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Chris, > So, do you use full redundancy when diving now? (Just curious what > equipment and practices you use at present.) Whenever it's called for. Generally, if I'm going below about 120', I want a full back-up regulator (i.e. Y-valve, 30 cu ft. pony, or doubles with twin reg manifold) - not just an octopus, but two independant regulators. The mixed-gas diving involves a great deal of system redundancy, which would take me too long to explain here (my rig was described in detail in AquaCorps:MIX, and diagrams of it appear in "Deep Diving" and "Mixed Gas Diving" (Watersports books). Basically, the most likely ways I can die underwater are from a direct or indirect result of: 1) equipment failure 2) gas mis-management 3) entrapment or entanglement at depth 4) "unearned" DCS 5) Shark attack I deal with equipment failure by providing adequate redundancy. I deal with gas mismanagement through personal training, drilling, and discipline. I deal with entrapment/entaglement by never diving in "real" overhead environments (caves, wrecks, etc) at depth; and I designed my rig to make it VERY easy to climb out of....I also avoid lines & such which might snag on my rig I deal with "unearned" DCS by following VERY conservative profiles, and by having all the necessary equipment ready to allow for immediate in-water recompression. As for sharks, there's not very much I can do about them....I do what I can, but they are largely beyond my control. In general, if I've reduced the likelihood of a problem occuring because of numbers 1-4 below the probability of a shark attack (i.e. if the MOST likely cause of my underwater death is a shark attack), then I have succeeded in my efforts. Basically, the probability of my dying at the maw of a shark is so teeny tiny, that it's not a large concern. In fact, I'm probably MUCH more likely to die in a car accident on the way to the dive site. Ultimately, I want the drive to the dive site to nbe the MOST dangerous part of the dive. I'm not at that level yet, but I'm working on it. This deals with dying underwater. As for the long-term detrimental effects to my body....well...who knows. It seems like almost every activity, every food, every EVERYTHING has SOME long-term detrimental effect on our bodies. The question is, will this detriment significantly impair our lives before we die at a ripe-old age of natural causes (assuming we make it that far). I honestly don't know. I know I am sustaing permanent damage from deep diving, but as I've said in earlier messages, I'm not sure how much. This is why I am continually trying to expand my knowledge on diving physics/physiology (and biochemistry! ;-)/rat), so I can learn how best to minimize these long-term effects. > Also, how does one manage > that with a rebreather? I would think the complexity of a rebreather > would mean a greater failure rate. Is that true? Also, do you breathe > mixes now when going below 200', or does the high PPO not bother you? Yes, rebreathers are much more complex, and therefore have many more components which might fail. But that doesn't necessarily make them less safe. There are two general sorts of failures (it's really a continuum, but it's useful to define each end of the continuum): Component failures, and System failures. The former involve malfunctions in certain components, and the latter involve life-threatening situations. You can increase the number of component failurs that can happen without causing a system failure by incorporating redundancy. One way to provide redundancy in a rebreather is to have two complete systems: 2 counterlungs, 2 scrubbers, etc. This, however, is likely to be excessively bulky & expensive (and virtually useless for my work....chasing little fishies). Another way is to make the back-up an open-circult system. In otherwords, use a large-capacity diluent bottle and have some oxygen in the diluent. With appropriate Y-valves and backup 2nd satges, and stage bottles & surface support, you can plan for a complete open-circuit bailout of a rebreather dive (taking into account all necessary changes in decompression profiles, etc.). Yes, rebreathers have many more components than standrd SCUBA, so they may be prone to higher rates of Component Failure; but if they are designed correctly, then it will take many MORE of these Component Failures to cause a System Failure. Bottom line: if you can make shark attack the most likely cause of a problem underwater, then you've succeeded. I hope you don't mind the long response. I decided to CC it to the techdive forum to see if there is any reaction or further input. Aloha, Rich
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