Why do people add a few minutes to their last deco stop?

[boulderjohn]

You have a cite for that? All I heard was bubble size control, and, well, we know how that bubble thing went...

I'm having trouble understanding what you are asking for. I must be missing something. Are you asking him to cite evidence that when you are hanging out above 20 feet, all your tissues are either off-gassing to a level that is safe to surface, or they are on-gassing to a maximum pressure that cannot exceed a level that would be safe to surface? Isn't that what you yourself just wrote?

 

[L13]

I.e. no cite. Got it. Moving along.

Yes, those who believe it is all random magic should just move along.

 

[L13]

I'm having trouble understanding what you are asking for. I must be missing something. Are you asking him to cite evidence that when you are hanging out above 20 feet, all your tissues are either off-gassing to a level that is safe to surface, or they are on-gassing to a maximum pressure that cannot exceed a level that would be safe to surface? Isn't that what you yourself just wrote?

And, the tissues that are off gassing are in a safer condition (lower supersaturation) while they are off gassing while having little or no(if on 100% O2) reduction in off gassing rate. And bubbles that do exist won't expand as much.

If you believe that supersaturation or bubbles have anything to do with DCS, it is obvious to everyone except the magicians.

 

[dmaziuk]

I'm having trouble understanding what you are asking for. I must be missing something. Are you asking him to cite evidence that when you are hanging out above 20 feet, all your tissues are either off-gassing to a level that is safe to surface, or they are on-gassing to a maximum pressure that cannot exceed a level that would be safe to surface? Isn't that what you yourself just wrote?

This:

It's even better than that. There is a significant advantage to spending more time in that zone DCS-wise than surfacing immediately. As long as other factors don't drive a quicker surface.

Where's the significant advantage coming from and what other factors? That is the studies I'd like to see.

What I wrote is the only theory I know of is that bubbles are smaller at 3..6 msw than at the surface and therefore will pass through cellular membranes easier, leading to faster elimination. AFAIK it is as valid as the rest of the bubble theories.

 

[crofrog]

It's even better than that. There is a significant advantage to spending more time in that zone DCS-wise than surfacing immediately. As long as other factors don't drive a quicker surface.

Let's say we have a typical-ish techincal dive.

150ft on 21/35 for 30 minutes, nitrox 50 for deco.

Using whatever GFs (or model) you want, what is the pDCS?
If you extend whatever stop you want by however long you want, what is the pDCS?

 

[L13]

Where's the significant advantage coming from and what other factors? That is the studies I'd like to see.

You don't need studies. it is basic physics and chemistry.

Just one (of many) examples: Supersaturation is less at 6 msw than it would be on the surface. If you believe that supersaturation has anything to DCS that means you are safer. Meanwhile, if you are breathing EAN or O2, the pressure gradient is higher removing inert gas from your system faster than if you were breathing air on the surface. Ie. you are safer, and decompressing faster.

etc.

There are many basic physics and chemistry reasons why deco at depth is safer and more effective than deco on the surface, as long as you aren't deep enough to result in on gassing of slow tissues to dangerous levels.

What I wrote is the only theory I know of is that bubbles are smaller at 3..6 msw than at the surface and therefore will pass through cellular membranes easier, leading to faster elimination. AFAIK it is as valid as the rest of the bubble theories.

While theories like that would further mitigate with the problem of bubbles, they are far from the only advantages to extending shallow deco, particularly at higher FO2.

 

[L13]

Let's say we have a typical-ish techincal dive.

150ft on 21/35 for 30 minutes, nitrox 50 for deco.

Using whatever GFs (or model) you want, what is the pDCS?
If you extend whatever stop you want by however long you want, what is the pDCS?

do the exact numbers really mater? There is no question that pDCS case 2 < pDCS case 1.

If GF's are high (or for other models, less conservative) the PDCS case 2 even more < pDCS case 1 than it would be if using whatever model more conservatively.

But, if you believe this isn't true, why do you use any of those models? Just dive and surface however you feel like, if it is all random magic anyway it shouldn't matter.

 

[crofrog]

do the exact numbers really mater? There is no question that pDCS case 2 < pDCS case 1.

If GF's are high (or for other models, less conservative) the PDCS case 2 even more < pDCS case 1 than it would be if using whatever model more conservatively.

But, if you believe this isn't true, why do you use any of those models? Just dive and surface however you feel like, if it is all random magic anyway it shouldn't matter.

You said it conveyed a significant advantage. I think the numbers are pretty important if you want to talk about either statistical or practical significance.

 

[L13]

You said it conveyed a significant advantage. I think the numbers are pretty important if you want to talk about either statistical or practical significance.

If you want to prove it is insignificant, provide cites or numbers to back up your argument.

Can you cite any research or numbers that show that it isn't significant? See, two can play that "give me cites or exact answers, or you are wrong" game.

Tell you what, even if you don't have the cites or numbers, present a physical explanation consistent with known physics, chemistry and physiology, that could even slightly possibly suggest different, and I will take you seriously enough to go back and re-find the research and give you cites.

Otherwise, go sit in the corner with the other magicians that say that since someone doesn't have a cite memorized, they must be wrong. Keep believing the world is magical and random and we know nothing about it, just because we don't know everything about it.

 

[VikingDives]

Otherwise, go sit in the corner with the other magicians that say that since someone doesn't have a cite memorized, they must be wrong. Keep believing the world is magical and random and we know nothing about it, just because we don't know everything about it.

Magnets, how do they work?