Another Deco profile post.

[Remy B.]

i was scratching my head on that too.... Last I checked deep stops were a function of your depth, not an absolute depth. I.e. 75% of your max depth, vs 50%, vs 25% or whatever

confusing isn't it, at sea level are we at 1 Bar gauge or 1 Bar absolute ?

 

[JohnnyC]

Remember this is not about Deep stops, for me deep stops are everything deeper than 12m or 2.2bar absolute, we know that the NEDU study shows that those deep stops will create more quantity and bigger bubbles.

That's not a deep stop.....

 

[Patoux01]

The 21m stop is quite largely accepted for anyone using Nx50. These are deep stops if you ascend from 30m, if you're ascending from 200m, a first stop at 21m might actually be a bit on the shallow side.

Really, take my (our?) advice and go grab that book, it costs 30€, it's available online and as ebook so there's no shipping and waiting whatsoever. It will save you (and participants here) a lot of time. You are clearly very confused about basic deco principles. You could go over your course materials for AN, DP and probably helitrox again, that should help as well (but since that's supposedly what you've already done, i'm not sure what materials you have).

 

[Remy B.]

Go ahead, test it yourself: Subsurface is free

Elmo correct me if I'm wrong but it seams that those heat maps actually have nothing to do with deco algorithms and compartment behavior right ?

Edit: I found it, now I can play with the Heat Maps and GF, I understand better images, it will safe some grief I'm causing with my questions and my confusion.

What do the Yellow represent ? more yellow more heat, is that worse or better

can any body explain me what the Yellow in the Heat map represents ?

 

[lermontov]

No, I understand that tissues are different and they on-gas and off-gas at different rates. ( how much and how fast I don't know )

But will you not reach a pressure equilibrium on the slow tissues at shallower depth where they need a greater pressure to be significant ?, or you still On-gassing dangerously ?

if the Tissue have a determined pressure due to the pressure of atmospheric weight then it will have a greater saturation pressure in the tissue and the only way to Off-gas is by differential pressure, Tissue gas pressure been higher and escaping due to the fact that at that point the ambient pressure have a lower pressure, if it is not like that gas doesn't flow, you need to have gas differential pressure in order for flow to occur or not ?

yes your correct but bear in mind when you see a graph with a line its not a thin line in regard to all tissues compartments its only a line for faster tissues as in fact all the different compartments have their own M value so you may have steep gradient for faster tissues but still a very low gradient for slow ones so in reality if your doing a short shallow dive <35m your might not be off gassing the slow compartment until you get to say 6-7m
keep plugging away at it it will become clearer the more you wrestle with it

 

[Remy B.]

keep plugging away at it it will become clearer the more you wrestle with it

Working on it.

 

[elmo]

The heat bar below have a different color intensity ( yellow glare ) between the two profiles, is that the amount of tension or Bubbles ? to what refers that ?, can I assume the more yellow the color then it is worse correct ?

I'm refering to the GF-45/75 and the modified version of redistributing the stops between 12m-9m and 6m (1st and 2nd heat bars ).

I was actually expecting somebody to modulate these two profiles with a Heat Bar, Thanks a lot.

I've copied the heat map legend from the Subsurface User Manual Subsurface 4.6 User Manual | Subsurface

The manual explains the heat map in some detail. In short, the heat map represents the inert gas pressure in each tissue through the dive. Fastest tissue at the top and slowest at the bottom. The colours represent the rate of on-gassing (cyan to purple) and the instantaneous Buhlmann gradient factor applicable to each tissue when off-gassing (green to red).

 

[Remy B.]

Thanks Elmo, that explains a lot, 1 picture explain more than a 1000 words, it represent efficiency or % off-gassing, if I compare the GF-45/75 to redistributing the time between 12-9-6m you can see the efficiency difference.

To bad that Multi-Deco doesn't have a Heat Map

 

[kensuf]

Wow. This is incredibly basic stuff.

If the partial pressure of the inert gas you are inspiring is greater than the partial pressure of the inert gas that is absorbed in your tissues, you on-gas. If the partial pressure of the inert gas you are inspiring is less than the partial pressure of the inert gas absorbed in your tissues, you off-gas.

Go from sitting on your couch to 1m in a pool while breathing air, you're on-gassing.

Start breathing a bottle of nitrox (anything > fO2 of 21%) while sitting on your couch, you will begin off-gassing.

The rate of on-gassing / off-gassing will be determined by many things, some of them include the partial pressure of the inert gas you're breathing, the tissue saturation, workload, temperature, etc. The greater the partial pressure of inert gas, the greater the rate of absorption. The lower the partial pressure of inert gas, the slower the rate of absorption.

If you stay at 12m during a mandatory staged decompression stop, while breathing 50% nitrox, your rate of off-gassing will be less than if you distributed your stops at 12m, 9m, 6m, and 3m while breathing 50% nitrox. This is because the PN2 at 12m is 1.1, at 9m it is 0.95, at 6m it is 0.8 and at 3m it is 0.65.

It is theoretically possible to do a dive and surface with a lower inert gas load than when you started your dive.

 

[tbone1004]

confusing isn't it, at sea level are we at 1 Bar gauge or 1 Bar absolute ?

that confusion should have been addressed in open water and should not be a point of confusion or discussion in a decompression profiles thread. It is ignored in the deep stops concept which is an issue, but since they've been all but disproven, it shouldn't be much of a discussion anyway