nitrogen nightmare?????

[PacNWdiver]

That's my story, and I'm sticking to it.

Well... You are entitled to your opinion. Just like most things in diving, I suppose it comes down to your own level of acceptable risk. But, I thinks it's important to highlight what she said:

"There is no evidence that recreational free diving on a surface
interval
increases the risk of DCS without additional Nitrogen exposure from
later dives."

There is no evidence. In other words there is no empirical study or other information to support a conclusion either way. Only anecdote and theory. That's all I'm saying. I try not to pass off as fact what is theory or personal assumptions. My assumption is that free diving after a dive with no plans for subsequent dives does not put me at any greater risk of AGE or DCS. And, there is no evidence to suggest I'm wrong.

 

[lamont]

Well... You are entitled to your opinion. Just like most things in diving, I suppose it comes down to your own level of acceptable risk. But, I thinks it's important to highlight what she said:

"There is no evidence that recreational free diving on a surface
interval
increases the risk of DCS without additional Nitrogen exposure from
later dives."

There is no evidence. In other words there is no empirical study or other information to support a conclusion either way. Only anecdote and theory. That's all I'm saying. I try not to pass off as fact what is theory or personal assumptions. My assumption is that free diving after a dive with no plans for subsequent dives does not put me at any greater risk of AGE or DCS. And, there is no evidence to suggest I'm wrong.

You need to read the link that I posted earlier:

http://www.wkpp.org/articles/Decompression/why_we_do_not_bounce_dive_after_diving.htm

Yes, that is all 'anecdotal', but I'm inclined to believe that what they experienced in the WKPP with post-diving bounce dives producing DCS to be a real experience. It isn't a single anecdote, but a repeated observation by the WKPP. To me, that constitutes 'evidence'. Given the WKPPs track record of being at the forefront of decompression theory and
having the theoreticians playing catch-up, I'm inclined to give them the benefit of the doubt.

Plus it is simply plausible. We know that PFOs increase risk of DCS. That implies that the lung do act as a filter. It also implies that single phase models are insufficient to explain DCS -- PFOs don't increase risk if your physiological model is Haldanian. That makes the Haldanian explanation that DAN gave incomplete. We know experimentally that it is incomplete because of deep stops and PFOs and the acceptance of dual-phase models. The fact that DAN's explanation is incomplete isn't a personal assumption.

I think that you are putting yourself at substantially greater risk than you think you are, based on an outdated physiological model of decompression and some surprisingly bad advice from someone at DAN.

 

[derwoodwithasherwood]

It is not for [us] to decide what someones safety level should be, it is for them to decide, and we can help them make good decisions by mentoring and advising, or we can indignantly and self righteously criticize them..

Hear, hear.

 

[PacNWdiver]

lamont,

I have read that article and I'm very familiar with Geoge and WKPP. He is talking about the practice of bounce diving on scuba in caves (to retrieve stage cyliders and the like). He is also talking about long decompression dives. I realize the point about the lungs being a filter for bubbles is what you are trying to make. I'm just not convinced it's as big an issue in the context of the origonal post of this thread. And, I don't think the article you referenced is really applicable becase the context is completely different.

 

[lamont]

lamont,

I have read that article and I'm very familiar with Geoge and WKPP. He is talking about the practice of bounce diving on scuba in caves (to retrieve stage cyliders and the like). He is also talking about long decompression dives. I realize the point about the lungs being a filter for bubbles is what you are trying to make. I'm just not convinced it's as big an issue in the context of the origonal post of this thread. And, I don't think the article you referenced is really applicable becase the context is completely different.

Short air NDL dives may actually be worse than long deco dives in terms of the shower of bubbles that you get when you come up the last 10 feet.

 

[craysea]

hi there everyone, I think i might have opened up a real nasty can of worms here. Firstly we aren't all suicidual divers over here and we do place a value on our lives. Secondly the amount of air you choose to leave in your tank/s is entirally up to the individual. Thirdly we are only talking about ten-fifteen feet of water after a single tank dive. All I were asking was a straight forward question (not being a TROLL) and were hoping to get a simple answer from more experienced divers. This has ended up a debate and has left me wondering if anybody really knows at all. The only thing i can decide on (being a newbie and all) is that if i take down marker buoys when scubaring I can always return at a later stage with more oxygen. But the question still remains the same for anyone whom is unclear on the appropiate nitrogen calculations. I think that it may be safe to say that everyone agrees to be unsure until there is further research into the subject.

 

[DandyDon]

I always prefer to be Mr Nice Guy here. But posts like this tend to set me off....

Hi there Dan I'm in New Zealand so you wouldn't be the one having to rescue
me from myself. I only suck them dry if I can still safety surface eg under 5 metres. Me and my mate are very confident with our own abilities and usually are sob. The worry about having a tank fail due to stress fractures or corrousion are things that don't worry me (they are replaceable). I'm just a very addicted diver whom can't get enough.

Anyway, focus on safety margins, will ya', and post some more with us around the forums.

 

[Christi]

...Secondly the amount of air you choose to leave in your tank/s is entirally up to the individual...

Yes, technically you are correct. If they are your own personal tanks, I guess you don't mind if you suck them dry and they corrode and get water inside. If they are rental tanks, you owe it to the shop and to the next diver to be responsible with the tanks and not suck them dry...compromising the inspection and safety of the cylinder.

 

[craysea]

Yes I do own all my own tanks, but when I rent or borrow other peoples I will always leave 50 bar in them. Also when I suck my tanks dry as stated it is only in shallower waters then an controlled emergeny decent is used. Being mainly a shore diver and also a sod I feel that there really are no risks and the controlled emergency decent is a skill that should be practised more often rather than the once when learning scuba so you can be more confident when the real need (like gear failure) happens and to not panic.