If you see it as a marketing ploy then you don't understand how limiting penetration gas is used as a safety factor. That's been explained by several people so far.
Cave Certs Expiration
- Thread starter MyronGanes
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What is happening here is difficult to explain, and as I type, I am not sure how I can say it so I will not be misunderstood. I will probably fail.
The problem expressed by others with using a strict rule of thirds is that if a catastrophic gas loss were to occur at the moment a dive was turned, the divers would not have enough gas to exit. That is true. There has not been an example of this in history, at least as far as I know. That, too, is true. That is because a catastrophic gas loss is extremely rare to begin with, and the odds against it happening at that time are astronomical.
A lot of people would shrug and say that the odds against it happening are such that it is a risk they are willing to take. There are many risks in cave diving. We try to eliminate as many as we can, but we have to accept some. For example, there is always an unavoidable risk that when you try to exit, you will find that a cave-in has blocked your path, and you can't get out. I don't know how to calculate those odds in comparison to a catastrophic gas loss at the moment a dive is turned, but I do know it has happened at least once.
The book Diver Down describes real dive accidents and discusses the lessons to be learned. One of them is a cave diving accident. The diver in this case routinely argued that the rule of thirds could be ignored in high flow caves because your exit will be so much faster than your entrance. It especially made sense to him while diving solo, since he would not have to worry about a buddy's loss of gas. He made that argument openly to others. It worked great fro him until it didn't, and a roll of the dice on one dive meant that an unlikely sequence of events meant he did not have enough gas to exit.
Everyone has to have a realistic sense of the risks involved in the decisions they make, knowing that they will have to live--or not live--with the consequences of that decision should the odds not work out as expected. For most, violating the rule of thirds on the belief that flow will carry you out is going too far, but following the rule of thirds precisely in a low flow situation is acceptable.
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@syntaxerrorsix same coin... different side.... you are saying manage by policy, I'm saying let the divers manage themselves...
So why is everyone SO against the rule of 3rds across the board?? By the way, think that was a great explanation... and That guy was an idiot... you should always be more conservative when diving TRUE solo... yes I know I said I consider all dives solo but if you have a dive buddy available they are THEN a resource.
I knew I'd win you over.... Ok I also know I did not actually win you over. IT is all about self policing anyway... I just think training standards should be the same across the board.
We have to remember that a buddy's catastrophic gas loss is not the only reason to limit gas use on penetration. There are other problems you may need to solve, and those solutions require time. Losing the line in a siltout is a serious problem, and you will need enough time to find that line. You get that time from your gas.
Let's say you were diving thirds on a single AL 80 at about 100 feet. To keep the math simple, let's assume you had a 0.5 SAC rate going in, but during the emergency you double it to 1.0 cubic feet per minute, meaning you are using about 4 cubic feet per minute on the dive. In that case, you have about 7 minutes to find that line and get out--if you are able to get your breathing down to a calm level immediately after you do. I would not do it with any level of certification.
Let's say you were diving thirds on a single AL 80 at about 100 feet. To keep the math simple, let's assume you had a 0.5 SAC rate going in, but during the emergency you double it to 1.0 cubic feet per minute, meaning you are using about 4 cubic feet per minute on the dive. In that case, you have about 7 minutes to find that line and get out--if you are able to get your breathing down to a calm level immediately after you do. I would not do it with any level of certification.
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Well that's not going to happen. Not any more likely that everyone choosing the same politicians. People believe different things.
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