> Yes, but an electronic RB is the perfect killing machine.  If OC
> fails, then
> it just won't give you gas.

That seems like a "perfect killing machine" for a person underwater - having
no gas.  If you run out of gas on a rebreather, you have like 30-45 minutes
to solve the problem. But, I understand your point - which is a point I've
made for years:  OC failures tend to be self-evident, whereas:

> There are many more insidious ways
> you can die
> with an electronic RB.

Actually, there are really two insideous ways you can die with an electronic
RB:  hypoxia, and hyperoxia.  Hyperoxia is arguably even more insideous with
open-circuit nitrox than with electronic RB's (albiet perhaps easier to
avoid, because you need to check the mixture only once), because the OC
nitrox has no real-time sensors that can warn you of the wrong mix.  The
window of life-sustaining PO2 ranges from about 0.15 to 1.5 (actually, it's
hard to draw a line at the high end, because that number is so incredibly
variable - so I'm being very conservative) - a factor of ten.  Physics
requires that SOMETHING has to happen for the PO2 to move up and down this
scale (dpeth change, gass addition, O2 consumption by the diver). The
training comes into play for allowing a diver to understand what factors
cause the PO2 to move up and down this scale, and therefore indirectly
recognize when the PO2 may be changing in its range - with or without
working sensors.

Aloha,
Rich

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