Any downside to extending the safety stop?

[PfcAJ]

At 15FSW?? No effect, not even a little. The body is releasing nitrogen at that depth not absorbing it. I don't even take my PDC if I'm diving above 30FSW and I don't do a SS for a dive above 30FSW; the whole dive was a SS.

Parts of the body are off gassing. Not all.

The he fastest elimination of n2 is on the surface.

 

[Drin]

Parts of the body are off gassing. Not all.

As long as the tissue pressure of N2 is above the ambient pressure of N2 the tissue will be offgassing. This will continue until the tissues reach equilibrium with the ambient pressure. Poorly perfused tissues will diffuse gas back into the bloodstream more slowly during offgassing but they will still offgas.

-Adrian

 

[PfcAJ]

Depends on how much inert gas that slow tissue has absorbed. On a short dive, that's not much.

 

[Drin]

Depends on how much inert gas that slow tissue has absorbed. On a short dive, that's not much.

My statement still holds true. As long as the tissue pressure is above ambient pressure offgassing will occur.

-Adrian

 

[PfcAJ]

indeed it does.

 

[Michael Guerrero]

I am having trouble finding it but DAN did a report that 5 minutes is a good time because it takes about 5 minutes for your blood to be circulated though your body, this causes much more offgasing than a 3 minute stop.

It's more like a minute or two for blood to circulate through the body.

To answer the question, it won't hurt you from a DCI perspective to do this. It's like doing a deco stop at 10' for a long time. The nitrogen in your body is under more pressure than at the surface to there will be less bubbling than on the surface.

For recreational dives it probably doesn't matter that much. I usually do a stop at 20' for 2 min, then 15' or 10' for 3 min.

 

[Ricky B]

Research in the US has shown that the type of safety stop has quite a significant impact on bubble presence and formation post dive. The optimum was found to be 1 min at 6 metres and 4 min at 3 metres.

Results were staggering in that this stop resulted in all bubbles being gone within 45 minutes and that upon surfacing, this group had less bubbles in their system than a group that did 2 mins at three metres had an hour later!

(Even more staggering was that the group that did no safety stop had more bubbles in their system after two hours than the initial group had upon surfacing!)
...
[source: Deco for Divers – Mark Powell]

Yet the standard recommendation is to stay below the 10-ft ceiling to avoid inadvertently going above it, which results in a 15 feet safety stop being considered ideal.

Is that because the conventional wisdom has not caught up to the results of the most current research, or are the results of that research merely indicative but not sufficiently definitive to change the conventional wisdom?

 

[Jack Hammer]

I believe the 15' recommendation stems from many OW divers lacking the buoyancy control to maintain a specific depth for 3-5 minutes. Splitting the difference between 10' - 20' gives newer divers a 15' stop with the largest margin for error up or down and staying between the current minimum and maximum recommended depths for that stop.

 

[SADS 669]

I believe the 15' recommendation stems from many OW divers lacking the buoyancy control to maintain a specific depth for 3-5 minutes. Splitting the difference between 10' - 20' gives newer divers a 15' stop with the largest margin for error up or down and staying between the current minimum and maximum recommended depths for that stop.

In my experience even though staying at 20 to 15 ft for longer than 5 minutes is ok, and not really an issue one way or the other. In my opinion it is vital to do some time at deeper depths ie half the depth of your max on a deep dive, say 150 ft then a minute at 75 is very important and if you have completed a 100 ft dive a minute ( or two) at 60 ft is very beneficial. Then you can do the 30 ft 20 ft and 10 ft to ensure a safe ascent

 

[halocline]

In my experience even though staying at 20 to 15 ft for longer than 5 minutes is ok, and not really an issue one way or the other. In my opinion it is vital to do some time at deeper depths ie half the depth of your max on a deep dive, say 150 ft then a minute at 75 is very important and if you have completed a 100 ft dive a minute ( or two) at 60 ft is very beneficial. Then you can do the 30 ft 20 ft and 10 ft to ensure a safe ascent

What are you basing this opinion on? Some study or evidence, or is it just what you think? And 'vital' is a pretty strong word.

I read in the PADI encyclopedia of recreational diving that there is some evidence that an extended safety stop is particularly effective at off-gassing in NDL profiles. I do know that I personally feel less fatigued after doing longer stops; I usually spend 5-10 minutes total at 10-15 feet, depending on the dive and conditions.