deco stop question

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KG4PVO

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I cant see a problem with it (if you have enough air too do it , but thought I would ask)

now this is just an example , hypothetical situation

Let us say you are diving to 100 feet on air (1st dive){ you have 20 min on the table}
after 15 min you start your assent and you stop at 50 feet for 15 min then ascend to your safety stop and stop there for 20 min before surfacing



Now my question : is there any problem or negative affects to stopping at a deco stop for too long (ex:2x the recommended time) amount of air permitted

thank s all for your help and input
 
Slow tissues will continue to on gas during the deeper stops. Probaly not an issue for the profile you gave but if you had stops every 10 feet starting at say 130 feet and you doubled each one it would effect your deco times during your shallower stops as your tissues are on gassing inert gas during the deeper stops.
 
You are describing a multilevel dive not one necessarily requiring a deco stop.

A dive computer will take care of the required computation giving you no decompression time at your current depth taking into account the dive profile that has already occurred.

You can preplan a multilevel dive using tables, but you must strictly adhere to the planned profile for it to mean anything. Doing the deepest part of a dive first is a good idea. Stopping at intermediate levels on a deep dive is a good idea, but is not required on a recreational dive. You can find a lot of discussion on this by searching the forum for "deep stops".

Recreational dive is not deco diving. You should not be doing a dive that will incur a deco obligation without the special training and the equipment to make it safe.

You might want to review your course materials on dive planning.
 
Now my question : is there any problem or negative affects to stopping at a deco stop for too long (ex:2x the recommended time) amount of air permitted

Depends how deep it is.

You could stay at 20 feet all day without a problem. Stay at 50 feet too long though and you will be adding nitrogen and going deeper into deco.

Deco software such as V planner is a good way to play around with multi level profiles. Even works for recreational dives!
 
I cant see a problem with it (if you have enough air too do it , but thought I would ask)

now this is just an example , hypothetical situation

Let us say you are diving to 100 feet on air (1st dive){ you have 20 min on the table}
after 15 min you start your assent and you stop at 50 feet for 15 min then ascend to your safety stop and stop there for 20 min before surfacing

Now my question : is there any problem or negative affects to stopping at a deco stop for too long (ex:2x the recommended time) amount of air permitted

thank s all for your help and input

All that tissue stuff the guys were talking about -- some parts of your body on-gas (absorb N2) slower or faster than other parts.

What the guys meant, was that you are not actually off-gassing (in total) when you hang at 50 feet for 15 minutes. You are still absorbing N2.

What some divers do is to practice deep stops - 2 minutes at one-half of your depth. Then rise up to your 3-min safety stop.

So, yes, any stop below 30 feet for too long will probably cause you to continue to absorb N2.

If you need more info then that, then you need to get more training. :wink:
 
There is one problem. That is that you are delaying the start of your SI where off-gassing will be more efficient. If you are planning a subsequent dive, you will either have to delay or reduce that dive. If you are diving with other divers, you will also be delaying or additionally limiting their subsequent dive. There can be a downside to excessive risk reduction.

BTW, in early dives, you may well still be on-gassing slower compartments even at a 15 ft rest stop. But that on-gassing will stop well before you can overload any tissue at such a shallow depth. But it may still have a limiting effect on subsequent dives.
 
There's no issue with adding a 'safety stop' at the end of a 'deco stop'. Do your deco as demanded by your dive planning on tables/computer, then add any desirable safety margin by extending your last (shallow) stop beyond the calculated amount.

It's important to realize that the 'deco stop' remains mandatory, but the 'safety stop' can be aborted if other factors make that more desirable.

Negative factors associated with voluntarily extending stops, beyond the mandatory amount could include:

1) Risk of dislocation from surface support. Current moves you further from your dive boat etc.

2) Cold / Hypothermia. Long periods of relative immobility can cause the diver to get cold. This also has a bearing on off-gassing efficiency.

3) Boredom. Yep, it's not great to be bored for no reason.

4) Reduces response flexibility. Should other divers have problems etc, you will delay boat movement by remaining underwater.
 
ok thanks
so if you stay at a stop point too long you effectively surpass the reason for the stop and ADD to the nitrogen in your body
so this COULD be a bad thing
I can see that
thank you all
just curious
 
In accordance with the Haldanean approach, that you can reduce pressure by 1/2 without negative consequences (actually, it isn't 1/2, it's 1/1.58, but for the purposes of what I'm going to say, it's essentially a wash), you can spend as much time as you have gas, between 30 feet and the surface.

Deeper than 30 feet, and you have to know which compartment is controlling, and what that compartment is doing at the depth where you want to stop. Honestly, this is one of the best features of dive computers -- the computer is capable of the iterative calculation necessary to tell you if your decompression status is improving or worsening where you are. I think one could generally suggest that, if you are 2 ATA above your max depth, it's likely that you are net offgassing for at least a few minutes. If you are deeper than that, you are probably net ongassing, and increasing your total decompression obligation. (Note that there are people who teach this differently -- and one should never plan one's deco based on what someone on the internet has rather vaguely said.)
 
......Let us say you are diving to 100 feet on air (1st dive){ you have 20 min on the table}
after 15 min you start your assent and you stop at 50 feet for 15 min then ascend to your safety stop and stop there for 20 min before surfacing
Now my question : is there any problem or negative affects to stopping at a deco stop for too long.....
Here a graphical view of your hypothetical dive:

In image 1 you just reached the 50ft stop and the first 3 compartments are offgassing, but all the other are still ongassing. N2 loading is at 97%

kg4pv0_1.jpg


In image 2 you have completed the 50ft stop and the compartments in the middle have increased substantially as they are still ongassing. N2 loading is still at 93%


kg4pv0_2b.jpg


In image 3 you can see that the (very long) safety stop at 15ft as reducing quite a bit your N2 loading in the fast and mid compartments. N2 loading is now 76%

kg4pv0_3.jpg

Simulation of this plan (using ZH-L16C - Moderate Conservatism) is here

Alberto (aka eDiver)



 
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