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O.K., it's time for me to jump in on this one. My apologies to everyone who doesn't like me. I feel a strong need to address a couple points that have been touched on in this thread. First, Cis-Lunar. Because I've been using their prototypes units, I think a lot of people look to me as some sort of spokesperson for them. I am not -- I have no business affiliations with Cis-Lunar. I've seen a number of personal and private communications containing crticisms of Cis-Lunar's "secrecy" about what they're up to. I am in no position to criticize OR defend them for this secrecy because I am a biologist, not a businessman, so I simply do not understand the dynamics involved. Personally, I really don't care what the dynamics are. What I DO understand is that, as part of the agreement I have with Cis-Lunar, I am not allowed to disclose certain aspects of the rig design to anyone. If I violate this agreement, they will take the units away from me. That would be a VERY, VERY BAD THING!! As much as I like to share information on this list, and as much as it PAINS me to see so much INCORRECT information about Cis-Lunar's and others' rebreathers posted on this list, it's just not worth it to me to risk having the rebreathers taken away. Sorry folks, I hope you understand. If you don't understand...well...tough luck. Yes, I do know a lot of stuff about Cis-Lunar, the design of their rebreather, and their plans for the next generation. I can say these things: 1) Yes, there will be a Cis-Lunar "Mk5", which will not resemble the Mk4 prototype on the outside, but will have all the basic elements and increased capabilities on the inside. 2) I will eagerly part with a year's pay to buy one (they have not offered, nor have I asked for, any discounts) as soon as they become available. One more thing. I have a strong suspicion that one of the reasons Cis-Lunar has been so quiet about their progress is that they don't want to play the sales game by touting "vaporware" before they are ready to deliver a quality product. They knew the Mk-4 Prototype was not something they would ever want to sell to J.Q. Public, so they are waiting until they can deliver a REAL product before they go blowing their own horn. They started off with the "It'll be here by the end of the year" approach, and I think they decided this was not the best way to procede. Bear in mind, this is only speculation on my part, I do not know anything about their business strategies. Second, 4-hour rebreather IT's. I actually don't have a problem with this, largely because, as Dennis already pointed out, few or none of these people are actually trying to teach rebreather diving to anyone. I have no doubt that most or all of these individuals are fully capable of teaching the *theory* of rebreathers to students. The only time I will be concerned is if any of these individuals get it in their heads that they are ready to start teaching the *practice* of rebreathers. Todd Ives said it well -- with more than 100 hours on his rebreather, he still considers himself on the learning curve. I am in essentially exactly the same position. The more hours I accumulate, the more I realize how inexperienced I really am. These things require a LOT of time to fully appreciate and understand. The difference between an experienced trimix diver and a qualified basic rebreather diver is GREATER than the difference between a non-diver and an experienced trimix diver. Third, although I'm really very new to the whole rebreather scene, I do have some opinions about what are the big risks and concerns, and what are not the big risks and concerns. I see a lot of talk about what rebreather brand or model is better, what desgins are better, semi-closed and fully-closed, etc. While these things may be important at some level, they are DWARFED by a much greater problem that I have so far only seen mentioned by Jason Rogers (in private) and Bill Gavin (in public). That is, it doesn't matter very much what kind of rebreather you have, or what sorts of redundancy it incorporates, or what kinds of bailout options you've set up, once you are unconscious. Always remember, the whole point of all diving technology is to provide you with a life-sustaining breathing gas. I don't care what kind of rebreather you have, or how many O2 sensors and computers it uses, you will never have as much confidence that the gas you are inhaling is life-sustaining on a rebreather (fully-closed *OR* semi-closed) as you will on open-circuit scuba. In my opinion (which is subject to change as I accumulate more experience) every rebreather diver should enter the water with the assumption that none of the electronics will work. In other words, the diver must be confident that he or she can maintain a life-sustaining breathing mixture in the loop at all times without the aid of electronics. This is generally easier to do on a semi-closed system than it is on a fully closed system, because most semi-closed systems are designed to operate without the need for electronics in the first place. However, semi-closed systems do not provide anywhere near the same advantages of a fully-closed system, so the trade-off becomes one of capabilities vs. complexity of operation. Getting back to the REAL problem of fully-closed (and perhaps even semi-closed) rebreathers -- unexpected unconsciousness -- the difference between life and death here is NOT the design of the rebreather, it is the attitude and discipline of the diver. Sure, a well-designed rebreather will give all kinds of warnings to you and/or your buddy when the computer(s) register a dangerously low or high PO2, but these can be a double-edged sword. While warnings and redundancy of electronics can increase the chances of keeping a well-trained diver alive, they can also increase the chances of DEATH in a diver with the wrong attitude. In this case, the wrong attitude is *COMPLACENCY*. As we have heard in other recent threads, complacency KILLS! Faulty equipment doesn't kill divers anywhere near as often as diver's mistakes kill divers. Most of my closest calls involved situations where I neglected to respect the true extent of risk I was undertaking. Consistently staying alive on a rebreather means you must always assume the electronics are not giving you correct readings. A well-designed rebreather will provide the user with the tools to verify whether or not the electronics and sensors are working correctly, but those tools are useless if the diver neglects to take advantage of them. Rebreather diving will ALWAYS require more attention than open-circuit diving. The questions each of us must ask ourselves are: 1) Are the costs of increased attention worth the benefits provided by rebreathers for me? and, 2) Do I (honestly) have the discipline to maintain that level of attention on EVERY dive? Think long and hard, because your life is at stake. O.K., off my soapbox... Aloha, Rich
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