speaking of mantras, i heard of a good one for deep divers... Nitrogen Narcosis is for Christmas, Oxygen Toxicity is for Life.....
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speaking of mantras, i heard of a good one for deep divers... Nitrogen Narcosis is for Christmas, Oxygen Toxicity is for Life.....
It is a method when diving Tables to determine your your max depth and time. Then use your no deco time which was pre-determined from your dive plan and on the way in use EITHER 1/3 of your air supply in OR 1/3 of your no-deco time WHICHEVER comes first.Quote:
Originally Posted by Slüdge
IF you turn on pressure or if you turn on time either way you start your exit which now gives you 1/3 for your exit and leaves 1/3 for emergencies.
For example on an Open Water Dive you are diving to 60' for 50 minutes. You are wearing a single tank AL 80 with 3000 psi
You would use EITHER 1000 psi or 1/3 of your no-deco time say 16 minutes. You would swim into the current and at 2000 psi signal to your buddy and return to your point of entrance (ie shore, anchor line, etc)
This would allow you the same amount of time and air to reach your point of exit.
If an emergency occurred yould would have 1/3 of your no-deco time as well as 1/3 of your air to deal with this emergency.
I suggest this method to new dive students who are using dive tables and analog SPG's. It is a very conservative approach and a means for a new diver to use as`a method to be able to pre-plan the dive ahead of time and to reduce task loading. It is used in conjunction when I am teaching dive planning and tables therefore my explaination does not go into all of the details that would normally be presented.
Hope this helps
I have never heard of using this method in an overhead environment but some may find it helpful.
Andrew and I were going back and forth a little and thought we should post some of our exchanges. To answer his post in response to my initial post I would say the following:
1. I totally agree with Andrew that 1/3rds do not give one sufficient reserve in no-flow caves, and that subtracting a 100 psi off one's calculated 1/3rds is an excellent idea, effectively giving one a cushion of 300 psi.
Fortunately, for those diving in Florida and getting cave fills this is less of an issue. This is because N2 and O2 are not infinitely compressible, with the result that the relationship between cubic feet of gas and psi is no longer linear above 3000 psi (as is easily verified by going to the divegearexpress web site and checking the cubic feet that corresponds to 2640, 3000 and 3440 psi for the different tanks). Lets say you have a 3600 psi fill in double 104s. The total amount of gas for the 1st 1/3rd (from 3600 to 2400 psi) is 80 cuft but the amount of gas for the 2nd and 3rd 1/3rds (from 2400 to 1200 psi and from 1200 psi to 0 psi) is 94 cuft, giving one an additional cushion of 28 cuft (94*2 - 80*2; equivalent to about 350 psi in the linear range). Now lets say you start off with 3500 psi, and round 1/3rds down to 1100 psi, then one fares even better: the 1st 1/3rd (from 3500 to 2400 psi) has 75 cubic feet of gas, the 2nd 1/3rd (2400 to 1300 psi) has 87 cuft, and the remaining third and a bit (1300 psi to 0 psi) has 102 cuft, so the total additional cushion is now 39 cuft (87+102 - (75*2); equivalent to about 500 psi).
For those, however, diving in Mexico with regular Al80 fills to 3000 psi, they don't have
that cushion, and I would certainly agree that in that case on should absolutely take 100 psi at a minimum off one's 1/3rds. (Of course it doesn't hurt to take a 100 psi off 1/3rds for cave-filled steel tanks, and just adopt this as a standard rule/guideline for no-flow caves).
2. Obviously syphons require special gas management considerations (as for that matter does diving with a DPV) and 1/3rds no longer work. I believe this is covered explicitly in the NACD cave book (as well as the GUE one).
3. I'm well aware that the majority of divers don't put a primary in the Ear or even the Eye. Personally, I always do because I like the challenge, especially carrying a lot of stuff and towing a scooter. But the bottom line is that most people don't do it because either (a) they are lazy, (b) it consumes too much gas (because they don't have practice and it is difficult at the beginning), or (c) it takes too much time. But, one only needs to do it once for a series of dives. Clearly, however, too many primary lines, especially if they are not well laid, would be a potential hazard, and I think one could use that as a very good argument to bring the Gold line out into open water. (I'm really not sure why this hasn't been done since an untrained diver could follow a primary line into the cave just as easily as a Gold line running to open water).
4. With respect to Bruce's accident it is impossible to determine the exact causality, because the only person who knows what actually happened is no longer there to provide the answers. Further, the forensic evidence is usually not very helpful (e.g. an autopsy that reports death by drowning doesn't tell us anything we don't already know). That being said I don't think my "Labyrinthine" scenario is very far from the truth. For sure, we do know that Bruce went into Harry's crack with a blind jump, he created a silt cloud such that his buddy didn't feel comfortable following, leading to buddy separation, and finally Bruce must have emerged from the Crack since he was found 400 ft up the Hill 400 with no gas left.
While not putting in jump reels was in all likelihood not the only cause, because clearly a whole bunch of things cascaded and went wrong, it sure didn't help. There is no doubt in my mind that the failure to run a reel/spool from the Gold line to the line in Harry's Crack together with the failure to follow standard protocol associated with placing jumps lead directly to buddy separation, which in turn probably triggered a series of unforeseen events that lead to the accident.
It doesn't appear to me that this conclusion is intellectually lazy and intrinsically unscientific, particularly as one can't very well follow the rigors of the scientific process, when there is so little information available. In such instances, all one can do is make reasonable guesses.
What I was also saying in my post is that if something does go wrong, having one less thing to worry or think about is likely to be very helpful in a close and stressful situation. I remember a very well known cave diver telling me that on one dive he suddenly felt super-nauseous way back in the Berman room and thought he was going to pass out; according to his account he really had to concentrate with all his might to make it out. Fortunately, all he had to do was follow the Gold line. Just think if he'd have had to make several visual jumps on the way out when he wasn't altogether there and partially incapacitated (even though he knew the cave like the back of his hand). For sure it would have made things a lot more difficult.
Bottom line, scientific or not, I've got no doubt in my mind at least that not laying jump lines was contributory towards this accident on all sorts of levels (including situational awareness, following proper protocol and not getting separated, etc.. etc....).
5. Finally, I would disagree that innovation necessarily involves going beyond one's training, at least as far as extreme sports are concerned. Whether you're talking about Ed Vuisters and climbing all the Himalaya peaks without O2, the WKKP crowd or Steve Bogaerts, they don't simply jump right to their record breaking endeavors, but build up rather slowly. (And while Steve Bogaerts is no doubt an incredible diver with a large number of major accomplishments, I don't think that the development of the Razor would count, in my mind, as diving beyond one's expertise). Likewise, I don't think that Forrest's home built rebreather involves diving beyond his training, but I would hope that Forrest tested it out in the pool and then in some simple open water environment, before taking it into a cave.
Marius
...and my (edited) answers:
1) Marius, as I said to you, your point about real gas laws is a really cool point that I'd never thought of. But it's an accident (in the sense that most people have no idea that moving into the non-linear region of the gas laws is saving their butts... and would be unable to explain why even after you finish drawing a bunch of graphs for them), and having peoples' safety depend on that accident seems problematic to me. furthermore, as you point out, it doesn't work so well in Mexico with 3000 psi fills... which has a lot of no flow caves... since the compressibility of N2 and O2 is still pretty linear there.
2) and 3) I agree on.
4) There's a fair chance that this case may have been worsened by not laying spools. But we're all guessing. ANd my concern is that we become lazy, say "Broke rule 2... let's move on", and don't learn as a result. THAT is my problem. Very few non-scientists are able to understand the difference between correlation and causation (indeed a lot of scientists get it wrong!), and we run the risk of blaming the wrong cause.
5) OK... so do we amend the rule to "Don't go outside your training... unless you do so slowly and carefully"? Actually, I'm happy with that too. Phew Forrest... we're OK now with your going outside your training on the Home Depot special! Or we will be if you allow us to amend the Sacred 5 a little...
This was written about 15 years ago and has been around. Redundancy is good! It addresses the issues of this thread and I guess the question remains. "aainslie" is right about accident analysis correlation and causation being misunderstood and "quarrydivers" statement " because the only person who knows what actually happened is no longer there to provide the answers." So the question remains what do we tell the authorities, family, land owners and the cave divers where there is no line between correlation and causation.
Any public discussion of relaxing the rules from the most conservative recommendation does a disservice to cave diving. One thing I learned early came from an old navy instructor who said "I can swim for you, see for you, breathe for you but I can't think for you!" Link that with the basic rules and the sentence from the article "Only by allowing the unthinkable to enter into consideration can the serious cave diver expect to survive the unlikely." Plan your dives from this platform and go forward!
Read, think and plan safe dives then go enjoy the sport. /Ken
Exley's Razor
By R.D. Milhollin (c.a. 1995)
Sheck Exley was one of the most outstanding explorers of his time. Within the field of cave diving, he was virtually peerless. He was concerned from the early days of the practice with identifying factors involved in cave diver deaths. Exley was one of the first to use an analytical approach to assess the causes of cave diver failure. His actions helped define many of the commonly held limits in this field today. His business was limits. And he died diving in a cave.
Ockham's Razor: a principle formulated by William of Ockham, stating that terms, concepts, assumptions, etc. must not be multiplied beyond necessity. It is a limiting and simplifying guideline for inquiry and explanation,advocating parsimony over complexity. The admonishment to science has guided inquiry for over 600 years.
Exley's Razor: a proposal for discussion involving the nature of limits. One never truly knows one's limits until they are encountered. Once a limit is reached and exceeded, return is not always possible. This razor is dangerously sharp. It divides those seeking the knowable end from those who have found the ultimate destination.
The problem posed by this proposition holds great importance for the pursuit of cave diving. Some of the basic admonitions given to the student entering this pursuit deal with limits, specifically those of depth, horizontal penetration, gas supply, and reserve gas. The implications of breaking these limits are often assumed to be understood. They are probably better appreciated during the first few penetrations into an overhead environment than later, after a few dozen dives have been successfully completed. The idea of limits in cave diving can be approached in many ways and may assume the following forms: horizontal penetration, vertical depth achieved, hours submerged, distance traveled, speed of travel, gas supply and consumption, gas component depth/time considerations (i.e., PO2 depth), fatigue, physical and emotional stress, task complexity, and equipment considerations. Limits are imposed on students during training, and are impressed on novices by the cave diving community. There are limits imposed by landowners, by physics, and by the legal system. There are limits that are self-imposed, such as those related to practical, financial, or physical comfort. Some limits may be dictated by body size or health and fitness considerations. The limits to be addressed here are primarily those involving experience, mental and emotional states, family considerations, personal safety, and internal feelings of security. By analogy, limits may be envisioned as the ability for a particular material to recover its shape after being deformed by applied stress, a measure of tensile ability. Past some point the material will either break (fail) or will not be able to return to its original shape. Every cave dive involves stress in one or more of its forms, and the diver must strive to avoid reaching and exceeding the type of limit he might not be able to return from.
The least well known aspect of cave diving is the psychological. There are now and have been divers who will do things on a dare. For these people the ego may be fragile: once the ego is threatened, it can lead them into areas they know to be unsafe. The ego threat, if not controlled, can cause divers to exceed their own known limits of comfort. The fact that another diver completed a particular dive can be reason enough for the threatened ego of a weak individual to justify taking risks that might otherwise be avoided. A cave diver wishing to keep this potential threat under control might consider including "motivation" as part of the formal pre-dive planning process. This could help by providing an opportunity for the diver to assess the reason he or she wants to attempt a particular profile, and a chance to modify that profile if sufficient justification is lacking. By consciously considering the reason for choosing to attempt a particular dive, the diver is making the first step toward defining and enforcing the personal limits that will enable him or her to be comfortable while under taking this demanding pursuit.
It may be possible for properly trained (to standards) but ill-informed novices to get a false impression of how more experienced cave divers became that way. They see individuals going through training from beginning students to "full cave" certified in a surprisingly short amount of time, and assume this must be the best route to take. The instant gratification expected by the children of the instant culture of the 1950's onward comes into play. Mix a newly certified diver, lots of money (equipment), and the right amount of encouragement (from the instructor or through the social environment), and you have the potential for a cave diving statistic. Just add water! The fact that some lucky individuals actually survive while taking poorly calculated risks can boost confidence in underdeveloped skills and abilities, blinding them to the reality of their limited developed potential. There are novices who can see no difference between themselves and a diver who has been actively and patiently honing skills for 20 years or longer, building up a vast reservoir of reflexes and insights that will be there when needed.
The dividing line between the successful and the not-so-lucky will not be seen on the ideal dive, but instead, on the dive that had a problem. The experienced diver will know how to react when things begin going badly, and will be better prepared to recover presence of mind in time to make the crucial decisions that will save his life. This observation should be borne in mind by all cave divers, who must inevitably assess their own capabilities and set their own personal limits. These limits must be set based upon the worst possible circumstance imaginable, not upon what is likely to be expected. Only by allowing the unthinkable to enter into consideration can the serious cave diver expect to survive the unlikely.
There should be a division drawn between the recreational cave diver and the cave diving "explorer," for lack of a better term. It is recognized that exploration assumes a wide spectrum of activity, and the term is applied in this instance to denote the highly experienced diver who has been expanding his or her capabilities to significant levels over a considerable period of time and has made a conscious decision regarding the importance of cave diving in his or her life. The true explorer must carefully and continually assess the limits of his pursuit, allow them to change depending on any number of factors, and keep them always in mind.
To how many cave divers does this apply? How many are truly willing to take the chance and walk the razor's edge? Probably not a lot if it really gets down to serious thought about consequences. Perhaps that is what is needed: serious thought among cave divers. This process should probably begin at the earliest level of instruction, when the effects of inappropriate decisions or poor technique are explained. An appropriate observation is that when things begin to go bad in one area, there seem to be an escalating number of things that go wrong or appear to go wrong in other areas. If this process is not stemmed in time, the result will ultimately be diver failure. Of course in cave diving, this most always indicates death. There is little possibility of escaping with injury. It is no accident that the open water training sequence features rescue practice while cave diving has a course in body recovery.
The commercialization of cave and other forms of "technical diving" makes this discussion even more difficult than would otherwise be the case. The proliferation of "professional" instructors carries with it the implicit fact that they must earn a living and are hence prone to advertise their services to the general public, and may be less apt to deny a student with marginal skills or a poor attitude access to a course. The rent needs to be paid. Encouraging students to participate in cave diving courses not only defeats any serious attempt at screening for personality types not suited to the pursuit, but invites much greater damage to the cave environment than is absolutely necessary for training and learning. There is a cost associated with the commercialization of cave diving that may not be readily apparent except to those willing to look past personal objectives to see the greater whole. The traditional cave courses were not openly advertised and students were not sold this form of diving as a product. Both of the major training organizations have discouraged the "promotion of cave diving," but have shied away from defining what "promotion" is specifically. New cave divers were once expected to systematically work their way from simple dives to more complex dives, slowly, over time. The idea of "progressive penetration" was espoused by those who had learned that way, and had accumulated impressive numbers of successful dives following this dictum. Of course, in the early days of cave diving, the idea of a serious dive was something much different than what is commonly imagined today. Some of the early pioneers racked up thousands of cave dives over relatively short periods of time, for these were quite short penetrations by today's standards. There have always been those who tested the limits, as can be attested to by the exploits of Wally Jenkins and his Wakulla Springs team, among many others. Given the same circumstances, it is unlikely that many of today's experienced cave divers would be able to (or want to) accomplish the same feats that were undertaken in the 1950's and 1960's.
Given the nature of cave diving limits, recreational cave divers should stay well away from where they feel their own limits might be to avoid the possibility of exceeding them. But how is one to know where those limits lie?
As mentioned previously, students and novices have the benefit of ready-made limits handed down by more advanced and capable practitioners who have successfully gone through the learning process themselves. It should also be pointed out that the basic rules of accident analysis were derived from the observations of circumstances surrounding those who were not as successful. As the novice progresses, and experiences gained through time spent in the pursuit begin to add to his or her confidence and abilities, the task of redefining limits is encountered. How this is done is largely a personal matter, but it is likely that an honest appraisal of one's physical abilities and overall preparedness would allow most to define reasonable limits. Adherence to these standards, once drawn, is again a matter of personal integrity, and when to enlarge the scope of what one allows oneself to do is strictly subjective, for limits must be expanded as the diver grows. The immediate importance of achieving a goal can lead to extending beyond where one feels comfortable or safe; this is what needs to be avoided. Do limits need to be reviewed? Should the community address the subject of specifically recommended limits for novices versus "explorers"? One suggestion might be to have novices complete personal inventories during cave diving training detailing all they may have to lose if they were to die as a result of exceeding their limits. Spouse, children, other family, career, material possessions, the opportunity to make other dives, etc. would invariably crop up during this process and could help the introspective student realize the importance of adhering to known safe standards. Students and novices gaining experience should ask themselves honestly how they rate in terms of cave diving wisdom, and set their personal limits accordingly. The community might consider an attempt to further define limits for recreational versus exploration dives in terms of decompression times, number of cylinders, or any other arbitrary recommendations, but the ultimate responsibility for personal safety and comfort lies with the diver.
Explorers have to set limits just as novices do, but they have more knowledge, time and experience under their belts, are generally capable of more efficient swimming, and have mastered more advanced techniques. These are personal decisions with profound consequences. The nature of this type of decision is what should be provided to the student and novice through course content, the example of other divers, and possibly through signs similar to the type used to warn untrained individuals of the general dangers of cave diving" The recommendations of any outside group, whether governmental, training agency, diving community, or more experienced friends, will ultimately be just that: recommendations. We must realize that the best of recommendations are easily disregarded by the irresponsible, and that unfortunately the training of recovery divers will still be needed in the foreseeable future.
Sheck Exley exemplified the ideal cave diver to many people. His experiences are well documented through his years of service to the NSS-CDS and to Underwater Speleology. His discoveries and successful ventures earned him the admiration of a diverse set of communities, from adventure seekers to scientific investigators. It is not ironic that his death can be looked upon as a source of information to be used to inform other cave divers, for this process is exactly the contribution that he made to the understanding of cave diving deaths. Exley's findings are not written in stone. They are subject to update. There is a blank space remaining under the fifth rule of accident analysis.
That's a great article, Ken! Thanks for posting it, it's funny how a 15 year old article applies today more than ever.....
Safe diving,
Rich
I am so tired of saying this but let's try one more time. Maybe caps will help.
1) MODIFYING THE RULES DOES NOT NECESSARILY MEAN RELAXING THEM.
They are seriously outdated. Siphons... scooters... many situations are poorly handled.
2) THE AIM OF ACCIDENT ANALYSIS IS NOT TO FEEL WARM AND FUZZY, BUT TO SAVE LIVES. Frankly when it comes to accident analysis, I don't give a crap about the bereaved. There are better ways to handle their grief than to use poor science and dogma to provide a "reason" for their deaths.
Good grief.
Finally, I REALLY don't like that article. It starts with Occam and Exley's approach to an intellectual endeavour, then is against the use of intellect to further the sport for the rest of the article.
As the authr says, knowledge, time and experience are useful. Thought is even more useful. Any animal, given sufficient repetition, can learn a pattern of behavior. The human is unique in being able to step beyond this, using inference, logic and the rest of our arsenal of superior mental skills to move beyond learning through pattern recognition. In aprticular, mere pattern recognition is highly dangerous since it doesn't allow for prediction, i.e. at its simplest level, "what if" analysis. You just bumble along and if you accidentally survive a threatening situation, THEN you learn from it. Dangerous stuff.
In particular, peer reviewed thought (which seems to work in EVERY field.... except, according to a bunch of you, cave diving) can lead to better practices.
So... are we going to think a little about our "rules"? Or lazily decide that all the work was finished in the 80's and we now have a perfect set of rules?
Utter crap. And it will continue to kill.
Quote:
Originally Posted by Ken Hill
I wonder if Sheck was thinking of this as he tied himself off to his decent line at 800 plus feet on open circuit scuba?
I don't know. You haven't met my dog. Sweet, loyal, but never going to make it to the boardroom, if you know what I mean :-)Quote:
Originally Posted by aainslie
Quote:
Originally Posted by aainslie
aainslie ... the clock is now ca 2000 and your statement is not unlike GI III who addressed the same points and referred to the status quo and cave divers in general as "farm animal stupid." After many incredible dives at WKPP, setting endurance, penetration and equipment standards a lot of good ideas came forward. New training instruction, ideas and configurations resulted but the basic rules of accident analysis remained.
The internet seems to have supplied numerous thinkers from the very capable to some self taught egoists and let’s not leave out the narcissists who seem to come and go. Yet the old boys that dive their backyards seem to do some really incredible dives and have done so for generations with less incident than those that try to find that razor's edge a couple of times a year. We learned this from WKPP who did build up dive as a prelude to some of their exploration.
This is all good stuff for a workshop where a room full of trained cave divers will benefit from serious discussion. But back to beating the dead horse ... preaching conservatism on a public forum is the right thing to do. Anything less sends a wrong message. /Ken