200' on air for 5 min bottom time?
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Dsix36
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In this new and modern age of voodoo gasses, there is absolutely no viable reason to use air at a depth of 200'. Nitrox is better and trimix is what you really need.
I refuse to give an answer that might give you stupid ideas about actually making that dive.
I refuse to give an answer that might give you stupid ideas about actually making that dive.
chrpai
Contributor
Bob DBF
Contributor
I'd be more worried about having it together enough to remember to stay 5min and start back up. I was doing some 150' dives on air last fall and it took a lot of work up dives to function at that depth, and I wasn't doing calculus. A little extra bottom time can put you in a jackpot. If you are going to do it, don't make your plans from advice on the internet.
Bob
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There is no problem that can't be solved with a liberal application of sex, tequila, money, duct tape, or high explosives, not necessarily in that order.
Ime most planning calls that a bounce dive, think of 30 fpm ascent. There is a Shallow stop on software. Sb seems to be anti deep air, but so some of us do it with clear conscious, with proper planning and gas management. Get a good instructor and make your own risk assessment.
Dr. Lecter
Contributor
I like air fine for 200' and even a bit beyond, but that's me and my own experience with narcosis versus ability to function (and to self-monitor for when I'm not on my game even if I feel 'fine'...but we're getting meta here and I don't want to convey this is an exact science... people get narced and die despite previously being 'good at deep air'). Dropping to 200' rather slowly and only staying 5 additional minutes strikes me as pretty pointless, because it's not like you should do it without the gear and gas for a much longer dive.
Why not? Very briefly and not all the reasons why not, you should be assuming something will go wrong and give yourself at least a few minutes of fudge time on the bottom, which will give you a significant deco obligation (I don't have V-Planner or any tables here at work, but last time I was around 190' on air I recall clocking almost 3 additional minutes of ascent time for every additional minute of bottom time with a single lean deco gas). You should also plan for at least one and properly all of your deco mixes to be lost/depleted/inaccessible to you, so you'd want to have enough air on your back to be able to deco out on just that, even including your extra contingency time. That means you're well into doubles territory (just for volume, to say nothing of redundancy) plus at least one stage of deco EAN.
If you're going to 200', you may as well go for a more reasonable amount of time and plan/execute accordingly. Can drop to 200' over 4 minutes, stay for 5, and then do your deco with just an AL80 full of air on your back (and hopefully at least a pony of nitrox for deco)? Maybe, depending on tables and your air consumption rate. But the consequences of something going even slightly wrong when you do that are through the roof, and the chances of that something slightly wrong happening are also elevated.
Tigerman has inspired me to be clearer, even though I generally believe a word to the wise is enough and Darwin take the rest.
Even setting aside things like CO2 retention, oxtox, and what constitutes overexertion being a completely different animal at 200' than even at 130' . . . a simple free flowing second stage at 200' will almost certainly kill you if you're on a single tank of air. You will be narced such that the very best you (or any of us) can hope for is significantly delayed mental reaction time. 'Ah, that's gushing bubbles! <seconds of processing> I know that shouldn't be gushing bubbles! <seconds of processing> I need to fix it! <seconds of processing> <plays with second stage controls>
And by that time, you're probably breathing water. Don't go deep without knowing WTF you're getting into, having the gear you need to survive a worst case scenario, and the traning/experience to operate that gear in that worst case situation... potentially while narced in a way that recreational depths simply doesn't give you any clue exists.
Why not? Very briefly and not all the reasons why not, you should be assuming something will go wrong and give yourself at least a few minutes of fudge time on the bottom, which will give you a significant deco obligation (I don't have V-Planner or any tables here at work, but last time I was around 190' on air I recall clocking almost 3 additional minutes of ascent time for every additional minute of bottom time with a single lean deco gas). You should also plan for at least one and properly all of your deco mixes to be lost/depleted/inaccessible to you, so you'd want to have enough air on your back to be able to deco out on just that, even including your extra contingency time. That means you're well into doubles territory (just for volume, to say nothing of redundancy) plus at least one stage of deco EAN.
If you're going to 200', you may as well go for a more reasonable amount of time and plan/execute accordingly. Can drop to 200' over 4 minutes, stay for 5, and then do your deco with just an AL80 full of air on your back (and hopefully at least a pony of nitrox for deco)? Maybe, depending on tables and your air consumption rate. But the consequences of something going even slightly wrong when you do that are through the roof, and the chances of that something slightly wrong happening are also elevated.
Tigerman has inspired me to be clearer, even though I generally believe a word to the wise is enough and Darwin take the rest.
Even setting aside things like CO2 retention, oxtox, and what constitutes overexertion being a completely different animal at 200' than even at 130' . . . a simple free flowing second stage at 200' will almost certainly kill you if you're on a single tank of air. You will be narced such that the very best you (or any of us) can hope for is significantly delayed mental reaction time. 'Ah, that's gushing bubbles! <seconds of processing> I know that shouldn't be gushing bubbles! <seconds of processing> I need to fix it! <seconds of processing> <plays with second stage controls>
And by that time, you're probably breathing water. Don't go deep without knowing WTF you're getting into, having the gear you need to survive a worst case scenario, and the traning/experience to operate that gear in that worst case situation... potentially while narced in a way that recreational depths simply doesn't give you any clue exists.
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oldschoolto
Contributor
It is not smart to tell a diver with 20+ dives that's it ok to do a bounce dive to 200' on air... It'll be a stupid stunt that he may very well not walk away from... The hit of nitrogen narcoses could very well put him in real danger...... Air is not a very good gas to work with... When there is TRI-MIX... Plus very good divers that can teach you the safe and right way to dive at those depths...
Or Just grab the navy tables... Do a little math and go do it... maybe you'll come back....
Jim...
Dr. Lecter
Contributor
Helium adds additional risks to a novice/self-taught deco diver's dive that experience with just Oxygen/Nitrogen diving won't alert them to, though. Is it safer to tell them to go to 200' on trimix than air? I wouldn't say that's necessarily true. Neither one is going to be particularly safe.
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