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OK Jim, Yes this again. Since you seem to know everything, I'd like you to tell me=20 that if getting out of the water in the least amount of time (safely,=20 according to decoplanner) isn't the primary objective, then just what in the= =20 hell is. Decoplanner showing your needing less deco means that everything is in the=20 right direction. The nitrogen is gone quicker from your body and with no=20 oxygen toxicity worries, so what else is there that's "the primary objective= .." Also, since the EAN36 and 80/20 actually gives you less deco then your EAN50= =20 and 100% oxygen, you can throw just about every single one of your Baker's=20 dozen commandments in the trash can. They just don't hold up. Unless of=20 course, you mean to say that decoplanner is giving the wrong answer. So take your patronizing attitude and go stuff it where the sun don't shine.= =20 When you have something intelligent to say then maybe I'll listen. Untill=20 then, which will be a very long time I'm sure, just try to go play bully wit= h=20 those that mistakenly believe that you actually know something about diving. Karl In a message dated 8/26/00 6:35:03 AM, cobber@ci*.co* writes: << Oh, no, not this again... >> The fact is that getting out of the water in the least amount of time should not be the primary objective. Do us all a favor go to Kevin Connell's archives and do a search for 80/20 or Bakers Dozen and save us a lot of bandwidth. http://www.nwls.com/list-archive/ If you have any additional questions, come on back and ask. Jim ------------------------------------------------------------------- Learn About Trimix at http://www.cisatlantic.com/trimix/ > From: <KRussellTX@ao*.co*> > Date: Sat, 26 Aug 2000 02:30:37 EDT > To: techdiver@aquanaut.com > Subject: 80/20 deco >=20 > I have been reading in this group how 80/20 is not the gas to use for deco= .. > I have also been reading that Decoplanner is great and EAN50 @ 70 ft. and=20 100 > % oxygen at 20 ft. is the DIR way to go. In truth I haven't got the > slightest idea what the "oxygen window" means unless it simply refers to > using the closest PO2 that is below 1.6 that you can get to. >=20 > Now the question I have to ask is that if 80/20 is only used by strokes, w= hy > is it that on a dive to 200 ft. on 18/35 for 30 minutes, doing a deco usin= g > EAN 36 @ 110 ft. and EAN 80 @ 30 ft. actually results in a shorter deco th= an > EAN50 @ 70 ft. and 100% oxygen @ 20 ft.? >=20 > Any explanations why the stroke mix seems to get you out of the water=20 sooner? >=20 > K. Russell In a message dated 8/26/00 1:16:10 PM, Michael.Waldbrenner@wa*.de*=20 writes: << >terms of the O2 clock. I was not able to find the bakers dozen for oxyge= n. Here you go ! 1997 ! Just for the record here on Quest. Tom Mount is writing in the rebreather forum that IANTD is using EAN80 for OW-Deco. When doing some of my courses at Billy Deans in Key West a few years ago, we were mostly using surface supplied oxygen for the deco-dives. And to the ever-occuring buoyancy thing.... Deans was very strict on these things like buoyancy, beeing on time, beeing fit, etc... I remember he=20 kicked one guy out, because he did not arrive on time at the dock to leave=20 for the dive in the morning. Billy told him: "You are not in time at the boat, so you will not be on time at the stops". Deans was IANTD #2 and he was using O2 ! I don=B4t want to speak for IANTD,= =20 but i think Billy Deans was right ! Michael > ---------------------------------------------------------------------- > A (BAKER'S) DOZEN REASONS WHY WE DO NOT USE 80/20 (By George) >=20 > 1) This gas was introduced in an effort to overcome the inability of > unqualified student "tech" divers to control their buoyancy in open > water, and is as such is yet one more concession to doing things in a > convoluted fashion to offset a self- inflicted set of problems brought > on by the "doing it wrong" thinking that pervades diving today. >=20 > 2) A heavy sea is not a problem for a deco stop if it is not posing a > lung-loading problem. Look at your depth guage in a heavy sea and "see" > for yourself what the changes are - insignificant, and if they are not, > you should either not have been diving or incurring a decompression > liability of this magnitude in the first place. In the event of a change > in conditions during the dive, see below where the 80/20 becomes a > liability rather than an assett. >=20 > 3) In the interest of using a standardized set of gases for which you > can permanently mark your bottles , it is a poor concession to inability > to sacrifice the benfits of pure O2 to accomodate a real or percived > lack of skill - learn to dive before taking up techdiving. >=20 > 4) In this same interest you will find that when you graduate to real > diving, as in caves, you will not want to accellerate your ppo2 at > lower depths while still being faced with a long decompression at > shallower depths, and making bizarre mixes to do this is a dangerous > mistake (just like the fantasy of holding an accellerated ppo2 on a > rebreather throughout a deco). I am anticipating the thinking that the > 80/20 crowd would then go to an additional oxygen in cave without > accounting for total exposure, and subject themselves to the risk of tox > in the final deco steps. Tox you do not get out of - bends you do. >=20 > 5) The 80/20 mix is in fact totally useless and contraindicated as a > deco gas. At thirty feet it is only a 1.52 ppo2 ( the real 1.6 ppo2 > gas would be 84/16) and as such does not either provide the right > oxygen window, nor does it does it work as well as pure oxygen without > an inert gas at any depth. The gas mixing in your lungs has already > lowerd the effective ppo2 enough to prevent spiking at 20 feet anyway > with the use of pure oxygen - in other words, we aer dealing with a > simplisitc misunderstanding here, or "old wives tale" that is typical in > diving. >=20 > 6) If 100% oxygen is a percieved buoyancy control risk at 20 feet, then > why is the same ppo2 ( intended) not a risk at 30 feet? This shows the > total lack of reasonable logic involved in the decision to use this gas, > as well as a lack of understanding of the whole picture ( see the rest > of this discussion). >=20 > 7) Along those lines, all we hear is howling about "oxygen cleaning" > above 40% mixtures, and dive shop proprietors on here complaining about > scuba tanks with oxygen in them being filled in their shops. With a > pure oxygen system, the tank only ever gets filled with oxygen from > oxygen tanks, not from every dive shop compressor it sees. Again , this > shows the total inconsistency of agency thinking, and reveals that the > true reason for this gas is to pretend to lower liability for teaching > incompetents to dive, which is bull, and to attempt to accrue some > inventive accomplishemts to the dive agency pundits who themseleves > prove that they do no real diving by making this recommendation > in the first place. This is like the colored regs, the stages on either > side, the quick-release buckle, and the poodle jacket: nonsense of the > most obvious nature developped through one-dimesional thinking by those > whose universe of understanding is not only severly limited, but blinded > by the hubris of not being the "inventor" of the techniques that work. >=20 > 8) Any perceived decompression benefit of using a higher ppo2 at 30 > feet with 80/20 is then given back by the lowered ppo2 at 20 feet, not > to mention the fact that the presence of the inert gas in the breathing > mixture defeats the purpose of using oxygen in the first place ( see > the Physiology and Medicine of Diving) . The ppo2 of 80/20 at 20 feet > is 1.28, not much of an oxygen window, and at 10 feet it is 1.04 - > useless for deco. To make matters worse, you can not get out from your > 30 foot stop in an emergency ( not doing the other stops) on the 80/20 > mix without really risking a type 2 hit. >=20 > 9) This is a dangerous method to achieve a greater total volume of gas > for the bad breathers (another obvious reason the gas is in vogue), who > should not be incurring these decos, and even that benefit of having > more gas is lost since it is breathed at 30 feet, and then has to last > for the other stops. The fact is that gas is effecively saved by using > the lower deco gas up to this point, relying on the pressure gradient > to both achieve the deco and provide a break from high the previous > gas's higher PPO2 prior to going to pure oxygen where the spike could > be a problem on an extreme exposure without an adequate low ppo2 break ( > again this shows that the 80% user is a neopyte diver with no real > experience or understanding of the true risks of these dives) . >=20 > 10) The 20-30% longer 30 foot time on the lower ppo2 is not only > overcome on the pure oxygen at the next stops, the breaks do not come > into play until the initial good dose of pure oxygen has been absorbed, > since you are not spiking from a high pervious dose without a break > that is effectively achieved on the previous gas. These things need to > be understood and taught by the agencies, not some superficial > convolution that is designed to obfuscate the problem rather than > openly acknowledge and deal with it in a responsible fashion. >=20 > 11) In an emergency situation, getting onto the pure O2 for 20 minutes > or so (for long dives something approximating the bottom time or a any > decent interval) would give you a real good shot at getting out of > the water having missed the rest of your deco and living through it > with pain hits only. You have to think these things all the way though, > not go for the transparent superficial thinking of those who merely are > trying to "make their mark" with some "great" idea they can call their > own. The acid test is , as always, is the caliber of the divers who > adopt these practices. >=20 > 12) If there is some problem with your deco or you otherwise develop > symptoms and need oxygen either on the surface or back in the water, it > is silly to have not had it there all along. 80/20 is a joke for that > purpose, unless you have asthma, in which case any accellerated oxygen > mix would be a nightmare. This is again part of the "thinking it all the > way through" phiosophy which is obviously mising from the 80/20 > argument. >=20 > 13) Only a card-carrying stroke would do somethng like this, and > showing up with 80/20 is no different than wearing a sign on your back > saying "I am a stroke, and have the papers to prove it". It announces to > all the world that you have no clue, kind of like wearing clip-on > suspenders or having dog dirt on your shoes. >=20 > George Irvine > Director, WKPP > "Do It Right" (or don't do it at all) > ---------------------------------------------------------------------------- - > Bill Mee's post: >=20 > George, >=20 > Thank you for exhaustively laying the reasons why we or anyone else > should not use 80/20. The only thing missing from this discussion is > the Q.E.D. at the end. >=20 > Reason #8, reiterated here for discussion purposes is perhaps the > soundest reason, among many very cogent ones, as to why this practice > should be avoided: >=20 > " Any perceived decompression benefit of using a higher ppo2 at 30 feet > with 80/20 is then given back by the lowered ppo2 at 20 feet, not to > mention the fact that the presence of the inert gas in the breathing > mixture defeats the purpose of using oxygen in the first place ( see > "The Physiology and Medicine of Diving") . The ppo2 of 80/20 at 20 > feet is 1.28, not much of an oxygen window, and at 10 feet it is 1.04 > useless for deco. To make matters worse, you can not get out from your > 30 foot stop in an emergency ( not doing the other stops) on the 80/20 > mix without really risking a type 2 hit. " >=20 > The rush to embrace this practice, recommended by technical diving > diving opinion leaders, was widespread and in retrospect, irrational and > poorly thought out, like so many of the "trial balloons" in this field > of endeavor. It seemed to many, at first glance, to be a simple means of > increasing one's supply of deco gas while eliminating its bothersome > volume and mass. In fact, the perceived benefits tranform into > liabilities when subjected to a thoughtful analysis. When you view > decompression as a two pronged challenge: to progrssively widen the > oxygen window and increase the diffusion gradient to maximize passive > transport of dissolved inert gas, it becomes clear that the 80/20 > solution falls short on both requirements at a critical point in the > decompression profile. >=20 > Section 11 emphasizes a very compelling argument for those who are > concerned with managing dive related crises. When diving in the open > ocean divers and boat operators should always be prepared to "scram" the > deco at any time. This could be for any number of reasons, not the > least of which might be a sudden change in the sea conditions or > unscheduled events such as dive accidents or impending ship collisions. > Just follow the Whitefish Point thread for an excellent example of why a > deco may require being aborted (or never started in the first place). >=20 > Most unfortunately the "80/20 problem" bears a strikingly resemblance to > several other ad hoc technical contrivances mentioned in this same > article (section 7) i.e. dual bcs, colored regulators, bilateral stage > bottle postioning, poodle jacketed second stages and harness quick > releases. All of these ideas, while seemingly reasonable, become > tainted when subjected to thoughtful review. >=20 > Good show Director Irvine. >=20 > Bill Mee -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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