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Re: Re: Safer????


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Posted by MHK on June 22, 2006 at 12:12:20:

In Reply to: Re: Safer???? posted by msblucow on June 22, 2006 at 11:45:48:

Marta,

I believe the sensible way to deconstruct the dive analysis for a dive site such as Osborne is to look at it from a practical perspective. In other words, absent a relative minor potion of the site, the vast majority of Osborne is in the 150'+ range. Certainly no meaningful diving takes place in the 100' range and at best you're looking at a 120'+ dive. I'm unaware of any credible tables that provide for any meaningful bottom time using air in the 150' range, so in order to approach this dive sensibly you are looking at a decompression dive. I'm hard pressed to believe any serious diver would go through the time, effort, expense or trouble to do a dive to 150' that may provide for only a couple of minutes of NDL time. Accordingly, in order for a dive of this magnitude to make any reasonable sense you would want to spend 20 or 30 minutes, maybe more for your efforts..

Naturally that kind of bottom time mandates decompression; once you accept that premise then it begs the questions that if you are going to be at those depths why not use the proper gas? Why not approach this in the safest manner possible? Why not address things such as gas density, narcosis, C02 retention, deep stops, decompression gases, etc. etc?? The better ways to ask the question is what does diving deep on air bring to the table? How is accepting added narcosis, greater gas density, additional C02 retention a wiser course of action?

I realize that many suggest along the lines of " I have been doing deep dives like this for X number of years.." to which I always ask "so what?" Just because, prior to the introduction of Trimix to the general diving population, people dove deep on air does that mean they should ignore advances more currently available in favor of antiquated methods?

Lastly, I would like to point out that I'm not attempting to change the way anyone dives. I'm simply trying to spur a discussion, using a current dive where no one was hurt, to illustrate a point. More often then not no one pays attention to discussions of this nature until a dive accident occurs. Then the usual discussion points of:

1) You don't know the facts;
2) Keep silent out of respect for the family

Or something else along that line sidetracks the salient discussion. In the instant case, we have a long standing club that did an advanced site, without incident, so why not proactively analyze the possible ways to do it safer going forward?

Regards,



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