floridagirl92
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I was wondering if entering the water in open circuit, making the descent using OC gas and then switching to CC would work well? It is easier to descend that way for me. Any thoughts? Thanks.
Rebreather descent on Open Circuit?
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Dsix36
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Although it is possible, I do not think it is necessarily the best way. You must make sure the ADV is working properly before attempting this. You will also have to make sure that you verify the loop PO2 prior to going to CC.
Putting the DSV in your mouth and getting water because it flooded on the descent would not be a good thing.
If your descent requires a lot of hard work and your breathing rate is highly elevated, then perhaps a OC descent is called for but otherwise probably not.
Putting the DSV in your mouth and getting water because it flooded on the descent would not be a good thing.
If your descent requires a lot of hard work and your breathing rate is highly elevated, then perhaps a OC descent is called for but otherwise probably not.
With my GEM, I can breath the loop on descent from 0, even be on the loop on the surface (but vigorous monitoring of PPO).
But if I know I'm going to be hard on the loop, I'll do OC until 20ft, then switch to the loop (or when effort drops off)
But if I know I'm going to be hard on the loop, I'll do OC until 20ft, then switch to the loop (or when effort drops off)
I descend on the loop. Why consume gas intended for emergency procedures when you don't have to? Seems foolish.
Why is it easier?
As a rebreather instructor - why would you descend on OC and switch to CC at bottom? Stay on the loop, monitor PO2 constantly and do a intelligent descent. If you've got to fly down to the bottom better have some experience under your belt and a reason for doing it. Especially on CC.
billgraham
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I think the OP is probably worried about spiking the PPO2, but it's a bad idea for the reasons given above. Also, on the chance that you missed something on your checklist, you might hear a gurgle on a slow descent on the loop, and be able to turn it and go fix it instead of putting the loop in your mouth on the bottom and having it flood there.
DevonDiver
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If it's easier... why not do the bottom portion on OC also? 
I would not say it's any safer... if you were to have a malfunctioning unit, as opposed to finding out on the surface (or near the surface) you would only find out at depth. IMO that not where you want to find out your scrubber is wet and experience a CO2 Hit.
if you want Easier, I would add a Dill add valve on your CCR, this makes descents and dil flushes easier and safer, I added one on my KISS and if I could only do one modification to my unit, this would be it.
if you want Easier, I would add a Dill add valve on your CCR, this makes descents and dil flushes easier and safer, I added one on my KISS and if I could only do one modification to my unit, this would be it.
Still have to perform your linearity test at 6m on the loop... After, flush the loop down to .7-.8 with dil and you are good to go. As long as you don't race to the bottom, maybe worst case you flush with a little dil.
Are you performing a cell linearity test at 6m?
Rebreather diving is not a spectator sport.
Are you performing a cell linearity test at 6m?
Rebreather diving is not a spectator sport.
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