Reaching Greater Depths

[stuartv]

Are the tools you are talking about Tech training and diving with Trimix? Or CCR? Or something else?

Also, are you saying that anyone would be impaired at 100 feet to the same degree as you are? Or might some people be equally impaired at only 80 feet? And others able to go to 130 and still be less impaired than you are at 100? Should I feel like I have an unsafe instructor if he wants to take me to 130 at the end of a Deep Diving full certification course (when I am eventually ready and able to take it)?

 

[boulderjohn]

Are the tools you are talking about Tech training and diving with Trimix? Or CCR? Or something else?

Also, are you saying that anyone would be impaired at 100 feet to the same degree as you are? Or might some people be equally impaired at only 80 feet? And others able to go to 130 and still be less impaired than you are at 100? Should I feel like I have an unsafe instructor if he wants to take me to 130 at the end of a Deep Diving full certification course (when I am eventually ready and able to take it)?

This is a question of great and highly contentious debate. Some people and agencies are very, very strict about a 100 foot limit without the benefit of helium. Others believe that is being overly cautious. I would hope that before your instructor takes you to 130 feet, the two of you will have a good conversation about the pros and cons of such a dive, and you will not do the dive unless you are completely comfortable with it. Your instructor should not force you to that depth unless you are OK with it.

 

[TSandM]

Narcosis is individual AND variable -- some people are more susceptible, and people vary in their response on different days and under different conditions. I believe, and the agency with which I did most of my training also teaches, that most people are sufficiently impaired below 100 feet that diving there should be avoided as a general principle. Helium is available and definitely reduces narcosis. On the other hand, it is very expensive, and requires excellent buoyancy control to use it safely.

I would not go so far as to accuse your instructor of doing something absolutely unsafe. But I would perhaps consider what he would do unwise and unnecessary. In my agency, you would not do a 130 foot dive until you were competent to dive helium, which involves good buoyancy, tolerance of task-loading, and good situational awareness. Don't those sound like things you would want for doing very deep dives?

 

[Kevrumbo]

The deeper you go on Air Bottom Mix, the less physical activity and cognitive task loading you should electively be doing. If you're going to do something complex like an initial first time overhead penetration with decompression afterwards for example --you should be using Trimix.

 

[Dr. Lecter]

Narcosis is individual AND variable -- some people are more susceptible, and people vary in their response on different days and under different conditions. I believe, and the agency with which I did most of my training also teaches, that most people are sufficiently impaired below 100 feet that diving there should be avoided as a general principle. Helium is available and definitely reduces narcosis. On the other hand, it is very expensive, and requires excellent buoyancy control to use it safely.

I would not go so far as to accuse your instructor of doing something absolutely unsafe. But I would perhaps consider what he would do unwise and unnecessary. In my agency, you would not do a 130 foot dive until you were competent to dive helium, which involves good buoyancy, tolerance of task-loading, and good situational awareness. Don't those sound like things you would want for doing very deep dives?

Except that GUE is in a distinct and--aside from its members anecdotes about their levels of impairment--factually unsupported minority as to considering 100-130' dives on non-helium gasses "very deep" and unsafe. On the other side of the coin are the vast majority of divers trained by agencies like IANTD, TDI, PSAI, PADI, NAUI, etc ad nauseam, none of which are taught that particular bit of DIR dogma. Hell, last I checked PSAI is still teaching all levels of Narcosis Management

There is nothing wrong with adopting the GUE dogma on this point, but implying that there's any rational basis for not doing so being unsafe seems like passive-aggressive trolling for GUE.

 

[tomfcrist]

Dr lecter,

On the recreational side you are correct, however NAUI is very clear on their opinion of narcosis as it applies to tech dives...past 130=add helium. NAUI is very DIR on the tech side of the house. Not as strict as GUEs 100' stance, but every agency varies as we all know.

 

[Dr. Lecter]

Dr lecter,

On the recreational side you are correct, however NAUI is very clear on their opinion of narcosis as it applies to tech dives...past 130=add helium. NAUI is very DIR on the tech side of the house. Not as strict as GUEs 100' stance, but every agency varies as we all know.

Like I said, 100' is a relatively lonely cut-off.

I've always suspected the optics of being able to sniff words to the effect of 'We don't dive air...above one shallow limit, we the Enlightened use NITROX; and anywhere below it we dive HELIUM!' were behind this bizarre affectation amongst the DIR-minded. But if someone has convinced themselves they're truly "farm animal stupid" without helium past 90', that's their business and I leave them to enjoy diving as they see fit. When they start calling things other than what they do somehow more unsafe than getting in the water to begin with...I get more vocal.

 

[TSandM]

I have made several errors that could have been lethal, while cave diving on Nitrox in the 90 to 100 foot range. I do not make those errors when diving shallower. Therefore, I have concluded that I, personally, am an unsafe diver for any kind of challenging dive at 100 feet on Nitrox. I am always unaware of my level of impairment; I am simply horrified by what I have done when I return to depths where I can think. I may very well be unusually susceptible to narcosis -- my husband functions far better than I do at those depths. My opinion is based on my own experience, and the discomfort I have with the fact that I don't feel any different when I'm stupid.

The agency I dive with agrees with me. It is definitely a minority position, and I did not say it was anything else. But there are a lot of GUE instructors and GUE divers who conduct their diving according to that principle. I am not alone.

 

[Rhone Man]

Well, I think if there is one thing that everyone can agree on, it is that we will never get everyone to agree upon what depth (in absolute terms) divers should be breathing helium mixtures.

But it may be worth rehashing all the old arguments for the benefit of the OP, who may not have heard them before.

 

[Storker]

I don't feel any different when I'm stupid.

Do you think you're the only one?

Don't bother to answer that, it was a rhetorical question. I'm rather convinced that quite a few of the "I don't get narked" people are narked, but aren't aware of it. Since my job sometimes requires rather intense mental efforts, I'm rather aware of whether or not my mind is working at full speed, and I'm often able to notice mental impairment before it's really debilitating. And I'm not saying that I'll be able to do that every time; I'm quite certain I've been somewhat narked at 30m without really noticing it.

---------- Post added November 14th, 2014 at 08:59 AM ----------

he would take me down to 130 and have me stay down right up to the NDL.

On an Al80? What would be your minimum tank pressure at that depth? You should have sufficient gas to handle a situation involving stress, elevated gas consumption and donating gas while doing a controlled ascent, preferably with a safety stop before surfacing.

For me (I have an RMV of 14-17 SLM; 0.5-0.6 cuf/min), that would be between 1750 and 2000 psi.