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On Sun, 17 Apr 1994, Rick Fincher wrote: > > One thing I was wondering. If you are going to all the trouble and > expense of using non-air mixes why use Nitrox at all instead of > Trimix or Heliox? > > It seems to me that you would get even more bottom time or greater > dcs protection without the added risk of O2 toxicity by using those > mixes instead of Nitrox. > Tri-Mix is best to avoid when possible because for all but the longest dive durations, it incurs a larger decompression penalty than Nitrox. This is because you must sum the nitrogen and the helium in the body's tissues when figuring decompression. This is a particular problem in the slow tissues where the M-values are low. The slow tissues rapidly load up with helium, and once a slow tissue is heavily loaded, it takes a long time to get the gas out, particuarly if there is more than one gas in the tissue. > Is Nitrox that much cheaper? Is special equipment needed for Trimix > that is expensive? Helium is very expensive. Oxygen is cheap. This gives Nitrox a big price advantage. > Are there other hazards of Trimix use? Yes, but only with mixes intended for depths well beyond those at which Nitrox is usable. > Does Trimix extend NDC time or do you just have to blow off the helium > etc. instead of Nitrogen? Common Trimix mixtures reduce NDC time compared with Nitrox or Air. - Jody Svendsen (MiG Technologies)
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