Technical diving courses

[BigJetDriver]

AquaTec once bubbled...
first lets establish whats deep you stated [or someone did] that 100 feet is deep on air and that lower than that there should be helium in the mix.

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ADDED: Of course, we all realize, I believe, that we all did air to the recreational limit of 130 fsw for many, many years!

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If teaching was about the money I would be doing something that actually paid good money.

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ADDED: Too true! As we know, if you want to make a small fortune in the SCUBA business, start with a larger one!

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I do believe that when you are narced you are narced. I know a very active scuba instructor that gets narced at 80 feet; narced out of her gourd. Would you find it acceptable for her to dive up to 100 feet because it is considered NOT deep air? F**k no, she should dive to her comfort zone, where ever that is.

You would have us believe that she should be capable of diving to 100 feet because it is not deep, the same could be said for those who are not narced at 100 feet maybe they could dive a little bit deeper.

The subject of "Deep Air" is a contentious one. There are probably as many views on the subject as there are instructors. For myself, I am not a fan of "Deep Air", but then, from reading AquaTec's posts, he is not advocating its use to the exclusion of other "mixed" gases, which is quite a reasonable approach!

 

[cornfed]

AquaTec once bubbled...
I
I think 100 feet is not deep on air, if 100 feet is your depth. 130 is not deep but may be the limit for some, 150 is generaly the threshold for most divers, if that is your depth.
as for equivalent air depths i think 100 - 130 feet should be the standard, however with every standard there are exceptions.

Equivalent air depth or equivalent narcotic depth?

I was under the impression that the first lets you use your trusty old air tables and the other tells you how narced you are.

Cornfed

 

[gjmmotors]

the use of 28% to 21% (1.6ppo2) should be fine for that depth. However i was under the impression that tdi changed there depth restrictions this year, my adv nitrox class was a max of 130ffw.
The use of mix on relatively shallow dives (130fsw) would be a luxury that i cannot afford. about 60 of my dives this year have been to about 130 fsw, mix would add up if i wasnt mixing it myself.

-greg

 

[sheck33]

i think it is simple, deep air is something you get away with until the time you dont. I think a lot of divers are well aware of the potential problems diving deep air. If they still choose to do it that is their problem isnt it. I have done it and i am glad i got away with it, i do not dive deep on air anymore.
choices choices.......some choices are just better than others

 

[Braunbehrens]

AquaTec once bubbled...
I am happy to discuss deep air with you in a civil manner.

first lets establish whats deep you stated [or someone did] that 100 feet is deep on air and that lower than that there should be helium in the mix.

I think 100 feet is not deep on air, if 100 feet is your depth. 130 is not deep but may be the limit for some, 150 is generaly the threshold for most divers, if that is your depth.
as for equivalent air depths i think 100 - 130 feet should be the standard, however with every standard there are exceptions.

SNIP

I do believe that when you are narced you are narced, I know a very active scuba instructor that gets narced at 80 feet, narced out of her gord. would you find it acceptable for her to dive up to 100 feet because it is considered NOT deep air. f**k no, she should dive to her comfort zone, where ever that is.

you would have us believe that she should be capable of diving to 100 feet because it is not deep, the same could be said for those who are not narced at 100 feet maybe they could dive a little bit deeper.

AT, I am glad that you want to keep the discussion civil, after all we are only talking about diving. Maybe we can all learn something from this discussion.

You say that different people are narce'd at different depths. I am glad you brought this up, because I also know an instructor who gets narced very shallow. You are right, different people have different threasholds.

However, that is not where the story ends. The SAME person may be narced more or less on different days even though the depth is the same. What's worse, narcosis may manifest itself in different ways. Some days you may FEEL narced out of your gourd, as you say, on other days you may feel very comfortable and safe. BOTH are signs of narcosis.

My point is simply that narcosis is treacherous, and may not be obvious. 100 ft should be the maximum, IMO.

There is clear evidence that EVERYBODY is narced at 60 fsw.

I hope I was not rude in any way, I just wanted to mention these facts about narcosis. In light of them, I think any dive below 100 fsw is better done on trimix.

The problem with using nitrox, btw, is that oxygen narcosis is even harder to notice, and then there is the added problem of a high working PO2.

I am looking forward to your thoughts on this.

 

[AquaTec]

We are in agreement that everyone is narced, and every time you are narced the effects could be different, and at different depths. one time it may be pleasant and uphoric the next it may be panic.

it could happen at 60 feet or 200 feet on any given day.
this we are both in agreement with.

I will also agree that trimix is better than air on a dive where narcosis is a factor.

where we probably differ is where that depth is, and i may sound somewhat contradictory on this....for me the depth may be deeper than for others. I teach that deep air is anything deeper than 100 feet, and beyond 100 feet you will definetly feel the effects of narcosis.

i would not enforce the use of trimix at depth 100 and 200 feet i would insted explain the risks, the effects, and the conciquences of deep air diving. as i do believe that we are not all cut from the same cookie cutter, i believe that each diver makes their own decision on the type of dives they whish to do, the type of gear they wish to use, etc. i only educate them on the benifits of deficets of the different methods and ideas out there.

for me personally i will happily plan a dive on air and if i need to back off on the depth because the effects are different today than yesterday then i am happy to do that, my plan can change that way without regret or danger.

I also believe that there is a huge difference in people who dive a lot and have been diving for a while say 100 dives a year for many years, vs a person who has just recently strated diving and whants to start doing some deep diving right away because they just whent out and bought that new back plate and wings

 

[padiscubapro]

Braunbehrens once bubbled...


There is clear evidence that EVERYBODY is narced at 60 fsw.

.

All the studies I have seen reports of, say SOME (most do not to any real repeatable measurable degree) experience it that shallow, all the studies I have seeen show by 3.2 ATA of PN2 (100 fsw for an air dive) every individual shows measureable and fairly repeatable signs of narcosis.

ALso the problems with some studies doing the same skills the people tended to better over time.. Many people attribute this (incorrectly) to getting aclimated to the narcosis and learning to deal with it rather than the individual learning the skill to a point where its automatic..

Tasks requiring reasoning, generally no improvement was shown..

as a side note, To my knowledge there have been no studies I can verify that altering the PN2 by raising oxygen content had any effect on narcosis..

 

[MikeFerrara]

This is always a fun argument. As far as I know you're narced as soon as ambient presure increases. I wonder if we're narced at the surface. I've thought of having my son breath trimix while in school. LOL

The question is at what depth is it a problem? How much impairment can be tolerated? It seems to me you need to take the starting point into account. A simple well planned dive will require less thinking on your feet. A more skilled diver will be able to handle more problems automatically without the need for much thought. I've seen divers that I think had narcosis problems at 60 or 80 ft.

While I'm not in favor of deep diving on air, I don't see anything magical about 100 ft either.

All else being equal less N2 is better, but all is not equal.

I'm interested to see where these recreational trimix classes go. Around here you can't get trimix no matter how much money you have. If you can find some it'll cost you. In the 3 1/2 years I've had my shop I haven't sold a single tank of trimix except to some blending students who were mixing there own for their own trimix class.

Like it or not, diving below 100 ft without He isn't going away anytime soon.

 

[padiscubapro]

MikeFerrara once bubbled...
This is always a fun argument. As far as I know you're narced as soon as ambient presure increases. I wonder if we're narced at the surface. I've thought of having my son breath trimix while in school. LOL

The question is at what depth is it a problem? How much impairment can be tolerated? It seems to me you need to take the starting point into account. A simple well planned dive will require less thinking on your feet. A more skilled diver will be able to handle more problems automatically without the need for much thought. I've seen divers that I think had narcosis problems at 60 or 80 ft.

While I'm not in favor of deep diving on air, I don't see anything magical about 100 ft either.

All else being equal less N2 is better, but all is not equal.

I'm interested to see where these recreational trimix classes go. Around here you can't get trimix no matter how much money you have. If you can find some it'll cost you. In the 3 1/2 years I've had my shop I haven't sold a single tank of trimix except to some blending students who were mixing there own for their own trimix class.

Like it or not, diving below 100 ft without He isn't going away anytime soon.

Mike,
I wasn't implying 100fsw was a magical number just by this point it can be consistently measured in all individuals.. The level of narcosis will differ but it is detectable.. I don't believe an END of 130/40m is a problem either, I think its a reasonable limit for most people and dives.


Personally, while I'm at home and on my CCR all dives I do have He in it.. I bank 21/40 (I hate that nomenclature!) and my RB uses such little gas there is no reason not to use it.., even doing 60m/200 fsw dives I use under 4 cuft (probably closer to half of that on most dives) of diluent gas per dive.

When I travel thats another story..

I don't mind doing non He dives to 50m(and when necessary and conditions and support are available I will push it deeper), but I definately prefer the He in the mix..

 

[Doppler]

It will be interesting to see what changes to this new ethic may be made as the cost of helium rises over time. For many years, my gas supplier was charging about $68 Canadian for a 8.5 cubic meter cylinder of He. The basic market rules of supply and demand have begun to put upwards pressure on that price. Not sure what shops are charging for "recreational mix fills" but it's going to be interesting to see what changes are made to "dive goals" as the price of a fill to dive to, say 115 fsw, climbs up to the cost of the charter to get there.

Anyone here ski? Do you tackle black diamonds with or without a helmet... do you wear a helmet on a blue or a green on your favorite hill?

Can't think of it in any other terms... except I see a lot of people who should be diving the "bunny hill" trying to dive the "couloirs"