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silent running · 14th December 2006, 02:12

Quote: (Originally Posted by dive2dive2000)

Hi Mike,

You bring up an interesting topic and some interesting points.

I don't believe your test is accurate because during an unexpected CO2 hit by the time you realise you are experiencing a CO2 hit your motor skills might be greatly reduced. I personally believe a BOV is safer and quicker than going straight to bail out If diving a FFM I personally feel a BOV is a must not an option. Being a cold water wreck diver and a PRISM user I feel I can get a sanity breath in the right amount of time from holding the ADV dn (I am not sure if all units are capable of this, on a prism your dil feed is right under inhalation CL fitting and hose to your mouthpiece, so you can get a sanity breath by inhaling crushing lung flat and depressing adv simultanisly) the only neg to this is your buoyancy can and will become negative (if done wrong then positive). Being a wreck diver I am on or near bottom or structure or near a line. If I was an avid cave diver or wall diver I would feel stronger towards a BOV just because of the buoyancy factor.

Basically what I am saying is that a BOV can and should be used over a DSV depending on your CCR and the type of diving you do.
just my PPO2

Hi Marty, I'm wrestling with the BOV issue for the Prism also. My current opinion is that it would be good to have for 2 reasons:

1) Another easy way to add dil to the loop, say during a rapid descent if the ADV whip popped off or that crude little shrader valve blocked up-redundancy

2) ADV shrader valve can't flow as much as a good reg down deep.

That being said, would you really need a whole lung full of fresh gas to bring down the CO2 level enough to gain relief? The Prism ADV being right next to the inhale hose does provide nearly instant fresh gas, without it mixing with with the gas already in the IN CL and it might still flow enough to bring down the CO2 enough to get it together. While depressing the ADV with my right hand I use my left to vent the exhaled gas through the OPV in the EX CL, bringing the CO2 down further and keeping my bouyancy the same-open loop. I've practiced this a bit and it's pretty easy, but no doubt, turning the BOV lever would be easier so I would still rather have one, if only for the dil add redundancy.

But then there's the WOB issue. How will any of the currently available BOVs work with the Prism loop? If I can add one without increasing the WOB over the stock DSV, then I'd be all for it. Otherwise, it might be foolish to add something in anticipation of a possible CO2 hit which might actually increase the chance of that happening by increasing the WOB. Tough call. Anybody have a BOV on their Prism right now?

Mike, sorry if this seems like a hijack, but I think it's still relevent... -Andy

14th December 2006, 02:12	#10 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,832	Re: Functioning with high CO2 Quote: (Originally Posted by dive2dive2000) Hi Mike, You bring up an interesting topic and some interesting points. I don't believe your test is accurate because during an unexpected CO2 hit by the time you realise you are experiencing a CO2 hit your motor skills might be greatly reduced. I personally believe a BOV is safer and quicker than going straight to bail out If diving a FFM I personally feel a BOV is a must not an option. Being a cold water wreck diver and a PRISM user I feel I can get a sanity breath in the right amount of time from holding the ADV dn (I am not sure if all units are capable of this, on a prism your dil feed is right under inhalation CL fitting and hose to your mouthpiece, so you can get a sanity breath by inhaling crushing lung flat and depressing adv simultanisly) the only neg to this is your buoyancy can and will become negative (if done wrong then positive). Being a wreck diver I am on or near bottom or structure or near a line. If I was an avid cave diver or wall diver I would feel stronger towards a BOV just because of the buoyancy factor. Basically what I am saying is that a BOV can and should be used over a DSV depending on your CCR and the type of diving you do. just my PPO2 Hi Marty, I'm wrestling with the BOV issue for the Prism also. My current opinion is that it would be good to have for 2 reasons: 1) Another easy way to add dil to the loop, say during a rapid descent if the ADV whip popped off or that crude little shrader valve blocked up-redundancy 2) ADV shrader valve can't flow as much as a good reg down deep. That being said, would you really need a whole lung full of fresh gas to bring down the CO2 level enough to gain relief? The Prism ADV being right next to the inhale hose does provide nearly instant fresh gas, without it mixing with with the gas already in the IN CL and it might still flow enough to bring down the CO2 enough to get it together. While depressing the ADV with my right hand I use my left to vent the exhaled gas through the OPV in the EX CL, bringing the CO2 down further and keeping my bouyancy the same-open loop. I've practiced this a bit and it's pretty easy, but no doubt, turning the BOV lever would be easier so I would still rather have one, if only for the dil add redundancy. But then there's the WOB issue. How will any of the currently available BOVs work with the Prism loop? If I can add one without increasing the WOB over the stock DSV, then I'd be all for it. Otherwise, it might be foolish to add something in anticipation of a possible CO2 hit which might actually increase the chance of that happening by increasing the WOB. Tough call. Anybody have a BOV on their Prism right now? Mike, sorry if this seems like a hijack, but I think it's still relevent... -Andy
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