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Wrolf, Kinda strange, isn't it, diving a computerized rebreather without adequate bailout? I might also add that I believe that 6 people have perished diving the Inspiration since it's inception, three of the 6 were revived leaving a deficit of three or so. Actually a real nice guy, Martin Parker, builds the Inpspiration. His dive equipment company manufactures top quality gear in the UK, but despite this he still labors under the delusion that a fully closed circuit computerized rebreather can be made to work. Parker is very honest and very forthright about the problems which have beleaguered the Inspiration, but these only reaffirm his belief in the unreal alchemy of electronic rebreatherism Besides drowning, which is always the ultimate cause of death, there are two primary modes of killing that a fully closed rebreather (CCR) utilizes. The first one, common to all types of rebreaethers, is hypoxia, but the second one, unique to closed circuit and especially electronically controlled devices is hyperoxia. In the case of the Inpsiration, which utilizes features found on some of the "best" electronic rebreathers, the addition of oxygen is under microprocessor control. Like most of these devices it uses three oxygen sensors placed strategically within the breathing loop to sample the ppo2 of the breathing gas. In a perfect world the computer interrogates the sensors and adds oxygen when the level in the breathing loop falls below the setpoint. Obviously, if the sensor gets the wrong reading the computer will not make the correct decision and either add too much oxygen or not enough. This of course, assumes that there are no "bugs" in the firmware of the controller, something which plagued early versions of the Inspirations. The techno geeks, who swear allegiance to electronically controlled rebreathers will assure you that these things are bullet proof and electronics are used to control all sorts of life support systems. Still, electronics are only as good as their sensors and when the sensors do funky things the results can be unpredictable. The experts who pontificate about the virtues of electronic rebreathers will reassure you that their rebreathers are immunized against sensor failure. They get around these problems by writing software (and other very fuzzy logic) to discount sensors which provide out of range readings and they place hydrophobic membranes over the sensors to socalled "water proof" them. Go figure the firmware for yourself, but the one thing the geeks don't tell you is that the hydrophobic membrane, which does a good job at keeping the old h2o liquid out, admits water vapor can condense on an internal membrane within the sensor. This condition is not a happy one and can lead to the sensor giving an artificially low reading, which in turn causes the processor to do what? The funny thing is that you can flood one of these things and they will appear to give correct readings for a while. Even if everything works right there is such a thing in socalled "tech" diving known as task loading. Everybody on this list who dives understands task loading without my explanation. While you are preoccupied with bagging some loot from a shipwreck your display starts flashing you or some such warning and you are too busy to notice it until it is too late. That is the part the manufacturers like to call "diver error". The real error is diving one of these things in the first place. The problem in the UK is that mixed gas is very expensive, the Inspiration is very inexpensive by any standard and you have lots of fearless people with brass balls and 5 centuries worth of shipwrecks. A volatile mix. For most of what everyone on this list does stateside there is no real reason to use a rebreather. Virtually everything can be done open circuit. We use a semi-closed circuit rebreather for certain of the extremely long range dives performed by the WKPP. This is a necessity for logistical purposes only. On our rebreather, which is not electronically controlled, the singular mode of death is hypoxia and you are very careful to monitor yourself and your team mates for the presence of gas addition. Looking closely at the subject of CCRs and their fellow travelers is like lifting up a paving stone and observing the isopods, centipedes, and other invertebrate life scurrying away. A strange, contradictory and scary mix. You have touched on a very interesting topic which needs more light shed on it, especially since the flock which worships at the altar of electronic rebreathers is growing dramatically and there are several US projects where volunteers will soon be subjected to the uncertainties of these devices. Either that, or sooner or later soneone will show up on the Wahoo with an Inspiration or one of it's cousins. Regards, Bill Mee Wrolf Courtney wrote: > > > Frank Sonnemans wrote: > > > > The following comes from the July issue of the UK dive magazine Dive > > International: > .... > > ---------------------------------------------------------------------- > > > > The same magazine reviewed the Inspiration rebreather, a close circuit > > system with active, computer controlled Oxygen addition. Three out of > > seven units failed with water in the electronics at the start of a > > training session in Egypt. The units were used for 4, 150 and 300 > > hours respectively and only had the flight to Egypt in common. > > > > The article reported that 120 inspiration rebreathers have been sold > > and that 250 people completed training. > > > > The rebreather contains two 3 liter cylinders, diluent and oxygen. The > > system is controlled by 2 computers and was tested by the Royal Navy > > and has CE approval. > > ---------------------------------------------------------------------- > > It would be interesting to know if Paul Haydon died because of an > > equipment failure or user error. Unfortunately I have no contacts in > > the UK who could find out. > > > > One of my concerns with this rebreather (other than problems with the > > oxygen percentages) is the size of the cylinders, which do not contain > > enough air for a safe open circuit bailout from a deep decompression > > dive. > > Thanks for the information. This was very helpful - the number of units > was an open question for me, and the lack of an effective open circuit > bailout option was a complete surprise. > > The Royal Navy testing, and the portrayal of it by the manufacturer, > apparently has the Commander in charge of that unit hopping mad. > > I do not have a date for the Coroner's report, but I expect to get it > soon after it is released. > > It is clear to me that this unit may be a widow maker. > > -- > Wrolf > > Wrolf's Wreck: http://www.concentric.net/~Wrolf > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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