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>snip- >Dan, been very busy, so couldn't respond any sooner. > >First, let's look at "no bubbles". Semi-closed rebreathers *ALWAYS* vent >some amount of gas (except sometimes on descent). There is no such thing >as "no bubbles" with a semi-closed system. There are a number of semi- >closed rebreather folk who make such a claim, but IT SIMPLY AIN'T TRUE! >In fact, systems that work on a similar method as the Odyssey tend to >vent MORE gas than some other semi-closed systems because it is always >venting a constant percentage of each breath, albeit depth compensated. WRONG!!! I don't think you understand the differences between the Odyssey and the other rebreathers yet....the Odyssey near surface exhausts 20% on each breath, but at 99 feet you exhaust 5% , and as the depth increases, the percentage gets smaller. The mass stays constant, but the volume exhausted decreases with depth. This is why the Odyssey is almost as efficient as the Closed Circuit rigs on a 300 foot dive, but without their electronic nightmares. >A closed circuit rebreather, on the other hand, is "bubble-free" except >on ascent, when the expanding gas has gotta go somewhere. Because the volume exhausted at the surface, at 100 feet, or 200 or 300 feet is so small, the amount of air escaping can not make much noise---and the Odyssey channels the exhausted air through a mechanical system that causes the bubbles to break up and to leave as bubbles too small to be significant. Since I was talking about what you can get out of "A Rebreather" here, there is no problem with what I said. Closed circuit rigs, and even the Odyssey with its small diffused bubble stream, will satisfy fish watchers . > >Secondly, "Huge bottom times" is an accident waiting to happen, or at >best, a disappointed customer. Mike, I assume you are talking about the Prism II here..;-) This would relate to poor diver training, or reliance on a rebreather without a functional bailout system and stages within reach in the time allowed. You must not be talking about the tech market. > >snip-,... saying that one can take a rebreather to "extreme depths" >without qualifying the statement is, IMO irresponsible or misinformed. Mike, WHAT are you talking about ? The concept of a rebreather for the 90's is NOT synonymous with shallow diving---sure, a few of the rebreather companies have gone that route, but that does not change rebreathers. You again are showing that you have not done your homework on "Understanding Rebreathers 101" :-) >One of the common scary statements regarding Nitrox is "Let's get Nitrox >certified so we can go really deep." Mike , I did not start any mis-information, and in fact I mentioned Odyssey as a semi-closed system----the Odyssey runs any mix you want to put in it. And it does it Better than any of the closed circuit , active addition systems, because not only does the Odyssey user know his PO2's at any time, but he will also no his FO2. Just because one or two rebreathers are bad, doesn't mean ALL rebreathers are bad ;-) Most semi-closed systems use >Nitrox, which, when everything works, and you appropriately limit your >depth, is great. However, they are certainly not capable of "extreme >depths" per se. The only exception to this that I know of is non- >nitrogen based rebreathers. Is the Odyssey helium compatible? The Odyssey was designed to use nitrox, trimix, heliox, whatever. As an >aside, in rebreathers, the amount of O2 being breathed is less than what >is in the cylinder because some O2 is metabolically consumed. In >mechanical-only rebreathers a higher than required amount of O2 must be >in the breathing loop because the system does not "know" how much O2 >that particular diver in his current situation is metabolizing. WRONG!!!! Mike, since you continue to mention the Odyssey , how can you set yourself up like this??? This is only true of active addition semi-closed systems. With passive addition systems like the Odyssey , its keyed to RMV therefore metabolic requirements are a non-issue. Diving it is like NOW LOOK WHO IS SPREADING "MISINFORMATION"!!! . > >>The real issue here would be the probability of an electronic failure, >>and if planned redundancy will work if electronically based. Some day >>this will be the answer---we don't know if it is today or not. > >Dan, we think it is in the PRISM II which works in any of these modes: snip- >The PRISM II comes with an independent PPO2 monitoring system that, in >the event of a main computer and/or mechanical controller crash, allows >the system to be flown manually. Mike, your getting far beyond your own understanding of rebreather technolgy here, and beyond where I feel comfortable arguing----I am going to quote Jack Kellon to you and the list for a far more definitive understanding of rebreather safety and functioning. Dan Volker SOUTH FLORIDA DIVE JOURNAL "The Internet magazine for Underwater Photography and mpeg Video" http://www.florida.net/scuba/dive 407-683-3592
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