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Utrinque Paratus
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Discussion Starter #1
right if you were on a dive to 85 meters on a new wreck 25 minutes into it and you come across a sealed room in the wreck which has air trapped there, big enough area to get out of the water altoghather and sit there, so the question is

a, would you need to do decompression before going into that area

and

b, as it was air from the surface would it be safe to breath and not flip out?

max deapth of air 66 meters

just somthing to play with as i know cave divers have stage tents :)

graham
 

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Team Tricky: Diving with Twins
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milldog said:
a, would you need to do decompression before going into that area
No, the air pocket would be at ambient pressure.
b, as it was air from the surface would it be safe to breath and not flip out?
Probably, not definitely, and certainly not indefinitely.
 

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milldog said:
a, would you need to do decompression before going into that area
No for the same reasons given by Tricky
milldog said:
b, as it was air from the surface would it be safe to breath and not flip out?
Same as tricky because:

The air would be "fresh" as long as you can guarantee that you were the first there. To guarantee the quality after the first breath, each exhalation must remove the breathe from the area - and therefore the volume of the area would reduce by that breathe.

Same as uwila because: the risks and hassles are too great
 

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Utrinque Paratus
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Discussion Starter #7
JonP said:
The ppo2 would be a bit on the high side wouldn't it?

thats what i thought but i might be wrong :)
 

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To add a little detail to my thinking

The air would be at ambient, so no deco needed.

The air would be at ambient, so the ppO2 would be a touch higher than recommended :) if you wish to avoid an O2 hit. Still, if you were totally out of the water, there might be no risk from drowning and I've heard it said that it's not the O2 hit which is dangerous, just the drownig as you fit. So maybe it would be 'interesting' rather than dangerous :D
 

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Buckets thrown overboard while-U-wait
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uwila said:
The air would be at ambient, so no deco needed.

The air would be at ambient, so the ppO2 would be a touch higher than recommended :) if you wish to avoid an O2 hit. Still, if you were totally out of the water, there might be no risk from drowning and I've heard it said that it's not the O2 hit which is dangerous, just the drownig as you fit. So maybe it would be 'interesting' rather than dangerous :D
Unless you bashed your head on the side :)
 

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JonP said:
Unless you bashed your head on the side :)
Very true :) and it might be fairly difficult to 'sober up' and get back out again.

No doubt Graham will let us all know after he's tried it :D
 

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How would you get in if it was sealed and surely once its unsealed wont it fill with water and force the air out? Or am i totally missing the point?

Gareth
 

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Team Tricky: Diving with Twins
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It would have to be sealed on all sides except the bottom. You'd have to swim up in to it.
 

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As in upside cup in the sink with the air forcing the water out?
 

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Don't do it!!!!!!

Never mind that the room has been sealed and not breathed from. The oxygen will be depleted by the oxidisation of the surrounding structure.
Too many people have died in the past after entering void spaces on board ships without flushing the air through first. In one incident three people died because the second went in to rescue the first etc!!!!!!
Dive carefully
Larry
 

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Larry Hadley said:
Never mind that the room has been sealed and not breathed from. The oxygen will be depleted by the oxidisation of the surrounding structure.
Too many people have died in the past after entering void spaces on board ships without flushing the air through first. In one incident three people died because the second went in to rescue the first etc!!!!!!
Dive carefully
Larry
Sounds like standard confined space deaths of old - always in 3s. That's how many you get in the front of a transit.

It's a gas filled space - you don't have a clue if it will support life.

Adrian
 

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Utrinque Paratus
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Discussion Starter #16
i asked the question because you could in theory set up a habitat inside a wreck with a large polythene sheet as the pressure would force against the hull and seal it.

enter from the bottom and work from there on the wreck, flushing the space would be done via surface line and compressor which could be taken in after, it would of course be a short term working environment.

just a thought, i got the idea from the deep blue film and thought if it could be done on a larger scale

Graham
 

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Mark Milburn
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All the above are correct, but, the one thing you missing Milldog is the CO2, you'd start to get a hit as soon as you started inhaling your exhaled gas.

As for the PPO or the PPN it wouldn't bother me as long as I knew what gas it was. If the O2 had been depleted, it would have to be serious depleted to get below 0.16 PPO from a starting point of 1.9!

The other problem is what caused the gas pocket, it could have been gas produced from decaying bodies/munitions/batteries all would be very nasty even at the surface.
 

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milldog said:
i asked the question because you could in theory set up a habitat inside a wreck with a large polythene sheet as the pressure would force against the hull and seal it.

enter from the bottom and work from there on the wreck, flushing the space would be done via surface line and compressor which could be taken in after, it would of course be a short term working environment.

just a thought, i got the idea from the deep blue film and thought if it could be done on a larger scale

Graham
Habitats are filled in the WKPP with Air - about the only tank on the project that is :) Divers resting within them are breathing from their own gas supplies - the air provides only room to eat, switch regs - as well as get the diver clear of the water which is known to reduce the likelihood of CNS tox and (almost as importantly) get them warm.
 

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milldog said:
right if you were on a dive to 85 meters on a new wreck 25 minutes into it and you come across a sealed room in the wreck which has air trapped there, big enough area to get out of the water altoghather and sit there, so the question is

a, would you need to do decompression before going into that area
No because - as others have stated - the air trapped inside the wreck would be at ambient pressure unless, of course, it's sealed inside a totally water-tight bulk head. The problem there is that unless there's an intermediate air lock that allows you to balance the pressure difference, opening the door into the air-tight area would cause water to rush in!

milldog said:
b, as it was air from the surface would it be safe to breath and not flip out?
I don't honestly think that oxtox would be the problem here and anyway, why would getting an oxygen hit be a problem in a dry environment? Don't forget that the bit that kills you with an oxtox incident is usually not the oxygen hit itself - it's the fact that you usually spit out your reg and drown!

The other thing to consider is that the inside of the wreck is probably a) made of metal and b) damp so my guess is that the oxygen content of the air would actually drop over a long period of time as the oxygen reacts with the metal, causing corrosion. This is part of the reason why some training agencies used to warn divers to be careful about leaving fills in cylinders for long periods of time - if the cylinder contained any entrained water vapour, it was believed that it could cause a drop in the oxygen content of the gas inside the cylinder due to a corrosive reaction with the metal walls of the cylinder. In truth, the drop in oxygen contact is so small that it'll hardly register. For a wreck that may have been down there for a long period of time, though, it's a possibility, I guess.

Then, of course - as others have alluded to - you've got the problem of CO2 build up. Each time you breathe out into that environment, you're increasing the CO2 content which is going to continue to rise unless it's artificially 'scrubbed' using a scrubber like those found in a submarine or, for that matter, a rebreather. As Okeanos stated, there's also the other noxious gases to worry about - all that gas that's given off by decomposition/chemical reaction has to go somewhere! Yuk! ;)
 
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