Deep Air Diving - thoughts

[grazie42]

Most agencies recommend maximum end between 100-130ft and except for differing views between divers as to the narcotic effects of O2 arguing about it seems a bit silly?

For what it´s worth I was taught to use PO2 of 1,2 on my recent RB-course and many RB-divers stay at 1 on longer dives...I wouldn´t want to do that on OC though...

 

[rjack321]

Others may read this differently, but that sounds preachy as hell to me. I have no idea if you are GUE or not, but your arguments sound like they are straight out of the textbook, and your tone is exactly the same as other preachy GUE divers - rjack, "SparticleBrane", John B, RTodd etc etc.

I'm not sure where you read preaching? But telling someone what I do, does not make a judgment about what they choose to do.

Bismark has been holding down the fort here with good arguments for comparatively shallow recreational depth range ENDs on deeper dives, so I haven't felt the need to chime in much. I find it particularly interesting that despite that lack of participation I am viewed as a "religious" fanatic.

 

[rjack321]

45% helium is too high for me, I prefer 18/30. 30% helium is sufficient for 200 feet.

"Too high" - what is the basis of this conclusion? Cost? Value? Deco plan changes? Something else?

I know English is not your 1st language and I just want to be clear on why 30% is acceptable and 45% is not.

(Personally I don't think a 130ft/40m END is rediculous, higher than I'd prefer, but not laughable)

 

[Tomeck]

"Too high" - what is the basis of this conclusion? Cost? Value? Deco plan changes? Something else?

I know English is not your 1st language and I just want to be clear on why 30% is acceptable and 45% is not.

(Personally I don't think a 130ft/40m END is rediculous, higher than I'd prefer, but not laughable)

Becaause helium is very expensive and it is not very useful, because END is 130ft/40m, it is reasonable like recreational diving.

 

[Bismark]

Actually I'm not and my balls are not made of steel. I'm an average guy, perhaps with a little more tolerance and acceptance of danger than the next guy, but I do feel that some people are wrapping themselves in cotton wool and the whole planet seems to be getting more and more...I cant even find the word for it.

Not all of us have access to reasonably priced helium and either we don't do the dive or we dive deepish on air. At the end of the day we want to explore and therefore we choose to do it.

Many people have died discovering the delights of our world in all aspects of exploration, land, sea and air and more will probably continue to do so. If these people hadn't done it we would probably still be living in caves. It just seems to me that there is a lack of the "explorer gene" these days and it's becoming more predominant that people actually want to discourage "adventure". Its quite sad really.

But hey if you ain't comfortable doing a 50 metre air dive then by all means don't do it but to rag on others and call them idiots for doing so...?

So you flew fast jets...very cool but very dangerous. I'm sure some people would call you an idiot for sitting on top of friggen great jet engines, fuel and weapons...not me....I think you are marvelous (I really do - I love planes and weapons).
Just curious as to why you think flying a fast jet is "safe" but diving past 30 metres on air is stupid?

You might be surprised as to the personality types you will find flying military jets. We are a long way from "kick the tires and light the fires" and while there is definitely an element of risk and danger, the amount of planning that goes in to the simplest of flights makes a 250' trimix dive look like a walk in the park.

The entire idea is identify the elements of risk and try to reduce them as much as you can through planning and forethought. There are enough things to go wrong that can bite you in the ass in both flying and diving that I think it is a hell of a good idea to elminate the "easy" things. I can and do remove as much of the risk of narcosis as I can by keeping my END low. I can and do remove as much of the risk of C02 build up low by keeping my work of breathing down (IE- scooter if possible- high HE mix's regardless) and I keep my P02 low on the working portion of the dive and adopt a conservative approach to my deco P02. I consistently practice standard emergency responses and make troubleshooting valve failures a regular part of my actual diving and home study. I continue to read and study the latest research and literature and continue training with the best people I can find. Someone always has something new to offer.

Long story short, you would find the modern military pilot would approach his training the same way as I approach my technical diving. This is not supposed to be an adrenaline sport. As far as the lack of the "explorer gene" I think what you are really missing is the "indiana Jones" style of exploration. Those were the "kick the tires and light the fires" group who were often marking uncharted territory and the majority of them paid the price for their approach. Absolutely they paved the way for others, however the modern explorer has to begin where they left off and they "left off" where they did because a "hail mary" and "damn the torpedos" approach only goes so far. Now we are having to move past their benchmarks but it requires a hell of a lot more planning. Diving to 200' was pretty amazing when they first did it, but the next 400' or 600' are a whole different ball of wax.

To paraphrase Isaac Newton, we are seeing further because we are standing on the shoulders of giants. I think if you were to give a lot of these early pioneers of both flight and diving the technology and knowledge we have today, you would find them grab it with both hands and use it to see further.

 

[Bismark]

Becaause helium is very expensive and it is not very useful, because END is 130ft/40m, it is reasonable like recreational diving.

Not sure if this is a language thing again. What do you mean when you say helium is "not very useful"? Do you mean the extra 15% in this case?

One thing JHoey hinted at in his post but didn't get into very much is the utility and convenience of the GUE standard gases. If we can agree that nitrox is a better breathing gas for diving than is air and that 32% with a reasonable P02 (couple of assumptions here that some may challenge but stay with me here...) presents an MOD of around 100', then....

If you bank 32% in your banks for most of your regular dives.......

Then you take your empty trimix dive cylinders and fill them with 35% Helium, or 45% helium...etc.

Now top those cylinders up to operating pressure with your banked 32%. What do you suppose the finished mixes are? How about 21/35, 18/45, etc...... Pretty nifty right? And then you maintain that 100' END and this gives you your operating range and max depth of the gas.....all the while maintaining a working P02 of 1.4 max. Contrast this with the "best mix" approach where you pretty much have to reinvent the wheel for each different gas mix. Not saying the math is tremendously hard, but why go to all the work all the time?

Moreover, by adopting standardized gases, as Jeremy mentioned, dive planning becomes a snap. How deep is our wreck? Between 140' and 190'...."perfect, then we use 18/45". We want to dive a wall in the 110' to 140' range? No brainer.....21/35. And we were able to mix it without a lot of drama, just by adding banked 32% to our 35% and 45% helium. No high pressure 02 involved.

For the vast majority of technical diving, a few standardized gases cover the whole range. From here you have someplace which gives you a consistent base to start with recognizing how your own body reacts to deco. You have a solid baseline from where to start "massaging" your own deco profile. I am in my early 40's and have found that 4 solid trimix dives in a weekend tire me out a lot, and I prefer to stretch out the shallow portions of my deco. Just what works for me.

The rocket science math whiz type here will note that 30/30 does not fit this same formula. That is a different thread altogether and maybe Rjack will chime in here

 

[Tomeck]

Not sure if this is a language thing again. What do you mean when you say helium is "not very useful"? Do you mean the extra 15% in this case?

One thing JHoey hinted at in his post but didn't get into very much is the utility and convenience of the GUE standard gases. If we can agree that nitrox is a better breathing gas for diving than is air and that 32% with a reasonable P02 (couple of assumptions here that some may challenge but stay with me here...) presents an MOD of around 100', then....

If you bank 32% in your banks for most of your regular dives.......

Then you take your empty trimix dive cylinders and fill them with 35% Helium, or 45% helium...etc.

Now top those cylinders up to operating pressure with your banked 32%. What do you suppose the finished mixes are? How about 21/35, 18/45, etc...... Pretty nifty right? And then you maintain that 100' END and this gives you your operating range and max depth of the gas.....all the while maintaining a working P02 of 1.4 max. Contrast this with the "best mix" approach where you pretty much have to reinvent the wheel for each different gas mix. Not saying the math is tremendously hard, but why go to all the work all the time?

Moreover, by adopting standardized gases, as Jeremy mentioned, dive planning becomes a snap. How deep is our wreck? Between 140' and 190'...."perfect, then we use 18/45". We want to dive a wall in the 110' to 140' range? No brainer.....21/35. And we were able to mix it without a lot of drama, just by adding banked 32% to our 35% and 45% helium. No high pressure 02 involved.

For the vast majority of technical diving, a few standardized gases cover the whole range. From here you have someplace which gives you a consistent base to start with recognizing how your own body reacts to deco. You have a solid baseline from where to start "massaging" your own deco profile. I am in my early 40's and have found that 4 solid trimix dives in a weekend tire me out a lot, and I prefer to stretch out the shallow portions of my deco. Just what works for me.

The rocket science math whiz type here will note that 30/30 does not fit this same formula. That is a different thread altogether and maybe Rjack will chime in here

Before my trimix certification, I often dived more than 130 feet with air and my deepest dive with air is 233 feet. I learned much how to manage with narcosis. I think it is not a good idea to get a trimix certification without experience with narcosis at more than 200 feet, because one feels dependent with helium for deep diving.

 

[peterbj7]

Bismark - most of what you are saying, though plausible at a level, assumes unlimited funds and total availability. There are many parts of the world, and I live in one of them, where helium is rarely available and horrendously expensive when it is.

I'm a bit confused about your recommendations on dive planning. Are you saying that being able to have a handy look-up table (because you've artificially restricted your choices) makes planning easier? That's not a message I like to get over to my students, to go for the approach that gives the easiest calculations or none at all. I have absolutely no difficulty with dive planning regardless of the gases available to me, and having recognised what my preferred max pN2 normally is I can easily calculate whether the gas available to me will enable me to perform a particular dive.

I'm not surprised that four "solid trimix dives" in a weekend are tiring. In Britain we usually restrict ourselves to one per day.

 

[Bismark]

As to dive planning, I am saying that the convenience of having standardized gas mixes that can be blended as easily as I mentioned provides several advantages. First, ask your self how many times you have shown up on a technical boat and found as many different gas mixes as there were people. I am sure you know the implications of this from a safety point of view. I like knowing that when I dive everyone else is breathing the same gas (bottom mix and deco gas) and that if **** hits the fan, I don't have to worry if I have to do some drastic deco calculations based on different bottom mixes and deco gases. This is not something I would want to worry about in a emergency. For those of us who dive with standard gases, we don't need a handy look up table as there aren't really that many choices. Again as I mentioned, I spend more time becoming familiar with the way my body reacts to a particular dive profile and then massage the deco when necessary. If I was to use a "best mix" for every dive, I would have no bench mark and I would introduce a high level of "variableness" into understanding how my body would react to a specific dive. Of course, over time you could do the same thing for just about an unlimited number of gas and depth combinations, but that would be a hell of a lot of trimix dives and I don't know how practical that would be. I prefer to eliminate the variables I can control and establish some kind of baseline which I can then use to move forward and look at the variables I have less control over such as currrent, etc.

I am not in anyway telling anyone they just need to memorize some tables and then forget everything else. Those calculations provide the base for understanding mixed gas diving and are absolutely essential to anyone who wishes to dive trimix. However, once I learned my single digit multiplication tables, I don't use a calculator for the more simple multiplication I use in everyday life. I still pull out the calculator for more difficult math but "re-inventing the wheel" each time I need to do some simple math is not something I want to waste my time doing.

As far as artificially restricting my choices, I think you may have misunderstood me. My standard gases cover the complete range of my trimix diving and provide me with what are essentially 50' windows before I need to change gases. This "window" is very useful for the exploratory trimix diver. For example, two weeks ago we were diving in the Red Sea and diving on a wreck that sits on the sand at 270'. There were 9 trimix divers and 6 of them were diving the wreck in the 240' range. I was tired from the previous two weeks and felt I was a bit dehydrated so I elected to dive in the 170' range so that we would get more of a birds eye view of the wreck which lays on its side. Our team of three were diving 18/45. We descended and found that 170' was not deep enough to truly get a good view of the wreck. We descended for a few minutes into the 190' range and had a great tour of the wreck. We recalculated our deco and surfaced with some great memories. Because our gas had a useful range that kept our p02 and END within the limits I feel comfortable with, adjusting our dive in mid stride was a non event. I understand your view that using standardized gases appears to be a "short cut" to understanding and doing the calculations and this is a commonly held view. However, once you do know the math and the formulas and the calculations, why go through them every dive if you don't have too?

Now on to the first point of your post, regarding the cost and availability of trimix. That one I don't have an easy answer for. (really, really wish I did) I have paid as much as $4.50 a cubic ft for He in some remote locations and this puts a serious crimp on anyone's mixed gas diving unless you are very rich. I am not. Availability is always a function of $$ and sometimes those $$ are just stupid expensive. I couldn't even guess what it would cost to bring HE to your location but it sounds like it would be prohibitively expensive. So what do you do? Sorry I don't have the answer here for that. My personal preference would be not to do the dives as I would not be comfortable with the degree of risk. Clearly, this is a personal preference and one to which you and others have chosen differently. Fine, for you and me we have made these decisions from a position of being informed of all the sides of the argument. My concern, which I have stated many times previous is that new divers are not being presented with all the information and quite possibly accepting a higher level of risk then they would be comfortable with had they known all side of the argument. In a nutshell, my major point of concern is with those who present deep air diving from a "I do it and haven't died and therefore it must be perfectly safe" are not providing their students with the full picture and allowing them to make informed choices about setting their own personal level of risk. Posts from those who provide a supply of anecdotal evidence about their personal diving are akin to you and me sitting around in a bar and telling each other about all the times we drove home drunk from the pub without incident. For someone who had no other source of knowledge about this, he or she would probably decide that it was a non-risky endeavor.

I don't have any personal stake in this whole thing: I don't own a HE generation plant or sell mixed gas. I am only concerned from the point of view of an educator that we present all sides of the argument to someone who is unaware so they are able to make informed decisions regarding their own level of risk.

BTW, out of curiousity, based on your experience and considering where you are diving, etc., what is your personal END choice? You mentioned you had a Pn2 comfort zone. Also, since you don't have mix available to you where you are, what are your thoughts about deco'ing out on air from bigger dives?

 

[peterbj7]

To answer your last question first, I normally reckon narcosis starts at around a pN2 of about 3, which equates to an END of maybe 28 metres in salt water. Any point from then on I prefer mix if available, though as I said that often isn't the case. I'm a lot more prepared to use helium if I'm diving closed, because I use very little of it. The helium cost alone of a twinset used to dive OC to maybe 75 metres here exceeds $300.

Interestingly, you and GUE refer the effects of nitrogen by the END even though you never dive air, whereas I do dive air most of the time yet don't use END but prefer to think of pN2. Rather perverse!

Taking your example of a 170' dive that became 190', it's fortunate that your depth flexibility extended deeper rather than shallower. That's something I would have specifically borne in mind when choosing the mix for that dive. The end result would be pretty similar to what you did, just the logical process of getting there would have been slightly different. Though my biggest concern with changing the dive would have been available gas rather than degrees of narcosis. That and keeping oxygen within safe limits, a trivial but important consideration when going deeper than planned.

I take your point about standardising gases when diving as a team, and I do the same. I just don't necessarily use the same mix between different dives. Other aspects of GUE/DIR also kick in there, as standard gear configuration within a team engaged on a significant tech dive is also valuable.

I think at the end of the day our diving philosophy and practices probably don't differ much. It's coincidental (because I did courses with him) that I share Tom Mount's philosophy on dive planning, which is that there is rarely just one "right" way of doing anything, and you should experiment when circumstances permit as you might find a way that's better than what you did before. Before I even met him that was how I thought, and still do.

Incidentally, you think $4:50/cu.ft. is expensive for helium. Here it costs almost $13 per cubic foot.