OK to Bounce Dive to 220 Fsw as...

[brockbr]

I know what your trying to say, but a PPO2 of 1.5 is lots of PP to tox. There have been numerous documented cases in the commercial diving industry.

There is another variable in the formula and that's time of exposure. What doesn't hurt you at 10 minutes, can kill you in 2 hours. It's also accumulative with repetitive dives. There are also individual tolerances to PPO2, so there's a good reason for planning a 1.4 PPO2 maximum.

You hit the nail on the head, which is why I made the comment about exposures in my original post.

Based purely on the physiology of an O2 toxicity hit, you would have to be exposed for minutes before any symptoms were felt (based on the lungs reactions to the elevated pO2, and the production of free radicals). Obviously, this all comes down to dosage (amount/time). All this is to say that a pO2 of even something crazy like 4.0 (switching to O2 at 100') would be tolerated if the dosage was low enough (seconds). Just trying to put it into perspective.

 

[carrielsal]

I didn't say in my first post it was. I was just saying what we did. But all in all I think the dive was done safely.

How could this dive have been dove safely if you are are not prepared for a worst case scenario? I wouldn't do this dive with my best dive buddy on a single tank, whether it's and AL80 or steel 95.

Wouldn't that depend on when the problem occured and what the problem was? For instance, if two divers had decended at the beginning of the dive to say around 130 to 140 ft and at that point something happened where the two divers had to share a remaining tank, would an AL80 hold enough air for them to make it back to the surface if they immediately began to accend? (Assuming they are not total air hogs)

2 divers, most likely narc'ed, under stress? What do you think the work load factor would be for something like this? x2 x3?
No....there is not enough air. I, for one, would not bet my life on this or or the life of another diver who is looking at me as a professional. I am sure there are probably hundreds of divers who follow the DM's through the hole with no issue. It's when the sh#% hits the fan that someone will die.

 

[BDSC]

" If you have a catastrophic gas failure at depth requiring an air share at 140ft, wouldn't it be more reasonable to assume there will be greater stress and higher DCR rates than less? I just think it's wiser to consider emergencies in their worst case rather than best case possibilities, let alone probabilities.

I hear ya and good points. So then what is the answer as to how to dive this dive and others like it "safely"? (New or experienced divers) Some would say you could only do this dive safely if you had a pony for another air source. Without it, you would be taking a big risk because just like you said, what if there was a catastrophic failure after 6 or 8 minutes of bottom time. No matter if you are experienced or not, when you're out of air you're out of air!

But this dive is done by probably thousands of divers every year. Some very experienced and some not. If it was really unsafe, wouldn't we be reading on a weekly basis how divers are dying in the Blue Hole? Wouldn't "luck" run out on a more frequent basis than it does? Just how often has anyone ever experienced a catastrophic failure? Not me in over 600 dives nor do I even know of anyone who has ever had this happen. Could it happen? Yes. Likely to ever happen? No.

I guess it really depends on how a person defines "safe" and what they consider to be a reasonable "risk".

 

[DCBC]

The lesson the new divers learned was that diving to 144 ft was no big deal.

Which was the wrong message to give.

 

[BDSC]

I wouldn't do this dive with my best dive buddy on a single tank, whether it's and AL80 or steel 95.

Understood. So for you the risk is too high to do this on a single tank. But for many many people, the risk is an acceptable one and therefore don't view the dive as a unsafe dive or practice.

 

[Blackwood]

Two problems here.

Three, actually. When DCBC is talking to BDSC, I have a really hard time keeping track of who is who.

 

[BDSC]

You mean like this?

YouTube - Scuba Diving Accident Intervention Bahamas 12/04/08

Most folks that I know that have watched this pretty much think it was staged.

 

[carrielsal]

I hear ya and good points. So then what is the answer as to how to dive this dive and others like it "safely"? (New or experienced divers) Some would say you could only do this dive safely if you had a pony for another air source. Without it, you would be taking a big risk because just like you said, what if there was a catastrophic failure after 6 or 8 minutes of bottom time. No matter if you are experienced or not, when you're out of air you're out of air!

But this dive is done by probably thousands of divers every year. Some very experienced and some not. If it was really unsafe, wouldn't we be reading on a weekly basis how divers are dying in the Blue Hole? Wouldn't "luck" run out on a more frequent basis than it does? Just how often has anyone ever experienced a catastrophic failure? Not me in over 600 dives nor do I even know of anyone who has ever had this happen. Could it happen? Yes. Likely to ever happen? No.

I guess it really depends on how a person defines "safe" and what they consider to be a reasonable "risk".

When I was a new diver, I would have been the first one in the water to do this dive. I'm sure there were lots of things we did that we just didn't realize how badly things could go wrong. Luckily for me, nothing ever happened. But, you only have to look at the Misshaps and Accidents forums to find out how something that seems to be small can have deadly consequences.
As with anything else in life, the more I dive and the more experience I gain, the more I find I don't know. Knowing what I know now, there is no way in hell I would lead a dive like this with new divers and no redundancy.

 

[BDSC]

Three, actually. When DCBC is talking to BDSC, I have a really hard time keeping track of who is who.

I even get confused!

 

[carrielsal]

Understood. So for you the risk is too high to do this on a single tank. But for many many people, the risk is an acceptable one and therefore don't view the dive as a unsafe dive or practice.

Isn't ignorance bliss?