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The most sophisticated FFM gas switching rig I've seen is Greg Zambeck's (shown in a photo in Deep Tech #2). In addition to two 2nd stages fitted onto an aga mask, he's come up with a safe, redundant switching scheme. For use with an exo, i've appropriated some similar ideas. A stainless or brass sched. 80 T or X with 1/4 - 3/8 npt thread makes an excellent block. Ball valves switch reliably--but perhaps too easily. For this reason, all gas switching should be done with deso (double end shut-off) quick connects--as used for bail out bottles for hose diving. with the block in front (and in view), all gas switches are as deliberate as swapping a regulator into your mouth from a new stage. All connects should be tagged for MOD. A valve can still be useful as a back-up to switch between 1st stages on back (bottom) gas for redundancy, but they should not be used for gas switching due to the probability of mix-up, leak-thru, or accidental switch. As back-up, a mask (worn on neck) and regs. should be available for all stages. A deso can be placed in-line in a conventional regulator hose to allow snapping the 2nd stage onto different stages. you can keep the 2nd stage snapped in or in a hip pocket. Make sure your deso is rated for a flow of Cv > 0.5 for deep dives. You can buy hoses and fittings from outfits like DECA in santa barbara or Amron in San Diego. Ultra techie it is...but bailing the ffm for deco (or using the ffm exclusively for deco) is unsatisfactory in many instances. regards, em _____________________________________________________________.sig Eric Maiken email: eapg243@ea*.oa*.uc*.ed* Dept. of Physics o: 714 824-6621 U of California fax: 714 824 2175 Irvine, CA 92715-4575
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