.

 

[OkByMe]

Hi folks,

Just wondering if you have any recent references or threads that detail advantages of using trimix for recreational diving below 130ft.
I'm not a tech-diver but only a nitrox diver and a home partial pressure blender of nitrox.
I am a small time welder and own numerous gas cylinders for work and hobbies so helium for me is readily available.
My motivations to home-blend nitrox was the convenience of not having to go to a shop 20 miles away. Driving 20 miles in traffic takes an hour each way on bad days from my home location.

I have read in some internet posts that diving with less nitrogen has no disadvantages for shallow depths. The details and quantitative examples are never posted at the location I see these claims.
One issue is the unforeseen narcosis effects. I don't recall ever being having narcosis even at wreck dives to 120ft. My worry is that I actually was "narced" because on those deep dives I have trouble recalling details I normally expect to remember. My guess is that a person gets improved situational awareness even at depths 80 and 90 feet.

I'm not asking to do tech diving without taking training. I just want to find out details of using Trimix at shallow depths (below 130 ft).
My expectation is that a person can take better speargun shots at fish, notice more lobsters and catch more details during a dive using trimix.
Can I assume if I mix a 20% to 30% helium blend with 30% O2 and use standard nitrox tables and computer algorithms I can be OK?

Thanks for your kind help.

T

http://www.envirodive.com/helium_blending.html
http://www.envirodive.com/helium_blending_2400.html
http://www.envirodive.com/helium_blending_3000.html
http://www.envirodive.com/helium_blending_3500.html
http://www.helium-scuba.com/Helium-SCUBA-Diving.html
http://www.helium-scuba.com/
http://www.divernet.com/other_diving_topics/tek_diving/160876/trimix_the_new_nitrox.html



Here is some reading for you. I bank 32% Nitrox and use the tables to fill Trimix. Since it usually costs me serveral hundred bucks to go to the gulf, I don't worry about the extra 20 bucks per tank for Helium. But I only use it deeper than 100'. A trimix computer takes the work out of planning the dive and compensates for variances to the plan. I use Galileo Sol with Trimix. 25/25/50 is about right for any gulf diving like the flower beds or the Oriskany. Never took a trimix course... I just figured it out. it just sounds harder than it is.

 

[walkonmars]

Bookmarked your links.
Thanks.