shugar
Contributor
bad air here is a shop-closer... word travels too fast in the dive community about an op pumping bad air and you can expect that in 2 weeks they're outa businessae3753:
Jag
PS
good thing your bud was on better air
What is the PADI "deep" specialty?
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Jag
PS
good thing your bud was on better air
shugar
Contributor
hey, that sounds interesting... how'd you do that?dsaxe01:
Jag
Since I do not know you, I used in the example the average value of 20 liters/min.
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miketsp:
OK ... I can buy that.
What I was responding to was your previous statement ...
I'm not necessarily against people going deep on air ... but I don't recommend it on a single AL80. First, because it probably won't be adequate gas to get you out of a jam at depth (especially in an air share situation), and second because if for some reason you lose your gas supply you have no redundancy.
I'd be willing to bet that folks don't routinely dive to the V17 Corvette on single AL80's. More likely they're using doubles, or a larger single cylinder with a backup bottle.
I'm not of the camp that believes deeper dives require a specialty gas ... sure, it's better but as you say in some parts of the world it's unavailable. As long as you're trained to handle deco, properly equipped, and properly prepared, then it's a personal decision.
On the other hand, doing a dive that deep on a single AL80 would suggest to me that the diver is not properly prepared or properly equipped. Chances are they're also not properly trained ... or they'd know better than try something like that.
... Bob (Grateful Diver)
Gee, what have I started 
Yes, I realize (as I stated) that this instructor didn't act prudent -- and as an instructor, I'll not do with my students as he did with me. As a diver, I'm also more responsible. What I did point out was just the mere fact, that it had been done (!). It's by far going beyond what was reasonable: a "trust-me" dive as my first OW dive -- in conditions where today, I'd not even go. (Btw., the dive was briefed as "follow me, and signal when you've got X bar left")
I do deep air (60m -- that's roughly 190 ft, I am told) if no other gasses are available. However in doing so, it's with a strict plan, strict equipment, ample redundancy and large reserves. And, it's with a deep (no pun intended) knowledge of how I act when subject to narcosis -- based on experience. Part of that is also knowing when to call a dive. My rule-of-thumb is, that if I hear that little voice asking "I wonder if it's time to call the dive or not", then it's called.
There's nothing wrong with doing deep-air. However "deep" depends on training, on experience, on how one deals with narcosis (we're all affected, but some can "work through it" differently than others), on ones buddy etc.
Just as an example: 60m on air to me equals 2x18l, at least 2 of everything (bouyancy devices, 1. stages. 2. stages, spg's, dive-plans/wetnotes etc), a buddy I know on the same depths from previous dives with similar config and at least the same training, a plan calling for egress of both divers with 1/3 still to spare (!) -- and so on. You get the picture.
Trust-me dives are bad. Imprudent gas-mgmt is bad. Irresponsible instructors are bad. And irresponsible students are bad too: I was at fault for not questioning the plan and calling the dive then.
(But make no mistake about it: 60m on air is much less enjoyable than 60m on He. One spends amazingly many brain-waves working through the narcosis on air, which could/should be spent on enjoying the scenery...)
Yes, I realize (as I stated) that this instructor didn't act prudent -- and as an instructor, I'll not do with my students as he did with me. As a diver, I'm also more responsible. What I did point out was just the mere fact, that it had been done (!). It's by far going beyond what was reasonable: a "trust-me" dive as my first OW dive -- in conditions where today, I'd not even go. (Btw., the dive was briefed as "follow me, and signal when you've got X bar left")
I do deep air (60m -- that's roughly 190 ft, I am told) if no other gasses are available. However in doing so, it's with a strict plan, strict equipment, ample redundancy and large reserves. And, it's with a deep (no pun intended) knowledge of how I act when subject to narcosis -- based on experience. Part of that is also knowing when to call a dive. My rule-of-thumb is, that if I hear that little voice asking "I wonder if it's time to call the dive or not", then it's called.
There's nothing wrong with doing deep-air. However "deep" depends on training, on experience, on how one deals with narcosis (we're all affected, but some can "work through it" differently than others), on ones buddy etc.
Just as an example: 60m on air to me equals 2x18l, at least 2 of everything (bouyancy devices, 1. stages. 2. stages, spg's, dive-plans/wetnotes etc), a buddy I know on the same depths from previous dives with similar config and at least the same training, a plan calling for egress of both divers with 1/3 still to spare (!) -- and so on. You get the picture.
Trust-me dives are bad. Imprudent gas-mgmt is bad. Irresponsible instructors are bad. And irresponsible students are bad too: I was at fault for not questioning the plan and calling the dive then.
(But make no mistake about it: 60m on air is much less enjoyable than 60m on He. One spends amazingly many brain-waves working through the narcosis on air, which could/should be spent on enjoying the scenery...)
voop:Gee, what have I started
There's nothing wrong with doing deep-air. However "deep" depends on training, on experience, on how one deals with narcosis (we're all affected, but some can "work through it" differently than others), on ones buddy etc.
Studies show (I've listed some of them in the past) that we can learn to compensate for narcosis when performing certain types of task essentially by sacrificing speed for accuracy or the other way around. It's like learning to let yourself in the front door, in the dark, while drunk. With practice it can be done. It's a rote task and after a while doesn't require any thought at all.
However, studies also show that the one thing we can't learn to do effectively while narced is improve our ability to think and solve new problems. Reasoning and awareness suffer and I haven't ever seen any evidence that there is any amount of training or experience that can help.
Now it could be that you could spend your whole diving career swiming in circles blitzed out of your mind without ever having a problem that requires any reasoning but if you do you will be at a real and measurable disadvantage.
miketsp
Contributor
NWGratefulDiver:
You do in fact see a lot of AL80s but normally at least one diver in the group will have doubles, manifolded or independent, and somebody carries an O2 or Nitrox cylinder for the final deco stops. Plus they normally hang extras at one of the intermediate deco stops.
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