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on 8/2/00 10:37 AM, billy@bd*.co*.au* at billy@bd*.co*.au* wrote: > Seems Maffatone is determined to take an outdated > and terminally stupid idea and grind it around and > around some-more. > > The old Kevorkian rig rears its ugly head again. > > rgds billyw Billy, Everyone on this list who dives using any non-air mixes should read and reread this accident report. It goes directly to the question of gear configuration and how deadly it can be when poorly designed. Maffatone's system is not new or even all that creative, he's just getting press while he's still alive. There's a reason you are supposed to recheck your cylinders when getting Nitrox fills. Some fill-stations utilize a gas-block system to run all fills through a few whips. You check your fill to prevent accidents later when underwater from a hot mix. If it's common sense to do an O2 check after a Nitrox fill on the surface and then mark each cylinder, how are you supposed to be sure you have the correct gas at depth with a gas-block device? There have been several suggested systems to prevent breathing the wrong gas and many rely on a physical separation of the O2 or Nitrox regs from bottom mix regs, coupled with various sorts of covers and/or mouthpiece guards that prevent a diver using the reg without removing the cover and therefore taking a moment to think about which reg he's breathing. The gas-block system does seem like an underwater death machine. Later, JoeL > Examination of the subject's diving equipment (Figure 2) revealed that he had > been breathing the 50% oxygen/nitrogen mixture for most of the dive. Each tank > had a separate first stage connected in an unusual fashion by a two-way > switch, which the diver had had made by a local engineering shop. This allowed > the diver to switch from one tank to another rapidly. This switch supplied a > single second-stage mouthpiece. The two tanks were different colours; the > circuit from the black (compressed-air) tank was marked with yellow tape, > while the circuit from the yellow (nitrox) tank was unmarked. > The cause of death, as determined by the Coroner, was drowning after oxygen > toxicity.(5) The "shivering" movements and the biting of the tongue and > mouthpiece suggested fitting. Using a 50% oxygen/nitrogen mixture at 47 m > depth, the diver had been exposed to a partial pressure of oxygen of 291 kPa > (2.9 atm), possibly for as long as 19 min. During diving, this gas mixture > should be used only at depths less than 14-18 m (depending on the duration of > exposure). > This death resulted from several compounding problems: > > 1.The diver may have turned the switch to the unmarked nitrox circuit, > thinking he was using the circuit to the compressed air in the black tank (the > yellow label marked the circuit from the black [compressed-air] tank, not the > circuit from the yellow [nitrox] tank). Alternatively, as the two-way valve > needed very little pressure to turn, it could have been accidentally switched > from a safe to an unsafe gas mix. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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