why helium?

[miked]

A question from a "rec" diver:
What is the purpose of adding helium to breathing gas.
I'm assuming that the HE replaces some of the Nitrogen, but what does that accomplish.
Does Helium have properties that make it 'safer" DCS wise or ????


Thanks in advance.

Sorry if this has been addressed begore, I "searched"/tried to find a thread that answered this question, but I couldn't.

Mike

[wedivebc]

A question from a "rec" diver:
What is the purpose of adding helium to breathing gas.
I'm assuming that the HE replaces some of the Nitrogen, but what does that accomplish.
Does Helium have properties that make it 'safer" DCS wise or ????


Thanks in advance.

Sorry if this has been addressed begore, I "searched"/tried to find a thread that answered this question, but I couldn't.

Mike
Helium mainly offsets nitrogen narcosis which some people find unmanageble even at recreational depths. My personal experience is the narcosis is hardly noticable at those depths and the expense and added hassle does not warrant it. Also helium is a limited resource and as we have witnessed lately the cost will be coninuing to rise.
Of course there are those divers who like to brag they dive trimix and make the funny Donald Duck voice at the quarry.

[RonFrank]

I'm not Tech, but Helium prevents Narcosis.

I was watching a show where divers on the Andereia Dora where living in a Bell for extended diving, and they all sounded like Chip'N'Dale because they were constantly kept under pressure, and breathing Helium as part of the mix while in the Bell.

Too Funny! :rofl3:

[Meng_Tze]

You are right on track. He replaces a fraction of N2 and O2 (depending on mix type). This means less narcosis (O2 and N2) and less N2 uptake. Problem is that He on- and off gasses quicker. This generally means deeper short stops when ascending. There is far more to it, but at a high level this should cover it.

[Jimmer]

Hey Dave and Meng, a bit of a hi jack here, but do you guys use He at recreational depths with your rebreathers, since you're using less of it and it's more affordable, or do you switch out to air diluent for recreational depth dives?

[DA Aquamaster]

Technical divers will use Helium at depths where nitrogen narcosis is problematic. How much helium is added depends on the depth and the equivalent nitrogen depth - which divers usually try to limit to around 100'.

Consequently, the specific mix used depends on depth.

Some depth ranges and mixes are:
10'-100' = EAN32 or 30/30
110'-150' = 21/35 (21% O2, 35% He)
160'-200' = 18/45
210'-250' = 15/55
260'-400' = 10/70

Two things have to be considered when determining the bottom mix - the amount of helium (to keep the END around 100' to minimize narcosis and atthe same time helium cost), and the amount of oxygen (to keep the PPO2 under 1.4, or in some cases 1.2 to minimize decompression but also prevent oxygen toxicity).

For example if we are diving to 218 feet (the sand near the screws on the Oriskany), the standard mix of 15/55 would work with a PPO2 of 1.14 and an END of 79 feet. But the 15% O2 is below 16% and you'd need a travel gas to ensure you had adequate oxygen at shallow depths, especially if you are working hard swimming against a current.

Another option would be to use 18/45 which would have a PPO2 of 1.37 and an END of 105 ft. Some divers feel that a PPO2 of 1.4 or below is fine while others feel anything over 1.2 for a bottom gas is too agressive. Similarly, other divers feel an END of 100 should be a hard line, while others may feel the difference between an END of 100 and 105' is a moot issue and still others feel the END should be shallower at 60-70 ft. A third option would be to use a custom mix of 16/47 to produce a more conservative PPO2 of 1.22 and an END of 100'.

Another thing to consider is decompression. With DPlan for example with 30-85 gradient factors, a 25 minute dive at 218 ft on 18/45 would require 54 minutes of deco while 15/55 would require 60 minutes of deco for the same dive due to the lower O2 and higher He percentages in the mix and would cost more due to the higher He amounts. 16/47 would split the difference in deco at 56 minutes and in terms of cost - but is not quite as simple to aqcuire or blend.

Another area of controversy is decompression as some divers feel He mixes shoudl be used for deco such as 35/25 at the 120' stop while other divers may use 32% or 36% Nitrox instead at the same depths.

In general helium is a faster gas than nitorgen and saturates tissues faster but also off gasses faster so the deco profiles differ from air and most profiles with helium have slightly more deco and slightly deeper but shorter stop depths than air or nitrox and depth control is more critical to prevent bubble formation.

The standard mix mentioned above of 30/30 is designed for use above 100' and as such could be used by recreational divers trained in it's use. It result in an END of only 60' but frankly I think it is a massive waste of helium and it makes more sense to just do the dive on 30% or 32% Nitrox.

The helium we have on the planet was created by atomic decay over about a gazillion years, so even though He is the second most common element in the universe, it is a limited resource on earth - how limited is a matter of debate. What is not really debateable is that He prices continue to rise and will I suspect rise further to attempt to limit consumption. So open circuit trimix diving is probably going to become less common as more and more trimix divers transition to rebreathers where the He use is about 90% less than on open circuit.

[Bismark]

Helium mainly offsets nitrogen narcosis which some people find unmanageble even at recreational depths. My personal experience is the narcosis is hardly noticable at those depths and the expense and added hassle does not warrant it. Also helium is a limited resource and as we have witnessed lately the cost will be coninuing to rise.
Of course there are those divers who like to brag they dive trimix and make the funny Donald Duck voice at the quarry.

You are a trimix instructor and this is your answer? Ya' gotta be kidding me.

[wedivebc]

You are a trimix instructor and this is your answer? Ya' gotta be kidding me.
sorry, ya lost me.
Do you wish to contribute to this thread?

[wedivebc]

Hey Dave and Meng, a bit of a hi jack here, but do you guys use He at recreational depths with your rebreathers, since you're using less of it and it's more affordable, or do you switch out to air diluent for recreational depth dives?
Yes I do use He since I use very little of it so it's not like I am blowing $100 a dive when I do rec depths. I also feel rec trimix training is a waste of time. I do train people to use trimix for extending their range beyond recreational depths but I don't see the value for rec trimix.

[DA Aquamaster]

Wedivebc is on the money.

Many divers get way too hung up on a 100' END and a shallower END is just stupid and I suspect has more to do with the machismo of being a 'mix diver than anything else.

Personally, I think 150' on air or a suitable nitrox mix is preferrable to blowing $125-$150 for a fill of trimix unless the conditions are extremely demanding. Below 150 feet, trimix starts to make sense, but the number of dives you can afford to do there begins to drop in proportion to the cost of the gas. That, and the related need to go deep to be cool, creates a situation where a number of trimix divers do maybe less than a dozen dives per year and are far below their peak in terms of performance. They'd be better off doing a lot more dives in the 100-150 range on air to augment the few trimix dives they do per year.

[Bismark]

sorry, ya lost me.
Do you wish to contribute to this thread?

I believe you may have misinterpreted the OP's question. I don't believe he was referring to using HE in recreational limits but was questioning the use of HE in diving mixes in general. If you look at the experience of the OP I believe it would be a fair stretch to think they were interested in the rec/tech narcosis/HE debate. If I am indeed correct, then it would be safe to say that your answer was less than complete and that was what was surprising to me considering the information was coming from a trimix instructor.

In answer to your questions from the PM: Yes I am trimix trained, yes I regularly dive trimix, and yes I do dive trimix in the upper limits of the recreational range.

To the OP: there is a long standing debate regarding the use of Helium in depth ranges between 100-150'. The subject is one that will be sure to get heated quickly and many people maintain very strong opinions. You can easily Google this subject and spend the next month or so reading personal anecdotes ad nauseum. Good Luck and lay in a supply of gatorade.......

[wedivebc]

Good Luck and lay in a supply of gatorade.......
or kool-aid depending on which side of the debate you swing:D

[Bismark]

That was actually pretty funny so you must not be too narced.... I guess you must use enough HE in your Meg to keep your END set somewhere around 100' :D

[Meng_Tze]

Hey Dave and Meng, a bit of a hi jack here, but do you guys use He at recreational depths with your rebreathers, since you're using less of it and it's more affordable, or do you switch out to air diluent for recreational depth dives?

Rec CCR depths I do air dil.
On OC I do nitrox to about 35-38m. Then I start doing mix. But each to their own

[lamont]

Also helium is a limited resource and as we have witnessed lately the cost will be coninuing to rise.

at some point the price will get high enough that it'll be easy for oil and gas companies to make the argument that they need to invest in the necessary plant to capture helium instead of just bleeding it off, then the prices will come down.

[Bismark]

As for the view that people are willing to accept the higher risks of diving air at depth rather than pay for helium, I wonder if they would also prefer to use older parachutes with an increased likely hood of failure but at a cheaper cost rather than pay the extra costs for a new parachute rental or just stay home that day. The argument for choosing not to dive mix because it is too expensive is pretty silly really. You can always stay home. If I can't afford to rent a plane with seatbelts I won't go flying. :-)

[DA Aquamaster]

As for the view that people are willing to accept the higher risks of diving air at depth rather than pay for helium, I wonder if they would also prefer to use older parachutes with an increased likely hood of failure but at a cheaper cost rather than pay the extra costs for a new parachute rental or just stay home that day. The argument for choosing not to dive mix because it is too expensive is pretty silly really. You can always stay home. If I can't afford to rent a plane with seatbelts I won't go flying. :-)That analogy is patently misleading. Personally, I have never seen any difference in the rental cost of a new parachute versus and old one and if the old one is still certified, there is no significant difference in terms of reliability.

Of course if you get to the tech equivalent of skydiving, you will be packing your own primary chute (the reserve is rigger packed every 180 days by FAA reg) and will have by then probably invested the $4k-$5K for your own rig.

A better analogy is a skydiver who does 100 jumps per year because he owns his own stuff, packs his own chute and is paying only for his share of the jump plane and is consequently a lot better at relative work than the guy who rents and does maybe 10 jumps per year you perpetually stays at about the same level as a newby fresh off a static line.

In the water at 130-150 ft, I'd much rather have an experienced buddy with 50 plus deep air dives in the last year than a mix breathing buddy with 5 or 10 trimix dives in the last year. The difference in currency, experience and skill goes a long way toward offsetting the downside of not being on mix. The reverse is not true as trimix does not cure a lack of currency or experience any more than a new parachute will make an inexperienced skydiver better or safer.

In flying, skydiving or technical diving, if you cannot go often you need to seriously rethink whether you should be going at all.

[wedivebc]

As for the view that people are willing to accept the higher risks of diving air at depth rather than pay for helium, I wonder if they would also prefer to use older parachutes with an increased likely hood of failure but at a cheaper cost rather than pay the extra costs for a new parachute rental or just stay home that day. The argument for choosing not to dive mix because it is too expensive is pretty silly really. You can always stay home. If I can't afford to rent a plane with seatbelts I won't go flying. :-)
Your whole argument is based on the assumption that there is an increased risk. It is my belief that the risk is no greater diving to 130ft on air than diving the same on trimix. If you have any statistics to prove diving recreational depths is safer please provide them.
I agree some people are more succeptable to narcosis, mostly heavy breathers. I am not one of them so I don't see the risk at a personal level either.
I do believe diving trimix adds other risks that outweigh the narcosis potential which also factor into my opiion of this. So rather than look at just cost I am considering cost, risk, availablity, training requirements and requirment to carry offboard suit inflation as just some of the factors weighing my opiion that recreation depth trimix is a waste of time. As I have indicated above since I am already set up, trained and have helium in my shed I do use trimix to recreational depths in my rebreather. I just don't advocate trimix for the masses.

[Bismark]

The argument between deep air diving and using trimix has been beaten to death and I for one have zero interest in trying to convince those who have already made up their minds regarding this. Simply put, the preponderance of scientific evidence clearly shows that no one "adapts to", "learns to tolerate" or "becomes accustomed to" narcosis any more than you become "adapted" to the effects of alcohol. Impaired is impaired. Period.

Dave, I absolutely agree with you that that anyone using HE requires a significantly higher level of skill to use it safely. However, in the vast majority of cases this can be accomplished by training and learning and practising those requisite skills. Yes for me to it is a question of risk assessment but I want to start my problem solving and dealing with an emergency 100% in the game. Further, I believe it is incorrect to look at the HE/narcosis debate without also bringing mentioning the further benefits of easier WOB and less chance of C02 buildup which is a real killer. I am not telling you anything you don't already know here I am sure, but since their are no absolutes in how a particular person responds to these issues from day to day (cold, fatigue, illness, mental stress....etc) one day's air dive to 130' may not be anything like the next day's air dive to 130. In my version of risk benefit, I prepare for the worst and pretty much enjoy evrything else.


Aquamaster, If I read your argument correctly, you said that you would prefer to dive with in the 130-150' range with someone who has done it 50 plus times in the past year rather than with the trimix diver who has only done 5 or 10 dives in the last year. You are of course entitled to your opinion but I wouldn't dive with either of them anymore than I would get in the car with a drunk drive who had successfully negotiated our route home while intoxicated the last 50 or so times. For that matter I wouldn't drive down a dangerous winding road with someone who was either just new to driving or had not been driving for a long time.

Anyways, like I said earlier this subject has bean beaten to death so I am done here.

[shellbackdiver1]

at some point the price will get high enough that it'll be easy for oil and gas companies to make the argument that they need to invest in the necessary plant to capture helium instead of just bleeding it off, then the prices will come down.

I work for the one of the 2 largest special and bulk gas companies in the world. We got lots of gas divers need. We got lots of He. I checked our sell price price to 3 different groups of customers (small, med and large volume). Hasn't really changed in years. Not in sales so I dont know how dive shops are getting it.

[Mike Edmonston]

My price on HE actually went down when I switched to a new supplier. I was paying $98 per T, now I am paying $56 per T.

Shop around.

[Fotoz4FX]

There is not that much more to see below 150' unless you are interested in doing some recovery or deep wreck diving (more training, of course) and I agree with both DA and WeDive that mixing gases beyond Nitrox for anything less than a deep dive is ludicrous and wasteful of the limited resource - of course H is more available than He and off gassing is even faster but the blending is hairy at best (you're messing with the triangle of fire with this mix... your tank valving very well might become the ignition).

Nonetheless, it is interesting stuff. I'm not a tech diver, not a deep diver, not interested in pushing my tissue compartments or myoptics (I'm 57) but certainly am considering at least learning more about it (and this is the place - thanks for the lesson DA).

[JeffG]

There is not that much more to see below 150' unless you are interested in doing some recovery or deep wreck diving (more training, of course)
Unless of course you want to look at some types of sponges that just start at around that level.


Not much to see past XYZ...LOL

[Meng_Tze]

I agree Jeff. I always laugh when I read those comments........... how do you know where I dive and what I see? 150ft on a tropical reef has some things, 150ft in the US altantic coast has some nice wrecks, 150ft in certain caves is just the entrance...... and this is just the beginning.

[ianr33]

There is not that much more to see below 150'

I'm not a tech diver, not a deep diver



If you tried it you might find you are wrong ;)

[texdiveguy]

I have seen more than one interesting 'thing' below 150ft. on
dives....it's like going into the back room of an antique shop....all the real goodies are in the dark.

[Mike Edmonston]

I have seen more than one interesting 'thing' below 150ft. on
dives....it's like going into the back room of an antique shop....all the real goodies are in the dark.

TEX is LYING!!!!

There is nothing to see below 130 ft, NOTHING AT ALL!!!! Don't even think of going deeper. All the pretty stuff is above 130.

Helium is a myth. Leave it to the nutjobs that are crazy enough to go below 150 ft. Besides it costs too much, so don't buy it!

Now, if you'll excuse me, I have to go and find NEMO :D

[texdiveguy]

TEX is LYING!!!!

There is nothing to see below 130 ft, NOTHING AT ALL!!!! Don't even think of going deeper. All the pretty stuff is above 130.

Helium is a myth. Leave it to the nutjobs that are crazy enough to go below 150 ft. Besides it costs too much, so don't buy it!

Now, if you'll excuse me, I have to go and find NEMO :D

Dang I have been caught again..... :(


;)

[Bismark]

There is not that much more to see below 150' unless you are interested in doing some recovery or deep wreck diving (more training, of course) and I agree with both DA and WeDive that mixing gases beyond Nitrox for anything less than a deep dive is ludicrous and wasteful of the limited resource - of course H is more available than He and off gassing is even faster but the blending is hairy at best (you're messing with the triangle of fire with this mix... your tank valving very well might become the ignition).

Nonetheless, it is interesting stuff. I'm not a tech diver, not a deep diver, not interested in pushing my tissue compartments or myoptics (I'm 57) but certainly am considering at least learning more about it (and this is the place - thanks for the lesson DA).

Not much to see below 150'? Ludicrous? And from what are you basing your conclusions? Surely SB is not providing you all the information you need to make your assessment. If these decisions are based on your extensive tech and deep diving in various locales around the world, then I apologize in advance and I am all ears.... :popcorn:

[wedivebc]

The argument between deep air diving and using trimix has been beaten to death and I for one have zero interest in trying to convince those who have already made up their minds regarding this. Simply put, the preponderance of scientific evidence clearly shows that no one "adapts to", "learns to tolerate" or "becomes accustomed to" narcosis any more than you become "adapted" to the effects of alcohol. Impaired is impaired. Period.
.
I will not debate the merits of deep air because I think diving to depths beyond recreational limits on air is not smart. I also don't feel that there is a great tolerance to be aquired other than being better able to deal with intoxication which is no smarter than learning to drive a car after a 6-pack.
The point I am debating is the recent trend toward calling depths between 100-130ft "deep air". When I started tech diving deep air was the only way to go. Trimix was there but several levels of training higher than that which was going to get me to 180ft on air. I don't do those dives anymore because I know better but the concept that 100ft is too deep for air and that an END of 60ft should be desired just makes me laugh. Again I say there are those (usually CO2 retainers) who get narced early and maybe they should use trimix but I don't see the value from my experience.
Do you consider recreational depth < 130ft to be deep air?

[Meng_Tze]

....the concept that 100ft is too deep for air and that an END of 60ft should be desired... .....
I guess if one (or many) position this to be true, the next step is to fill the newly created 'need' for additional training with a set of new courses...... Everyone wins. The agencies sell more courses, the equipment manufacturers sell more equipment and the divers get to dive technical and have bragging rights. I guess this is why I see more and more 'mix divers' at 30m (max with an average of 22m) sites.

[Bismark]

[QUOTE=wedivebc;3429020]I will not debate the merits of deep air because I think diving to depths beyond recreational limits on air is not smart. I also don't feel that there is a great tolerance to be aquired other than being better able to deal with intoxication which is no smarter than learning to drive a car after a 6-pack.

Pretty safe to say we are definitely on the same page here. My understanding is that the decision to make 130' the "recreational limit" was a rather arbitrary decision and had nothing to do with narcosis. Moreover, one could make the same argument that choosing 100' as a max END is also an arbitrary decision. Is .08 or .06 blood alcohol content the limit beyond which we can operate safely? The current science pretty clearly shows that narcosis starts as soon as you enter the water and then it becomes a matter of how "much" narcosis we should tolerate. Personally, I have a zero tolerance for drinking and driving and apply the same conservative standard to my diving. Further, I think we could agree that 130' in our neck of the woods is sure not the same thing as 130' in say, anywhere in the caribbean. However the fact remains that physics is physics and the gas laws are what they are, regardless of whether we are in the Caribbean or the PNW. The only real difference becomes one of perception and this has nothing to do with the actual physics of the situation.

Again it all comes down to a personal risk analysis. My personal decision is not to push my END deeper than 100' and I chose to take the additional training necessary to develop the skills necessary to dive with trimix. I also chose to make the commitment to a regular training and fitness schedule to keep those perishable skills current. What other people do is absolutely up to them, but my choices were what they were. I guess you have to draw the line somewhere and 100' makes a nice round figure to calculate gas consumption based on ATA's, as well as simple gas strategies using nitrox on depths less than 4 ata's. Again, everyone is entitled to their opinion and I don't intend to try and convert anyone who choses to disagree with me. I have been on dives where the C02 build up became problematic as a result of fatigue, coupled with poor viz and current. This made for some uncomfortable diving in warm and sunny climates and at very close to 100'. Again, I will base my decisions on the latest science coupled with personal experience and I don't let economics play any part in those decisions. If I can't afford to dive mix for the dive I want to do, I won't do the dive. Pretty simple and not unlike my decision not to drive or get in the car with someone who has been drinking at all. Just a fairly conservative approach. If I can't afford the taxi home from the bar, I would walk or call someone, but just because I didn't have the cash for the taxi I still wouldn't drive. I just chose not to put myself in a situation where my only options are all poor decisions. Dave, like you, I have a military background and one which developed a very strong proclivity to details where if we screwed up, someone's faimily was getting a letter from the CO. I don't ever want my loved ones to get one of those letters.

As to your direct question as to whether I consider dives deeper than 130' to be deep air dives, for the reasons mentioned above, I am not familiar with a standard definition of "deep air" that everyone agrees on. However, more to the point, I do consider an END of 130' to be deeper than I or anyone else should use. Again, just my opinion and I chose 100' for my max END for the reasons above and not just because any particular agency pulled it out of the hat.

[lamont]

I guess if one (or many) position this to be true, the next step is to fill the newly created 'need' for additional training with a set of new courses...... Everyone wins. The agencies sell more courses, the equipment manufacturers sell more equipment and the divers get to dive technical and have bragging rights. I guess this is why I see more and more 'mix divers' at 30m (max with an average of 22m) sites.

if all the mix divers who are diving to 30m are doing it for the bragging rights, how do you explain divers on mix at 30m who have done 100m dives?

[Meng_Tze]

if all the mix divers who are diving to 30m are doing it for the bragging rights, how do you explain divers on mix at 30m who have done 100m dives?

I dunno, they are setting 'an example'? :D

[AndrewJD]

Sorry if this was already covered in the last half of the thread which I didn't bother to read...

Helium provides three benefits:

1. Offset Narcotic Gases such as N2 and O2. The most obvious and already covered.

2. Reduce gas density and work of breathing at depth which leads to overexertion and CO2 buildup. Not so obvious and probably more useful then number 1 as CO2 is much more narcotic then N2 and O2.

3. Better decompression characteristics.

a. Offset Nitrogen.

b. Yes it goes in and out faster but it is also less soluble. Imagine a glass of warm water. Dump sugar into it and the sugar dissolves. Dump sand into it and the sand doesn't dissolve. N2 = sugar. He = sand.

It has one huge downside. Cost.

Jonathan

[wedivebc]

b. Yes it goes in and out faster but it is also less soluble. Imagine a glass of warm water. Dump sugar into it and the sugar dissolves. Dump sand into it and the sand doesn't dissolve. N2 = sugar. He = sand.

It has one huge downside. Cost.

Jonathan
If it's less soluable what does it go in and out of?

[gcbryan]

If it's less soluable what does it go in and out of?

I guess it's human nature for a proponent of anything to take it one step too far.:D

[limeyx]

If it's less soluable what does it go in and out of?

Ah, mr contrary speaks :)

In theory it's less soluble in "you" (bones, fat, muscle, blood, tissue, brains)
so less will "dissolve" in the body -- where does it go ? I dunno, maybe it's a stretch but I'd say perhaps it gets exhaled ?

Less gas in the body in theory (all theory :) means less decompression. Faster to exit means (in theory) a faster ascent "could" have a greater chance of DCS, but smaller molecules "could" mean that any effects are less than good ol air.

I surely hope summer comes to Canada soon ....

[Kevrumbo]

Ah, mr contrary speaks :)

In theory it's less soluble in "you" (bones, fat, muscle, blood, tissue, brains)
so less will "dissolve" in the body -- where does it go ? I dunno, maybe it's a stretch but I'd say perhaps it gets exhaled ?

Less gas in the body in theory (all theory :) means less decompression. Faster to exit means (in theory) a faster ascent "could" have a greater chance of DCS, but smaller molecules "could" mean that any effects are less than good ol air.

I surely hope summer comes to Canada soon ....
Nick, read these excerpts from Bruce Wienke:
. . .The size of bubbles formed with various inert gases depends upon the amount of gas dissolved, and hence the solubilities. Higher gas solubilities promote bigger bubbles. . .

. . .Another positive penny about helium diving scores the minimum-bends depth (MBD), that is, the saturation depth on a mix from which immediate ascension to the surface precipitates decompression sickness (DCS). For helium mixes, the MBD is always greater than that for proportionate nitrogen mix. For instance, the MBD for air (80/20 nitrox) is 33fsw, while the MBD for 80/20 heliox is 38 fsw. This results from helium’s lesser solubility compared to nitrogen as it impacts deeper and longer diving. . .

. . .For short exposures (bounce and shallow), the faster diffusion rate of helium is more important in gas buildup than solubility, and shorter NDLs than nitrogen result. For long bottom times (deco and extended range), the lesser solubility of helium is a dominant factor in gas buildup, and helium outperforms nitrogen for staging. Thus, deep implies helium bottom and stage gas. Said another way, transient diving favors nitrogen while steady state diving favors helium as a breathing gas. . .

. . .On most counts, helium appears superior to nitrogen as a diving gas. Helium bubbles are smaller, helium diffuses in and out of tissue and blood faster, helium is less narcotic, divers feel better when they leave the water after diving on helium, and helium MBDs are greater than nitrogen MBDs. . .
From Bruce Wienke, Deep Stops and Deep Helium (http://www.tek-dive.com/portal/upload/deep.pdf)

See also Bruce Wienke (BRW) in SB:
http://www.scubaboard.com/forums/379457-post6.html
http://www.scubaboard.com/forums/427265-post4.html (Helium Wins On All Accounts)

Nick, the article above may help you understand where the NAUI Tech divers are coming from (especially in that current TDS thread:11:). . .

[gcbryan]

Nick, read these excerpts from Bruce Wienke:

From Bruce Wienke, Deep Stops and Deep Helium (http://www.tek-dive.com/portal/upload/deep.pdf)

See also Bruce Wienke (BRW) in SB:
http://www.scubaboard.com/forums/379457-post6.html
http://www.scubaboard.com/forums/427265-post4.html (Helium Wins On All Accounts)

Nick, the article above may help you understand where the NAUI Tech divers are coming from (especially in that current TDS thread:11:). . .

I just read those posts. Can someone explain the difference to me between ongassing and solubility? I thought ongassing involved diffussion/solubility of the biomass. Just trying to learn something here!

[wedivebc]

I just read those posts. Can someone explain the difference to me between ongassing and solubility? I thought ongassing involved diffussion/solubility of the biomass. Just trying to learn something here!
Yes ongassing is the dissolution of gasses in tissue and is therefore affected by the solubility of the gas. My understanding is the transport of gasses is by both perfusion (tranport directly from arterial blood supply) and diffusion (gas transported by contact with adjacent tissue with a higher gradient). I think most dissolved tissue (single phase) models are known as parallel model and consider perfusion as the transport medium. I am sure there are others but I know DCIEM tables consider both perfusion (blood into tissue) and diffusion (tissue into tissue).
Accoring to the chart here Henry's law - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Henry's_law) He is only slightly less soluble than N2 in water but we also know it is much less soluble in other tissues such as lipids. How this effects the human body I am still unsure but this oversimplification
b. Yes it goes in and out faster but it is also less soluble. Imagine a glass of warm water. Dump sugar into it and the sugar dissolves. Dump sand into it and the sand doesn't dissolve. N2 = sugar. He = sand.

is not an accurate analogy. In fact I am really bothered by the drones who chant "heluim can't hurt you, helium is your friend". I can assure you helium coming out of solution and forming bubbles can do as much if not more harm than N2 especially in recreational profiles where shorter time at depth means faster tissue is more likely involved.
The current trend is to teach new divers that in the event of an OOA emergency the surface is a viable option. Although when diving air we can often get away with this but with the faster nature of helium I am concerned the cavilier attitude toward helium is going to land someone in a wheelchair or worse.

[TSandM]

The current trend is to teach new divers that in the event of an OOA emergency the surface is a viable option. Although when diving air we can often get away with this but with the faster nature of helium I am concerned the cavilier attitude toward helium is going to land someone in a wheelchair or worse.

I am not aware of any class which certifies you to dive helium that doesn't spend significant time teaching problem solving underwater. I've taken two recreational helium classes, and I will say that BOTH of them spent 99% of their time like a tech class, handling failures and maintaining our equilibrium (literally and figuratively) under stress in midwater. So I don't think the teaching that new divers get is really pertinent to how people are going to behave or the skills they are going to have while diving helium.

[wedivebc]

I am not aware of any class which certifies you to dive helium that doesn't spend significant time teaching problem solving underwater. I've taken two recreational helium classes, and I will say that BOTH of them spent 99% of their time like a tech class, handling failures and maintaining our equilibrium (literally and figuratively) under stress in midwater. So I don't think the teaching that new divers get is really pertinent to how people are going to behave or the skills they are going to have while diving helium.
That may be. Why do we call it recreational trimix and some agencies also have advanced recreational trimix?
I think if we aren't diving completely redundant systems which allow problem solving independant of a either a buddy or the surface we have no business diving trimix. Am I correct that your rec trimix training standards allow single tank with no redundant gas other than a buddy?
I for one think this is irresponsible and is minimizing the dangers involved with a gas that is still not as well understood as nitrogen. I feel trimix diving and its inherent dangers is a whole order of magnitude more complex than diving air or nitrox and should not be treated casually. I realize you had very intensive training but as long as you are diving with a single tank you are trusting your life to a buddy who may or may not be there when you need them.

[TSandM]

I believe GUE's standards still permit taking Rec Triox in a single tank, but none of us did, nor do I intend to do any dives where I would use helium on a single tank. And GUE's Rec Triox standards presuppose you have passed Fundies, which implies a certain degree of stability in the water, tolerance for task loading, and dependable team skills.

[Bismark]

That may be. Why do we call it recreational trimix and some agencies also have advanced recreational trimix?
I think if we aren't diving completely redundant systems which allow problem solving independant of a either a buddy or the surface we have no business diving trimix. Am I correct that your rec trimix training standards allow single tank with no redundant gas other than a buddy?
I for one think this is irresponsible and is minimizing the dangers involved with a gas that is still not as well understood as nitrogen. I feel trimix diving and its inherent dangers is a whole order of magnitude more complex than diving air or nitrox and should not be treated casually. I realize you had very intensive training but as long as you are diving with a single tank you are trusting your life to a buddy who may or may not be there when you need them.

Wow, a lot of assumptions in this one paragraph.

First, I believe they refer to it as recreational trimix because depth limits for the class are the same as recreational diving limits (or less) meaning, 130'.

Second, I am guessing that your reference to "completely redundant systems" that you are referring to independent doubles. I can see this is going to be another argument but I am not sure how independent doubles or doubles with an isolation manifold make any difference in using trimix. Looks like we have another point of contention here.

While I am definitely not dismissing the fact that trimix diving can be more complicated than air or nitrox diving, it doesn't need to be. Absolutely the diver requires more education and definitely the diver requires more skill (particularly with ascent rates and deep stops) but at that point one can make the comparison between diving trimix today and diving nitrox 10-15 years ago. There are clearly other factors to consider when diving nitrox than diving air but divers as a community seem to have been able to incorporate them into training and education and the "devil gas" of 15 years ago is now looked upon quite differently. And in my opinion, this is also what should happen with Helium, albeit with tigher educational and training and skill standards. :-)

Finally, I have to take issue with your last comment about diving with a single tank and trusting your life to your buddy. Yowza, I don't know where to start with that one. I think you can probably guess my leanings in this so that entire point is a non event. I don't dive with buddies I don't trust and I don't dive with people with anything other than the same gas in their tanks (singles or doubles) as me. Yes I do trust my life to my buddies and they trust me with theirs. Problem solved.

[limeyx]

Nick, read these excerpts from Bruce Wienke:


Nick, the article above may help you understand where the NAUI Tech divers are coming from (especially in that current TDS thread:11:). . .

Thanks for the links Kevin. I honestly have no idea where most NAUI divers are coming from since their story seems to be

"Oh, we use 100% O2 instead of 50% to avoid ICD" then I say
"Oh, so you guys dont promote using 50% first then adding 100%"
and they reply "Oh no, we can definitely use 50% as long as we talk with our instrucor and 'understand the risks' " whatever that is supposed to mean. Too much complexity for me.

My comments in quotes on He, are what "some" people believe, and NAUI does seem to think less He is better for the short bottom times.

My view is different. I will use He whenever I can, and dive it with no penalty compared to air (except using deep stops) and I actually think He is easier to offgass than air mixes (or lower He mixes) and I'm far less worried about it than air.

I have no issue doing a 45 min dive at approx 80-90 feet average on 18/45 for instance, and having no ill effects. Obviously 1 data point does not make a trend, but ...

[limeyx]

Wow, a lot of assumptions in this one paragraph.

.......

Finally, I have to take issue with your last comment about diving with a single tank and trusting your life to your buddy. Yowza, I don't know where to start with that one. I think you can probably guess my leanings in this so that entire point is a non event. I don't dive with buddies I don't trust and I don't dive with people with anything other than the same gas in their tanks (singles or doubles) as me. Yes I do trust my life to my buddies and they trust me with theirs. Problem solved.

it's just a different way of thinking that comes out of the way things used to be, and the way they sadly probably still are in a lot of areas.

Yes, N2 may be "well understood" -- it's understood (by a lot of people) that it's not very good for you at high pressures when diving, and Helium has a lot of properties that make it much better as long as you have reasonable skills and treat it right.

I have no problem diving 30/30 or 25/25 the same way I'd dive nitrox honestly.

[Bismark]

Okay, so now I am replying to my own post..........:-) I thought I better expand a bit on the buddy thing Dave.

It appears to me that your presupposition (is that a word actually?) is that when you said "diving with a single tank you are trusting your life to a buddy who may or may not be there when you need them" is that problems that may be encountered underwater can be solved with a redundant gas supply. I would posit that while an OOG incident is indeed an emergency, it is far from the only thing that can go wrong. I think what most people are missing with the whole "super buddy" approach that certain approaches to diving ;-) advocate is that the extra brain power in solving problems present when you have one or even better two buddies with the same training and skill level helps solve any problem you may encounter that much more easily. This does include OOG obviously, but it is not limited to that. I know in my business world how valuable having someone of comparable background is to solving problems and it is no different underwater. One might argue "what if" and create any sort of scenario where you "lose" your buddy, but most of those scenarios are predicated on accepting certain conditions that I would not. In fact, it might be a useful exercise for anyone to come up with a situation (other than a true lightning strike) where this is not the case?? Finally, like I mentioned in my post above, diving HE, whether for any type of diving requires a higher standard of skills. As far as I know, these skills are prerequisites of the GUE rec triox course and for good reason. With the proper skill and knowlege base, diving trimix recreationally becomes a viable and practical alternative to air and nitrox. (please let's discount the economic factors to save us some more posts back and forth):-)

[wedivebc]

Wow, a lot of assumptions in this one paragraph.

First, I believe they refer to it as recreational trimix because depth limits for the class are the same as recreational diving limits (or less) meaning, 130'.

Second, I am guessing that your reference to "completely redundant systems" that you are referring to independent doubles. I can see this is going to be another argument but I am not sure how independent doubles or doubles with an isolation manifold make any difference in using trimix. Looks like we have another point of contention here.

.
Now who's assumptin'. I never said anything about independants.

[limeyx]

Now who's assumptin'. I never said anything about independants.

Well, manifolded doubles dont fit the criteria. I dont know enough about rebreathers but since those divers have to carry bailout gas, I am guessing they aren't "fully redundant" surface-supplied -- someone still has to change the T-bottle.

Maybe you could let us know what you were meaning ?

[Mike Edmonston]

Rebreathers and T bottles????

Uhhh... I'm confused....:confused:

Weren't we talking about Helium or something???

[Bismark]

Rebreathers and T bottles????

Uhhh... I'm confused....:confused:

Weren't we talking about Helium or something???

You might just have missed the last page of posts. BTW, your photo in your avatar looks suspiciously like a set of manifolded doubles..........:crafty:

[wedivebc]

Rebreathers and T bottles????

Uhhh... I'm confused....:confused:

Weren't we talking about Helium or something???
Well as is typical when debating belief sysems with the assimilated, as soon as they run out of valid arguments to support their position they obfuscate the argument with nonsense.:shakehead:

[grazie42]

Well, manifolded doubles dont fit the criteria. I dont know enough about rebreathers but since those divers have to carry bailout gas, I am guessing they aren't "fully redundant" surface-supplied -- someone still has to change the T-bottle.

Maybe you could let us know what you were meaning ?
Bailout is fully redundant from the RB since itīs (at least usually) comprised of completely separate OC-tanks and since you carry enough to end your dive on the bailout (while breathed OC)...some units have/are modified to connect off-board bailout but I donīt think anyone plans their bailout on the assumption that theyīll be able to...at least, from my newbie-perspective, thatīs a bad idea...

[Bismark]

[quote=wedivebc;3432466]
I think if we aren't diving completely redundant systems which allow problem solving independant of a either a buddy or the surface we have no business diving trimix. quote]


You still haven't answered Lymex's question. What do you mean? You are not trying to obfuscate here are you Dave:D. Are you or are you not referring to independent doubles?

As a further question, if you are an advocate of independent doubles, In the interests of furthering my knowledge, I would like if someone would take the time to explain to me the benifits of using them versus manifolded doubles. I am not trying to be a pain here but I truly would like to know. As you might guess, I don't dive with divers who use them so I would truly like the rationale behind them. You can PM me if you like so I don't hijack the thread. Now does this sound like someone who has been assimilated Dave?;) ( I am serious btw, not trying to make some kind of joke)

[Bismark]

Bailout is fully redundant from the RB since itīs (at least usually) comprised of completely separate OC-tanks and since you carry enough to end your dive on the bailout (while breathed OC)...some units have/are modified to connect off-board bailout but I donīt think anyone plans their bailout on the assumption that theyīll be able to...at least, from my newbie-perspective, thatīs a bad idea...


Okay, so now I have another question: I don't dive a CCR so please help me with this one. What do RB divers do for bailout gas for a dive to say, 200' with, say a deco of 35 minutes? Do you actually carry enough bailout gas for the ascent and the deco (different bail out gases?) assuming the **** hits the fan at the last minute of the dive?

[wedivebc]

[
You still haven't answered Lymex's question. What do you mean? You are not trying to obfuscate here are you Dave:D. Are you or are you not referring to independent doubles?

I am sorry, I thought redundant breathing system was commonly understood to mean either doubles other than a single outlet crossover bar or a single with adequate bailout tank. By my definition an RBS could be doubles, RB with bailout or a single tank with pony bottle. I guess most of you guys stay away from the solo diving forum so wouldn't know this:D

Bismark, I would gladly debate independant vs manifold issues but not on this thread. Care to start a new one I'll be there:popcorn:

[Charlie99]

I just read those posts. Can someone explain the difference to me between ongassing and solubility? I thought ongassing involved diffussion/solubility of the biomass. Just trying to learn something here!To put things into perspective, remember that the early responses in this thread were about the overriding reason for helium --- lower narcosis. Divers may quibble over whether the proper maximum Equivalent Narcotic Depth is 30m/100', or 40m/132', or 50m/165', but at some combinations of dive conditions and depth it is wise to use helium to have less narcosis.

Then the discussion got into the relative performance of N2 and He in decompression. The post and links by Kevrumbo are a pretty good summary of the relative advantages and disadvantages.

==========

As to your question on the difference between ongassing and solubility ........

all gases will be absorbed into the bodies tissues. For any particular combination of gas and tissue there is 1) a speed at which it ongasses/offgasses, and a 2) maximum volume (per ata) of gas that will be absorbed by the tissue.

Helium, being a lighter molecule, is absorbed about 3 times faster than N2 for any given tissue. OTOH, the solubility of helium is lower in most body tissues, so the total amount of gas absorbed when saturated is lower.

On long, deep dives the lower solubility of helium is the important factor. Dual phase decompression models (aka bubble models) such as VPM and RGBM estimate the free phase volume (fancy term for bubble volume) and set the decompression profile and times to keep the free phase volume on ascent below a certain limit. Since for the same deep/long profile the total starting volume of dissolved He on a trimix or heliox dive will be lower than the total starting volume of N2 for the same profile nitrox dive, a larger fraction of the dissolved helium is allowed to come out of solution into free phase.

OTOH, for a shorter, shallower dive the faster absorption of helium as compared to N2 means that helium requires a bit more decompression for those dives. Or to put it another way, NDLs will be shorter for helium than for nitrox. The crossover point between deep/long dives where helium has the advantage vs. short/shallow where nitrox has shorter deco and/or longer NDL is roughly at the depth-time combinations that are the air NDLs.

Of course, this means that in the depth-time areas where nitrox has an advantage, that you aren't doing much deco or total ascent time, and the slight disadvantage of helium on these dives doesn't really matter much ---- other than to generate arguments on Scubaboard. :D

[Bismark]

Charlie99 You are the Man! Most excellent precis. I might just have to print that out for future reference.

[JeffG]

Well as is typical when debating belief sysems with the assimilated, as soon as they run out of valid arguments to support their position they obfuscate the argument with nonsense.:shakehead:

We could just call you names then. ;)

[wedivebc]

Okay, so now I have another question: I don't dive a CCR so please help me with this one. What do RB divers do for bailout gas for a dive to say, 200' with, say a deco of 35 minutes? Do you actually carry enough bailout gas for the ascent and the deco (different bail out gases?) assuming the **** hits the fan at the last minute of the dive?
I carry 1.5 times estimated gas required to safely surface deco included. Others may do it differently.

[TSandM]

I understood Dave to mean manifolded doubles when he said "fully redundant system", since the two sides can be isolated.

The fact is that, helium or not, as you go deeper, it makes sense to lay on more resources -- More gas, more redundancy, more skills, more training, more experience. Helium may or may not be more unforgiving of inaccurate ascents, but the fact is that deep dives near the deco limits are not going to be forgiving of poorly executed ascents, no matter what you were breathing.

My personal approach is that rock bottom always needs to be observed, and the need for a fully redundant system is going to depend a little on dive conditions and expected hazards. In our cold, murky water, I don't do dives at the 100 foot level or below without my doubles. In Cozumel, I did 100 foot dives on a single HP 100. In both cases, I had trained buddies that I was extremely unlikely to lose. That's the non-negotiable piece of "equipment" :)

[Bismark]

I carry 1.5 times estimated gas required to safely surface deco included. Others may do it differently.

Do you carry multiple bailout gases? If so, would I be correct in assuming that for the dive I postulated that you would carry 02, something else :D, and a bottom gas/travel mix similar or the same to what you are breathing at 200? 3 different bottles? What would be your ascent/deco profile with bailout from 200' on whatever mix you would choose?

[JeffG]

Do you carry multiple bailout gases? If so, would I be correct in assuming that for the dive I postulated that you would carry 02, something else :D, and a bottom gas/travel mix similar or the same to what you are breathing at 200? 3 different bottles? What would be your ascent/deco profile with bailout from 200' on whatever mix you would choose?

The rebreather divers I have talked/dived with would have 1 bottle of bottom gas (to get them from the bottom to the first deco stop) and may have mulitple deco bottles in reserve. The types and quantity of bottles differ between RB users, but I do know of some RB divers that carry the same deco bottles as a GUE/DIR open circuit diver (for the same depth of dive).

[wedivebc]

Do you carry multiple bailout gases? If so, would I be correct in assuming that for the dive I postulated that you would carry 02, something else :D, and a bottom gas/travel mix similar or the same to what you are breathing at 200? 3 different bottles? What would be your ascent/deco profile with bailout from 200' on whatever mix you would choose?
I carry a bottom bailout, using a high PO2 for 200ft 21/35 would do fine then carry one or two deco mixes. I would not use O2 as my primary deco mix but would probably use 50% for the dive you described. I would use a profile generated my v-planner at +2 for ascent and revert to my HS explorer for bailout.
I could also use a team bailout plan in some circumstances since the deco gas would only get used if there was bailout requred.

[Bismark]

Do you have a plan for lost deco gas or lost bailout if diving with someone else on an RB? Do you insist that all those diving together (assuming all on RB's) carry the same bail out gas? What happens when the depth gets in the 240' plus range and you start needing a s**tload of gas for both deco and ascent?

[wedivebc]

Do you have a plan for lost deco gas or lost bailout if diving with someone else on an RB? Do you insist that all those diving together (assuming all on RB's) carry the same bail out gas? What happens when the depth gets in the 240' plus range and you start needing a s**tload of gas for both deco and ascent?
I deco on my rebreather so gas usually doesn't get touched until last dive in the series when I might do bailout drill.
All contingency plans are based on one major failure, either loss of RB, loss of bailout gas, loss of buddy and immediate dive enders. If I have to make contingency plans for multiple failures I would be too scared to get in the water. Too many permutations for me to consider.:11:

[Bismark]

Gotcha, but would you carry all the gas reserves you needed for bail out on a dive in the 240-300' range? Seems like a lot of bottles. Do RB divers as a rule insist that you run your RB's with the same pp02s and then carry the same deco gas or is it every RB'er for themselves? :-)

[wedivebc]

Gotcha, but would you carry all the gas reserves you needed for bail out on a dive in the 240-300' range? Seems like a lot of bottles. Do RB divers as a rule insist that you run your RB's with the same pp02s and then carry the same deco gas or is it every RB'er for themselves? :-)
I would carry all bottom gas, and share deco gas 1.5 times that required for team. Team bailout also allows for optimal deco gas mixes as well.

[Bismark]

Okay, so for a 20-30 minute dive to 200' where you have oodles of gas in OC, particularly if you carry a stage (which sounds like you are doing essentially) what is the advantage of a RB? Sounds like you are carrying the same amount of bailout gas as I would.

[wedivebc]

Okay, so for a 20-30 minute dive to 200' where you have oodles of gas in OC, particularly if you carry a stage (which sounds like you are doing essentially) what is the advantage of a RB? Sounds like you are carrying the same amount of bailout gas as I would.
For a 20-30 minute dive yes I am probably carrying the same bailout gas as you. For deeper dives probably less (if team bailout used)
I am also using about 3-4 cuft of helium and I am also gradually replacing trimix with oxygen as I ascend so I only have to worry about ICD issues with regard to my bailout where I might push it a little more than I would normally.
I am breathing warm moist gas that my body does not have to reheat on every breath and I am carrying less weight on my back when I am out of the water. Should I decide to alter my dive plan I still have the optimal mix for the revised plan (within bailout parameters) and I never have some DIRF wannabe come up and tell me how I should be confiured:mooner: unlike when I dove independant doubles and had some obviously DIR kid come up and tell me I was going to die. I was too interested in getting in the water to try to educate him but diving RB means never having to explain yourself.
For square profiles the deco advantage of CCR is minimal in fact sometimes a well thought out deco plan can benefit from OC deco but in most of the diving I do, shore, cave, multilevel the fixed setpoint will provide lots of deco benefits.

[wedivebc]

...double post

[bletso]

Okay, so now I have another question: I don't dive a CCR so please help me with this one. What do RB divers do for bailout gas for a dive to say, 200' with, say a deco of 35 minutes? Do you actually carry enough bailout gas for the ascent and the deco (different bail out gases?) assuming the **** hits the fan at the last minute of the dive?

Yes, most of us do. The real big advantage of the rebreather vis-a-vis longer deep dives is I can carry my whole weekend's worth of gas on my back. The deco stages are plumbed in as off board deco gas/es. The stages serve to purge the system with the deco mix and that is all, just a few breaths per dive.

If something goes awry at the end of the last dive, I can go OC and complete my deco obligations. Rebreathers are beautiful!!!!! It also cuts down on the cost of gas necessary to do the dives.

I dive trimix on most dives over 30 MFW. A 40 cf trimix will last me a couple of weekends easily.
Dale

[Kevrumbo]

. . .My view is different. I will use He whenever I can, and dive it with no penalty compared to air (except using deep stops) and I actually think He is easier to offgass than air mixes (or lower He mixes) and I'm far less worried about it than air. . .

I have no issue doing a 45 min dive at approx 80-90 feet average on 18/45 for instance, and having no ill effects. Obviously 1 data point does not make a trend, but ...

. . .I have no problem diving 30/30 or 25/25 the same way I'd dive nitrox honestly. . .
<snip>I can assure you helium coming out of solution and forming bubbles can do as much if not more harm than N2 especially in recreational profiles where shorter time at depth means faster tissue is more likely involved.
The current trend is to teach new divers that in the event of an OOA emergency the surface is a viable option. Although when diving air we can often get away with this but with the faster nature of helium I am concerned the cavilier attitude toward helium is going to land someone in a wheelchair or worse.
Dave and Nick, I would agree while adding one subtle caveat due to an incident I had a few years ago using 30/30 Triox on repetitive NDL dives on backgas only, using Ratio/Minimum Deco Rules: at the end of three dives of max depths 100'/30m, 60'/18/ and 40'/12m, with 90 to 120min SIT, I developed a case of the chokes. Obviously there was an overloading of my lungs as a bubble filter due to what I believe now was excess residual helium. Dives were nominal multi-level progressions, with no ascent spikes or bouncing buoyancy problems that I can recall. . .

Long story short --I now always take an AL40 of Oxygen on Triox Repetitive Dives, and breath it at the safety stop on the next-to-last or last dive of the day (haven't had any similar post-dive dyspnea/shortness-of-breath symptoms since). . .

[bletso]

The current trend is to teach new divers that in the event of an OOA emergency the surface is a viable option. Although when diving air we can often get away with this but with the faster nature of helium I am concerned the cavilier attitude toward helium is going to land someone in a wheelchair or worse.

Absolutely correct!! NO ONE should be diving helium with the surface option mentality. Whenever I dive helium, I always tote the O2. It is just part of my kit.

It (helium based diving) requires a much more knowledgeable, and disciplined personality. i.e. Cave and or technical

Dale

[DiveBandit]

Call me old school, but when I learned to dive in the 80's, diving to a P02 of 2.0 was not uncommon, and I know more than a few divers who dove hotter P02's than that. It was lowered to 1.4 over the years because they found it to be a safer overall P02 for the masses. I'm all for safety, so I'm not against using 1.4. However, I think this whole argument over deep air is a little inaccurate. To say that deep air diving in certain situations isn't a good idea would be accurate. To say it's simply a bad idea period is simply wrong. I dive 220' in a low flow cave on air often. There isn't anything crazy about it. I'm not sure I'd dive that deep on air if I was in open ocean with current, but in a low flow cave it works fine for me. I carry stage bottles for back-ups and I deco on 100% and I've never been bent, and I've never oxtox'd. Same goes for the 3 divers that dive that deep with me. Yes, I agree it's not for everyone, but when I hear these arguments that anything deeper than 130' on air is stupid, or unsmart, or crazy, Etc. It simply isn't 100% correct. I think you simply need to progressively dive to whatever depth you feel comfortable with. For me, I believe that my "oxtox on air" line in the sand probably sits somewhere below 230', but I personally don't feel comfortable going any deeper than 220' and thats just me. I'm certainly not trying to make a blanket statement that everybody can dive to 220', but I am saying that a blanket statement that anything past 130' on air is crazy is simply not accurate.

That said, I would add that at some point I would like to get trimix certified simply because where I want to dive and what I want to see are at depths that require a mix that has less than 21%. I also want to try heliox and normoxic first - not because I'm made of money, but so I can learn about diving helium and experience it. There's nothing wrong with that is there.

Ok, My fire suit is on - Flame away if you must. :D

EDIT: in case the question comes up. 220' is a turning point. We only spend a minute or two at most at that depth.

[Mike Edmonston]

EDIT: in case the question comes up. 220' is a turning point. We only spend a minute or two at most at that depth.

The kaliedoscope of colors must be amazing at that depth, you could always bring some "Iron Butterfly" on an MP3 player to get the full effect... :D

[Meng_Tze]

WOW that is 7.7 ata. Which is a PO2 of 1.61 and PN2 of 6. Not flaming , but that is a lot. Kudos if you can handle that. I know I can't.

[Bismark]

Call me old school, but when I learned to dive in the 80's, diving to a P02 of 2.0 was not uncommon, and I know more than a few divers who dove hotter P02's than that. It was lowered to 1.4 over the years because they found it to be a safer overall P02 for the masses. I'm all for safety, so I'm not against using 1.4. However, I think this whole argument over deep air is a little inaccurate. To say that deep air diving in certain situations isn't a good idea would be accurate. To say it's simply a bad idea period is simply wrong. I dive 220' in a low flow cave on air often. There isn't anything crazy about it. I'm not sure I'd dive that deep on air if I was in open ocean with current, but in a low flow cave it works fine for me. I carry stage bottles for back-ups and I deco on 100% and I've never been bent, and I've never oxtox'd. Same goes for the 3 divers that dive that deep with me. Yes, I agree it's not for everyone, but when I hear these arguments that anything deeper than 130' on air is stupid, or unsmart, or crazy, Etc. It simply isn't 100% correct. I think you simply need to progressively dive to whatever depth you feel comfortable with. For me, I believe that my "oxtox on air" line in the sand probably sits somewhere below 230', but I personally don't feel comfortable going any deeper than 220' and thats just me. I'm certainly not trying to make a blanket statement that everybody can dive to 220', but I am saying that a blanket statement that anything past 130' on air is crazy is simply not accurate.

That said, I would add that at some point I would like to get trimix certified simply because where I want to dive and what I want to see are at depths that require a mix that has less than 21%. I also want to try heliox and normoxic first - not because I'm made of money, but so I can learn about diving helium and experience it. There's nothing wrong with that is there.

Ok, My fire suit is on - Flame away if you must. :D

EDIT: in case the question comes up. 220' is a turning point. We only spend a minute or two at most at that depth.

For the sake of clarification, please answer for me the following questions:

1) At what point do you believe narcosis begins to affect your ability to make timely and correct decisions?
2)Do you think your ability to react to an emergency is impaired with narcosis or not?
3)How do you reconcile the accepted science regarding narcosis with your decisions?

I am truly interested in your rationale here. Of course your decisions are your own and I don't intend to change your mind because it is not my right to do so. However, I am trying to understand the mindset of those who share the same opinion you do
regarding this. Personally I believe your approach is no different from that made by my rugby buddies who feel "good enough to drive" after several (many several) drinks. How do you personally reconcile that comparison with what you chose to do.

Again, interested in your point of view. Not a flame. We can agree to disagree.

[limeyx]

Dave and Nick, I would agree while adding one subtle caveat due to an incident I had a few years ago using 30/30 Triox on repetitive NDL dives on backgas only, using Ratio/Minimum Deco Rules: at the end of three dives of max depths 100'/30m, 60'/18/ and 40'/12m, with 90 to 120min SIT, I developed a case of the chokes. Obviously there was an overloading of my lungs as a bubble filter due to what I believe now was excess residual helium. Dives were nominal multi-level progressions, with no ascent spikes or bouncing buoyancy problems that I can recall. . .

Long story short --I now always take an AL40 of Oxygen on Triox Repetitive Dives, and breath it at the safety stop on the next-to-last or last dive of the day (haven't had any similar post-dive dyspnea/shortness-of-breath symptoms since). . .

Interesting, definitely something to consider. I have not had that experience but I dont do a huge amount of helium no or min deco diving, just usually last dive of the day if we have some gas left, or first dive of the day if it's going to be a bit deeper than the others.

Do you have the profiles handy ?

[DiveBandit]

The kaliedoscope of colors must be amazing at that depth, you could always bring some "Iron Butterfly" on an MP3 player to get the full effect... :D

I'm still waiting for them to make an ipod case that'll go that deep.:crafty:

For the sake of clarification, please answer for me the following questions:

1) At what point do you believe narcosis begins to affect your ability to make timely and correct decisions?
2)Do you think your ability to react to an emergency is impaired with narcosis or not?
3)How do you reconcile the accepted science regarding narcosis with your decisions?

I am truly interested in your rationale here. Of course your decisions are your own and I don't intend to change your mind because it is not my right to do so. However, I am trying to understand the mindset of those who share the same opinion you do
regarding this. Personally I believe your approach is no different from that made by my rugby buddies who feel "good enough to drive" after several (many several) drinks. How do you personally reconcile that comparison with what you chose to do.

Again, interested in your point of view. Not a flame. We can agree to disagree.

If your asking honestly for informational purposes I'll tell you. Keep in mind this is just my experience. I can't speak for the other guys I dive with.

1. About 50% of the time I start to feel some effects at about 180'. I can definetly say I'm feeling it at 200' to 210'. Some times oddly enough, I don't feel them at all. Part of how we deal with narcosis is to make our dive plan non-negotiable. By that I mean that as a rule we have a nice dive down through the cave till the lead diver hits 220' then we turn - period. Not 221', no "I'm feelin gooooood - lets go just a few more feet", nothing, We turn at 220' end of story. Otherwise we plan for emergencies and practice skills until there 2nd nature in shallow water just like you should for shallow water diving. We also live by the "any diver can call the dive at any time for any reason" rule which has been used once.

2. Having done the PVC pipe drill at 100', 150', and 200', I can tell you that for me there is no time difference from 100' to 150' but my time gets a few seconds longer when going from 150' to 200' so there is impairment. I think the difference between driving drunk and cave diving at 220' on air is this. In a car at 75 Mph while impaired, you take a few seconds to react to something that demands a split second reaction which usually doesn't make for good endings. While cave diving you can and should take a second or two to think about whats going on if you have the peace of mind to stay calm.

3. Not sure how to answer this one. But I guess I reconcile my decision like this. I tech dive. Some times your 60 feet down and 3000 feet back, some times your 200 feet back and 220 feet down. The only way to avoid risk all together is not to dive. Otherwise we use progressive penetration. The first time I dove a cave to 220 feet was not the first time I dove that cave. As stated previously by others. We each decide how far we are willing to go and how much risk we are willing to take. As the saying goes, "A man has got to know his limits". I have self imposed limits i created for myself. I'm not prone to panic, I work well under pressure, and I'm very familiar via progressive diving, with the cave I do those deep dives in, so my chances of meeting Jesus on one of those dives are low enough for me to live with.:D

Hope that gives you some insite into us crazy deepair divers minds :eyebrow:

[Meng_Tze]

Narcosis,
What system is that you do these dives in?

[Mike Edmonston]

I work well under pressure, and I'm very familiar via progressive diving, with the cave I do those deep dives in, so my chances of meeting Jesus on one of those dives are low enough for me to live with.:D

Hope that gives you some insite into us crazy deepair divers minds :eyebrow:

Well, a couple things...

I understand the fact that you recognize the effects, and that you choose not to exceed YOUR IMPOSED limits. But your choices can have severe ramifications in the community, and in your family should an incident occur.

It won't take much for the state to close down Eagle's nest again, if a deep air diver gets in trouble and drowns. The argument would be made that the diver knew there was a better gas choice, but chose to dive air anyway. They would assume that we are renegade genX divers, with no regard for safety, and that we can't police our own ranks. Results, cave closed.

How about your Family, would they not want the best for you? Would they not wonder why you did not choose to dive a more appropriate gas that could have possibly given you the chance to survive? Their sorrow and grief would last for months or years. Is that really fair to them?

I will not tell you how and what to dive, I only ask that you think about the repercussions that your actions have, long after you're not here to explain them.

Not doing so is just being selfish...

Safe Diving

[DiveBandit]

EDIT:I was going to PM this, but decided against it.

I knew someone was gonna go there. So the spiral begins

Mike, come on now. I appreciate that you are very safety minded, I met you once at Scuba west when they were having a Diverite demo day. You seem like a great guy, but please don't lop me and the people I dive with into the same bucket you would place the 3 guys on single AL80's and "ink still wet" cavern cards I saw gearing up at the Nest 2 weeks ago. That very boxed (and very repeated) response should be reserved for newb's who don't know what they don't know. I don't consider my self to be a tech god, but I do know what I'm doing, and I do have some experience at it. As my sig says. Posturing and politics are counter productive. If we're going to go down this road with this discussion instead of having a good educational discussion about deep air and helium, I'm out.

Safe diving all.

[Meng_Tze]

....
It won't take much for the state to close down Eagle's nest again, if a deep air diver gets in trouble and drowns. The argument would be made that the diver knew there was a better gas choice, but chose to dive air anyway. They would assume that we are renegade genX divers, with no regard for safety, and that we can't police our own ranks. Results, cave closed.

My thinking exactly........ I don't much want to address the 'deep air' thing. That is up to each individual and they will have to think through that for who they leave behind. No different than any other diver.

[Bismark]

Narcosis, thanks for the candid reply. I was truly interested in your train of thought here and I have no intentions of bashing you for your choices. I personally made different choices with the evidence I had at hand but that is just my choice. You made yours and that is that. I would be interested in hearing how you see the same dives once you do them on trimix. From an anecdotal perspective, several people I know who used to dive deep air and then took trimix training have reported completely different experience. I have never dove 200' on air so I don't have that to personally compare it too. My decision was based on the view that I didn't need to drive really, really drunk to appreciate driving sober, but again, that was my own point of view. I understand that part of the problem is the fact that narcosis also impairs your memory so even if someone tried an "experiment" for their own knowledge, they might not remember it anyways.......

Again, thanks for sharing your personal opinions.

[DiveBandit]

Bismark - your welcome, I always enjoy learning new things, and relaying my experiences to others so they can learn or glean information from it.
The memory thing is interesting. I've never lost my memory. but myself and others will sometimes lose the finer details. For example, you might see a sign at depth and remember the sign, where it was, it's color and all, but even though it was only 3 sentences, and you know you read it, you can't remember everything it said. Other divers I know have no memory loss at all!?

I'm pretty sure thats what they mean when you read passages about divers that switched to trimix and just love the fact that they can actually remember the dive back on the surface.

Meng - I don't really know how fast or slow anybody would be to close the nest, but here's some wood for the fire. from a St. Pete times article in 2003.

Once Chassahowitzka Wildlife Mangement Area took control of Eagle's Nest, they saw no reason to continue prohibiting divers; especially considering that each fall they invite liability with hundreds of camouflaged hunters armed with rifles and shotguns. "These divers know the risk they're taking," said Wickrowski, a wildlife biologist.

[Mike Edmonston]

EDIT:I was going to PM this, but decided against it.

I knew someone was gonna go there. So the spiral begins

Mike, come on now. I appreciate that you are very safety minded, I met you once at Scuba west when they were having a Diverite demo day. You seem like a great guy, but please don't lop me and the people I dive with into the same bucket you would place the 3 guys on single AL80's and "ink still wet" cavern cards I saw gearing up at the Nest 2 weeks ago. That very boxed (and very repeated) response should be reserved for newb's who don't know what they don't know. I don't consider my self to be a tech god, but I do know what I'm doing, and I do have some experience at it. As my sig says. Posturing and politics are counter productive. If we're going to go down this road with this discussion instead of having a good educational discussion about deep air and helium, I'm out.

Safe diving all.

Hey bud,

If you read my post again, you'll see that nowhere do I question your abilities, nor am I telling you how to dive. It was more of a "Please be careful" post, due to some of the recent incidents in our community. I still firmly believe that there are better gas choices available, but I am not discounting deep air if that's all that is available. (Try and get Trimix in Equador...).

Personally I like to dive mix whenever I am below 120'. I just feel better after the dive. This is a personal choice.

Safe diving

[Bismark]

Bismark - your welcome, I always enjoy learning new things, and relaying my experiences to others so they can learn or glean information from it.
The memory thing is interesting. I've never lost my memory. but myself and others will sometimes lose the finer details. For example, you might see a sign at depth and remember the sign, where it was, it's color and all, but even though it was only 3 sentences, and you know you read it, you can't remember everything it said. Other divers I know have no memory loss at all!?

I'm pretty sure thats what they mean when you read passages about divers that switched to trimix and just love the fact that they can actually remember the dive back on the surface.

Meng - I don't really know how fast or slow anybody would be to close the nest, but here's some wood for the fire. from a St. Pete times article in 2003.

Once Chassahowitzka Wildlife Mangement Area took control of Eagle's Nest, they saw no reason to continue prohibiting divers; especially considering that each fall they invite liability with hundreds of camouflaged hunters armed with rifles and shotguns. "These divers know the risk they're taking," said Wickrowski, a wildlife biologist.


The funny thing about memory is you don't remember what you forgot:D

[DiveBandit]

Hey bud,

If you read my post again, you'll see that nowhere do I question your abilities, nor am I telling you how to dive. It was more of a "Please be careful" post, due to some of the recent incidents in our community. I still firmly believe that there are better gas choices available, but I am not discounting deep air if that's all that is available. (Try and get Trimix in Equador...).

Personally I like to dive mix whenever I am below 120'. I just feel better after the dive. This is a personal choice.

Safe diving
Then you have my apologies. See, I said you were a great guy:D

The funny thing about memory is you don't remember what you forgot:D

LOL, so true...

[Mike Edmonston]

Then you have my apologies. See, I said you were a great guy:D


No Problem,

By the way, if you're even in need of Trimix or a Normoxic class, give me a call. I'll dive with ya.. :D

Be safe

[limeyx]

My thinking exactly........ I don't much want to address the 'deep air' thing. That is up to each individual and they will have to think through that for who they leave behind. No different than any other diver.


Well, isn;t the main benefit of all that narcosis that you only need to dive a single site over & over again to get all the fun dives you need -- as you can never remember what you saw afterwards, you can just go to the quarry 50 times a year and pretend you went to different wrecks :)

[Kevrumbo]

Well, isn;t the main benefit of all that narcosis that you only need to dive a single site over & over again to get all the fun dives you need -- as you can never remember what you saw afterwards, you can just go to the quarry 50 times a year and pretend you went to different wrecks :)
Why do ya think I keep wanting to return to Truk Lagoon???:lotsalove:

[DiveBandit]

Kinda like the movie 50 first dates with Adam Sandler, only we'd call it 50 first dives.

[limeyx]

Why do ya think I keep wanting to return to Truk Lagoon???:lotsalove:

ha! But given my logic, you could just do all the dives at redondo beach and *think* you were in Truk (except you'd be freezing cold), then you'd save all that money :)

[Bismark]

But you might not remember being cold so were you really cold after all?