Not diving to greater than 30m/100ft unless with helium

[USdiver1]

We all know that too much of a good thing (O2 for example) is not a good thing. Likewise for Nitrogen. Not only do individuals have different degrees of susceptibility to nitrogen and oxygen toxicity but the same individual may have significant variations in susceptibility depending upon whether they are exerting themselves physically, are suffering from illness, stressors, etc. IMO any diver can choose to dive mixed gas to reduce their potential exposure to such a toxicity. It is not "weakness" it is "prudence", and should be seen as such.

Remember the Navy decompression tables were developed for men in their twenties, in excellent physical shape, and following the rules to a T. I know when I look in the mirror, I no longer see my twenty year old, great shape, self, and I would wager that the majority of you don't see that reflection either. We now use tables that are more prudent for our recreational diver selves. Is that a weakness?

 

[dumpsterDiver]

We all know that too much of a good thing (O2 for example) is not a good thing. Likewise for Nitrogen. Not only do individuals have different degrees of susceptibility to nitrogen and oxygen toxicity but the same individual may have significant variations in susceptibility depending upon whether they are exerting themselves physically, are suffering from illness, stressors, etc. IMO any diver can choose to dive mixed gas to reduce their potential exposure to such a toxicity. It is not "weakness" it is "prudence", and should be seen as such.

Remember the Navy decompression tables were developed for men in their twenties, in excellent physical shape, and following the rules to a T. I know when I look in the mirror, I no longer see my twenty year old, great shape, self, and I would wager that the majority of you don't see that reflection either. We now use tables that are more prudent for our recreational diver selves. Is that a weakness?

Well it sure as heck isn't " A STRENGTH" when you are old and fat and out of shape..

Only half kidding..

We all need to dive within our physical capabilities....

I love it when divers view having a low SAC as something to brag about. Is having a higher SAC a "weakness" or simply "prudence"?

 

[Akimbo]

… I have read that a small percentage of helium in a mix can make for safer diving (for recreational divers venturing between 100 fsw and 130 fsw)…

I’m not sure that the word “safer” is a good choice rather than the specific effect of potentially reducing Nitrogen Narcosis symptoms and gas density.

We all manage symptoms that diminish our peak performance. Many people feel comfortable driving a car after one small beer or with a head-cold, but we are not at peak performance. We are also compromised after getting some bad news, we have a mild headache, our cell phone rings, or we get a flat tire — but we manage. Look at moms with a carload of 6 year olds. That's management and probably more dangerous than a beer.

Managing mild symptoms caused by Nitrogen and/or Carbon Dioxide is a diving skill that is fundamentally no different than managing the distraction of a jelly fish sting. Divers need to learn to recognize and adapt to mild symptoms and distractions because you can’t always dive Trimix, have optimum lung ventilation, or avoid jelly fish.

… Question, would the NDL with such a trimix gas change the NDL from EANx 32 to make much of a difference (because of the helium)?...

It can, but not nearly as much as higher O2 in the mix. There are lots of decompression models but IMHO, not enough to get excited about in the 130' depth range.

 

[Dirty-Dog]

Remember the Navy decompression tables were developed for men in their twenties, in excellent physical shape, and following the rules to a T. I know when I look in the mirror, I no longer see my twenty year old, great shape, self, and I would wager that the majority of you don't see that reflection either. We now use tables that are more prudent for our recreational diver selves. Is that a weakness?

I see exactly the same 20 year old, great shape self.

Until I put on my bifocals...


Sent from an old fashioned 300 baud acoustic modem by whistling into the handset. Not TapaTalk. Really.

 

[JohnnyC]

I love it when divers view having a low SAC as something to brag about. Is having a higher SAC a "weakness" or simply "prudence"?

I like when people brag about having a low SAC rate and are constantly complaining of having a headache because they're retaining CO2.

"Oh, you have a low SAC rate? Cool story bro!"

 

[markmud]

(In part, editing performed by markm):

We all manage symptoms that diminish our peak performance.

Divers need to learn to recognize and adapt to mild symptoms and distractions because you can’t always dive Trimix, have optimum lung ventilation, or avoid jelly fish.

It can, but not nearly as much as higher O2 in the mix. There are lots of decompression models but IMHO, not enough to get excited about in the 130' depth range.

Thanks for your response Akimbo,

Your opinions from your quoted post have brought me full circle. I do manage the issues I confront while diving by using the available tools, training, and experience that I have gained to date. As you stated in general, and for me in particular, diving trimix is really not an option because it is not available to me where I like to dive. And I would get minimal advantage for the money spent.

markm

 

[Akimbo]

… I do manage the issues I confront while diving by using the available tools, training, and experience that I have gained to date…

I just realized that the most obvious and effective tool for managing Nitrogen Narcosis has barely been mentioned. Just go up. Symptoms are often reduced enough that a diver feels full relief after ascending 10-20'.

That’s one of the nice things about experimenting with Nitrogen Narcosis on wall and wreck dives. You can say “this is too deep for today” and still enjoy the dive. It’s not like we have something to be accomplished besides having fun. Don’t get caught up in the “grass is greener on the other side of the fence” syndrome. Besides, the other side of your depth fence usually proves to be grayer and more lifeless.

I also don’t want to completely diminish the value of Helium. Trimix for recreational divers (which includes most technical divers) is a tool and has its place, but it should be so you can cross your personal depth limit because there is something that you really want to see or experience. First you have to find those limits, slowly and carefully.

I believe that most people find that their depth limits are also very near their decompression and investment limits. A personal decompression limit is what you are willing to invest in hang-time versus bottom time plus the restrictions imposed on repetitive dives. Financial limits are considerable since crossing them will mean packing doubles and maybe slung bottles. It also means a lot of classes that are prerequisites to Trimix. Then there’s the cost of fills. Pretty soon you are also pushing very hard against the limits you impose on the time to a treatment chamber in case you get bent. There’s a lot more to the Trimix decision than just adding a little Helium to the mix.

 

[chrisch]

.....
I believe that most people find that their depth limits are also very near their decompression and investment limits. A personal decompression limit is what you are willing to invest in hang-time versus bottom time plus the restrictions imposed on repetitive dives. Financial limits are considerable since crossing them will mean packing doubles and maybe slung bottles. It also means a lot of classes that are prerequisites to Trimix. Then there’s the cost of fills. Pretty soon you are also pushing very hard against the limits you impose on the time to a treatment chamber in case you get bent. There’s a lot more to the Trimix decision than just adding a little Helium to the mix.

That's a really good point. The advantages of accelerating the deco with high O2 gas is a much better return on the training/cost for trimix (whether at 40m or 140m) and "technical" diving in general. Personally I like the option to add some He to the back gas from 35m onwards and to do that you need the training and knowledge to do so. That training and knowledge is also paid back many times over by knowing when you can leave out the He. I would encourage people to undertake the training even if they think they will not often get to dive trimix. A tool (in this case trimix) is only as useful as the operator's knowledge and skill permits. You then need to get the experience that enables good decision making. That sometimes means getting near the edge of what is comfortable. As you rightly say it is a more complex thing than just adding a little helium.

 

[Diver0001]

I'd like to hear people's thoughts on this but *not* tying back to TSandM as she was not unique in her approach of when to use helium.

DD's claim is that reluctance to dive to depths of greater than 30m/100ft without helium indicates unusually low tolerance for narcosis and therefore represents a weakness in a diver.

I'd like to know people's thoughts on the use of helium to mitigate the effects of narcosis and whether or not this is a "weakness" in a diver. I'd also like to know what alternative would be suggested.

I don't see it as a weakness. I see it as a "risk management" measure.

That said, I regularly (about once a week) dive to about 50m on air even though I'm trimix certified. For our weekly bimble the dive is deep but very straight forward and it's hard to justify paying >€100,- on gas for that. For other dives at this depth I would definitely use trimix. It depends a lot on what the objective and/or working phase of the dive looks like.

BTW, I'm not saying that anyone else should do what I do. I'm just coming clean.

R..

 

[Akimbo]

… BTW, I'm not saying that anyone else should do what I do. I'm just coming clean...

I’m not sure that is true, IF you include the “how you got there” part.

Without the benefit of personally knowing you or your diving history, your posts suggest that you are a prudent and experienced diver. 50M/164’ was the suggested recreational depth limit in Europe for a long time. Dropping to that depth when the ink is still wet on your OW cert is somewhere between ill-advised plain stupid. It is my impression that most people who progressively gain experience below 30M/100' will develop the skills to safely dive in that range.

But it isn’t just about managing Nitrogen Narcosis. Limitations imposed by gas management and decompression increase pretty rapidly past the 40M/130' mark — probably much faster than basic diver training of today can accommodate for most of the population.