unlimited dives shallower than 30 ft. min S.I.

[Spoon]

Anyway I surfaced feeling kinda tired with a little bit of a headache, did a 2nd dive an hour l8r on another wreck at about 40 feet for 30 minutes. After surfacing from the 2nd dive I felt sooo much better it was like night and day.

Leads me to believe that the time spent shallow on the second time was in essence me offgassing the nitrogen from the second and first dive.

i totally agree with you becasue in my case i was offgassing the remaining nitrogen from dive 4 onwards. thats why i felt relatively better as compared to my routine of three dives in excess of 60ft.

another question? if we are off gassing shallower than 20ft, then it would be relatively safe to do your s.i. underwater? if that was the case it wouldnt be a surface interval more of an offgassing phase whether done at surface or uw am i making sense?

 

[Jamdiver]

Another intertesting question, yes you are making sense.
However this question is over my head , the more knowledgeable members of the board can probably answer that question.

I'm inclined though to think that it'd be better to spend your SI on land than in water. Why? On land you're not loading any additional nitrogen in your system, ~20ft or shallower you are breathing air under pressure and are probably adding additional albeit (very minimal) nitrogen into your system, even though you're offgassing.

Lol, am I making any sense?

 

[Spoon]

I'm inclined though to think that it'd be better to spend your SI on land than in water. Why? On land you're not loading any additional nitrogen in your system, ~20ft or shallower you are breathing air under pressure and are probably adding additional albeit (very minimal) nitrogen into your system, even though you're offgassing.

Lol, am I making any sense?

you are making sense but i am way over my head! lets just wait for the more knowledgeable members to comment. im really curious though

 

[miguel sanz]

saw a show in the discovery channel, "marine machines" they featured a guy who stayed underwater breathing air from a depth of 15 ft for 3 whole days..

IN A DRY SUIT?

 

[Dr Deco]

Hello Spoon:

You can make numerous dives of the type you mention, i.e., less than 30 fsw. There are many commercial divers who search for sea life, e.g., clams and such, who perform dives such as this every day.

Dr Deco :doctor:

 

[chip104]

Hello Spoon:

You can make numerous dives of the type you mention, i.e., less than 30 fsw. There are many commercial divers who search for sea life, e.g., clams and such, who perform dives such as this every day.

Dr Deco :doctor:

yippee!!!





Thanks doc!

 

[kraken]

You might want to surface just to stay hydrated and give your body a chance to warm up.

 

[BarryNL]

guys i know you can basically stay shallower than 30ft without time limits and wanted your opinions or theories f you can do multiple repeated dives over a 12-13 hour period with minimum si? just asking because i did 8 dives last week. only dive 1 to 3 were deeper than 30. if you waited long enough to offgass the nitrogen from dive 1 to 3, then theoretically you can dive onwards with min S.I since you are diving shallower than 30 ft?

The 30ft thing comes from the original Haldane theories that a 2:1 pressure change would not cause decompression sickness - ie. ascending from 2 ATA at 30ft to 1ATA at surface level would always be safe as this pressure differential would not cause bubble formation. More modern research suggests this is not always safe and the "unlimited" diving depth should probably be 15ft, meaning that a 1.5:1 pressure change is always safe.

 

[BarryNL]

Another intertesting question, yes you are making sense.
However this question is over my head , the more knowledgeable members of the board can probably answer that question.

I'm inclined though to think that it'd be better to spend your SI on land than in water. Why? On land you're not loading any additional nitrogen in your system, ~20ft or shallower you are breathing air under pressure and are probably adding additional albeit (very minimal) nitrogen into your system, even though you're offgassing.

Lol, am I making any sense?

You need to understand the half-life type nature of on/off-gassing, which is kind of complex although if you've ever studied radioactive decay, it's the same sort of thing. Basically, the upshot is that if you dive to, say, 40ft for 10 minutes and then ascend to 20ft, then slow tissues like ligaments (long half-life) will still be on-gassing while faster tissues like muscles (short half-life) will be off-gassing.

In other words, yes, spend your SI on land so that ALL tissues are off-gassing.

 

[pipedope]

I have done lots of multi hour dives at between 20 and 30 feet with no problems.

Now if you want to think about offgassing in the water you might look for Pyle's papers on IWR (in water recompression) where he suggests that a significant part of the IWR benefit may be from the 'in water' part even without recompression.
If you are borderline on your stops or borderline on DCI and cannot get to a chamber quicly it may help to remain in the water, just floating at the surface. Breathe O2 if available.
It seems that being supported by the water greatly reduces the likelyhood of bubbles causing damage.

As always this is a gross oversimplification of a complex and controversial subject. It is worth studying the literature and deciding for yourself what youmight do in case of a problem. If you choose to keep IWR as an option then train and equip properly for IWR.