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Hi all, We all know that air is not the ideal gas for many dives. At shallower depths, Enriched air Nitrox offers advantages in terms of reduced Nitrogen loading. What about the deeper ranges where the problem is that of Oxygen toxicity ? The conventional solution at these depths (50+m) is to switch to gas mixtures such as heliox and trimix in which the FO2 is reduced. Has anyone tried an alternative of Reduced air Nitrox ? By this I mean air to which *Nitrogen* has been *added* to reduce the FO2. At first glance, the answer seems to be that you wouldn't want to do this as the narcosis would be worse. However, recent work seems to have shown that Oxygen is equally narcotic as Nitrogen and I therefore suggest that altering the ratio of Oxygen to Nitrogen in either direction will not affect the narcotic potency of the resulting gas. Why is this interesting ? I suggest there are 4 reasons: - People have pushed air to incredible depths and seem to have coped with the resultant narcosis (452 feet is the current record I think). - Reducing the Oxygen fraction will decrease the risk of Oxygen toxicity over using air to the same depth. - Mixing and decompression calcuations are much simpler with only a single inert gas component. - Nitrogen is *MUCH* cheaper than Helium! I realise that you will pay a decompression penalty in increasing the inert gas fraction, but you have to pay this anyway when you reduce your Oxygen fraction (in Trimix/Heliox diving). Has this idea been tried or researched in the past ? Or is there something obvious I have missed in this ? [An interesting aside: one way of testing for the narcotic potency of oxygen would be to try switching between say Air and 5%O2/95%N2 mix at 50m. I presume something like this was done in the research into this issue.] Cheers, David. ______________________________________________________________________________ David Giddy, | Voice: +61 3 253 6388 Telstra Corporation, | Fax: +61 3 253 6144 P.O. Box 249, Rosebank MDC, 3169, AUSTRALIA | Internet: d.giddy@tr*.oz*.au* ------------------------------------------------------------------------------
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