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

[tomfcrist]

ART is Advanced Recreational Trimix. With IANTD a diver can choose: Adv. nitrox or adv. recreational trimix course. The art course goes to 48m max with END of 24m max and at least 21% oxygen in the mix (24% in course).

OK, so trimix/helitrox....I get it.

 

[kensuf]

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.

OK, I'll play. My thoughts..

Saying there's a "weakness" in a diver that chooses to use helium is stupid -- it leads to a herd mentality that can be dangerous -- "What, are you a chicken?" You should never call someone weak for wanting to mitigate risks.

As for my thoughts on using helium to minimize the effects of narcosis, and my personal decisions, I will say "it depends on the dive plan, my dive team, the site conditions, and the risk I'm willing to take." I need to also add that I have a fair bit of deep air diving background, to depths shallower than "completely stupid" but definitely deeper than "he's a moron."

Back in the stone ages, we used to switch to air at 190' when coming up from deeper trimix dives. For many reasons, I wouldn't even begin to consider coming off a helium mix to air at 190' now, and would stay on trimix to around 90'. So for deeper trimix dives, I'm using helium deeper than 90'.

Warm clear Caribbean diving where I'm just screwing around and all I have to do is go up in the event of an emergency, I probably wouldn't blink at a dive plan sans helium to a depth of 170-180'. I might have even done a dive or two in that range on air this past summer in Belize.

Cold, dark, site? I'm probably using helium below 100', and definitely below 120'.

Cave? Probably using helium below 120'. Definitely using it below 140'.

So.. It depends.

 

[PfcAJ]

I believe in the benefits of helium enough that I routinely use 15/55 on 100' dives and shallower without a second thought.

10/85 at 10ft or youre a sissy.

 

[jadairiii]

Since this is a vintage 90's discussion, here is some 90's music to enjoy while reading people claim they are good on air

https://www.youtube.com/watch?v=YyDqoLimejg
[video=youtube;YyDqoLimejg]https://www.youtube.com/watch?v=YyDqoLimejg[/video]

 

[wedivebc]

Unfortunately, too few divers allow themselves the time to learn the difference between elevated CO2 and the onset symptoms of narcosis. Elevated CO2 is especially a problem among those that obsess over their RMV instead of adequate lung ventilation. The symptoms are often indistinguishable, until you overtly modify your breathing to reduce CO2.

CO2 symptoms can go away with proper breathing and can occur on Trimix or HeO2. IGN (Inert Gas Narcosis) does not, though the intensity often reduces. There’s a lot more to narcosis management than just switching mixes. It is also about learning to manage yourself under stress.

IGN is not a weakness or a strength, only a human characteristic that must be managed.

Wow, you have just caused me to have an eureka moment!
I have always wondered why I felt less narced when diving rebreather than when diving OC and it never occured to me that I breath differnetly on CCR than on OC and therefore more likely yo retain CO2. Thanks.

 

[MXGratefulDiver]

I do not have any deep dive experience with Lynne--the deepest we ever did together was about 100 feet. I do know the things she said in support of the GUE limit of 100 feet END. For part of our time as friends I was also associated with UTD and had a similar limit. In all my UTD dives, I was not allowed to go below 100 feet without helium in the mix. She and I talked about it. My impression is that she was not any more affected by narcosis at those 100-130 foot depth than the average diver. My understanding instead is that she ascribed thoroughly to her GUE teaching and thought the degree to which the average diver was incapacitated by narcosis at those depths was too much. Thus, the degree to which she was incapacitated had to be too much, even though it was no more than what most other divers experience. I don't feel comfortable putting those words in her mouth, though, and devoutly wish it were not necessary. I don't see any reason to speculate on some sort of narcotic episode--it is unfounded and uncalled for.

Nailed it ... there was no "weakness", nor increased susceptibility involved. Nor was her position due entirely to the teachings of her preferred agency. It boiled down to what she considered an honest risk assessment ... what she considered acceptable risk, and how to manage it.

... Bob (Grateful Diver)

---------- Post added October 7th, 2015 at 12:40 PM ----------

10/85 at 10ft or youre a sissy.

... you might pass out ...

... Bob (Grateful Diver)

 

[oldschoolto]

I never understand the problem of pointing out the difference in people... We are not all the same... Some people are better suited to deal with deep air diving than others... John Chatterton talks about diving the Doria on air and (210 feet) needing to recall deck plans and pathways out... And he has maybe 100 dives on her... ALL ON AIR... I've got a pile of salvage wreck dives at 160- 180 feet in the northeast... Diving navy tables on air... To say it should not or can't be done is trying to rewrite history...

Jim...

 

[RJP]

I believe in the benefits of helium enough that I routinely use 15/55 on 100' dives and shallower without a second thought.

What's a 15/55 fill cost?

 

[rx7diver]

What's a 15/55 fill cost?

The cheap approach:

1. Start with "empty" cylinders.
2. Add He until 55% full.
3. Top up with EAN36.
4. Analyze. Your mix will be ~Trimix 16/55.

So, cost depends on no. cu ft He, no. cu ft EAN36, and labor.

EDIT: Oh, and don't forget the cost for deco/washout gases. Multiple deco/washout gases is probably best, since you really don't want to go from FHe = 0.55 *directly* to a deco/washout gas having FHe = 0, I understand.

Safe Diving,

rx7diver

 

[dumpsterDiver]

Nailed it ... there was no "weakness", nor increased susceptibility involved. Nor was her position due entirely to the teachings of her preferred agency. It boiled down to what she considered an honest risk assessment ... what she considered acceptable risk, and how to manage it.

... Bob (Grateful Diver)

Bob (Grateful Diver)

So she believed that 100 ft was too deep for her based on her personal experience and determined that air below 100 was not worth the risk __regardless of what some Agency said about it. As we see in this thread some people go through the same Analysis and draw a different conclusion,

The reason I raised the issue is that someone who gets drug down 30-ft deeper than they feel is safe or responsible ..will probably be psychologically stressed by the event. Similarly, with exceedance of the MOD of the mix.,.could be expected to represent an additional mental stress factor.

So the psychological aspects of these divergences from plan might have been more significant than any physiological impacts, for hér ?? maybe???