OC / CC DSV, Which one and why?

[divetheworld]

Originally Posted by nigelH

Good point. Naturally I came to it from the two handed APV shut off mouthpiece so I expected to use both hands. One handed operation would be nice but I'd probably twist it off the mouthpiece if I did that too often.

you know guys, if you dont like them I'll take them off your hands.
Cheap too!!

[narked at 90]

Originally Posted by divetheworld

Nemotech do a good one at a reasonable cost. Be prepared to wait for it.
http://www.master.pl/~nemotech/menu%20gb.htm

Ask John (Narked at 90) for his opinion, I think he has one now.

b
i would love to coment on the nemotech oc/dsv but im still waiting! it's been 3mounths now and i expect it any day now.....................................
so all i can say is the reason i went for it
the kiss dsv's hose comes from the right side but i wanted from the left and the menotech is interchangerble from side to side,
the kiss dsv has the valve nob underneth and the second stage on the front where the nemo have the nob at the front which i was thinking would be better for a buddy if i had passed out for some reason as they can see which way to turn it with out to much thinking about it.
the nemo dsv comes from euroup so you dont get hamerd with extra tax and workes out cheaper.
and they make the dsv to fit your rebreather hoses not just make adapters

kind regards john routley

[Pierre Farrugia]

Sorry if this is a stupid question, what are the benefits of using an OC/CC DSV ? Does a flood in either system can effect the other ?

[narked at 90]

Originally Posted by Pierre Farrugia

Sorry if this is a stupid question, what are the benefits of using an OC/CC DSV ? Does a flood in either system can effect the other ?

hi pierre the ability to swap from ccr to o/c and back again with out removing your mouth piece i think is off a massive benifet if you read some of the problems when you get a co2 hit,
things like your breathing rate is so high that you can not stop breathering for anouth time to come off the loop.
or the first real indication of a problem is you dont hav e the energy to do much about it......just maybe turn a knob? or if with a buddy they could do it for you with out you drowning!
it's another way to add dill to the loop- i dont have a manual add on my unit!
i am fitting mine to my FFM so it's also a way to purge my mask.
im shore i've mist a few things! but for me on my unit its a big plus but i guesse JB will think me a wuse
kind regards john routley

[schford]

I definatly hear what your saying....but there is an argument that....

Why would you want to go off the loop? The only reason the argument goes is that if your loop integrity is shot...

If it was a Co2 hit you would be much better off switching over to Open Loop, eg immediatly flushingyour loop with fresh dilutent and for every breath through your mouth the exhale goes out of your nose...Much quicker than going to OC and just as quick if not quicker than fiddlign with a switch...

PS yup you need a manual add button though!

[PrettyFishies]

Stuart - Open Loop can be done via ADV, you don't need a manual add.

For interest open loop isn't necessarily always the best solution, if using a hypoxic dil on a unit with no electronic setpoint control, the ADV will fire in hypoxic dil and lower PPO2 rendering closed circuit decompression schedule invalid on deeper dives.

If loop integrity is compromised, better to bail out and switch OC bailout tables. Or VR3 OC.

Regards

AnneMarie

[Brass Monkey]

Originally Posted by schford

I definatly hear what your saying....but there is an argument that....

Why would you want to go off the loop? The only reason the argument goes is that if your loop integrity is shot...

If it was a Co2 hit you would be much better off switching over to Open Loop, eg immediatly flushingyour loop with fresh dilutent and for every breath through your mouth the exhale goes out of your nose...Much quicker than going to OC and just as quick if not quicker than fiddlign with a switch...

PS yup you need a manual add button though!

After reading about people who have had a CO2 hit it sounds like it's almost impossible to imagine coming off the loop. At best you might be able to turn a knob on an OC/CC DSV otherwise it's good night. If you flush your loop with DIL you still have to work that around as it is fed in to the bottom of the lung. The best way to say on the loop would be to use the ADV if you have one. To me an OC/CC DSV is a very useful piece of kit and one I will be buying soon. It's been posted on the Inspiration list that AP are working on their own. If this is true it says it all. Thanks for the replies so far guys, keep them coming the more information you post the better for everyone.

Dave.

[Brass Monkey]

I was a few sheets to the wind last night when I made that last post. After reading it this morning I have to say that Stuart has a good point. I remember reading a report about a guy who got a CO2 hit and could not do anything, he just lay on the bottom almost paralyzed. He said that the only thing he could manage was to exhale through his nose and let the ADV inject on the inhale. After a couple of minutes his head cleared enough to allow him to move around and sort himself out. It would seem to depend on the individual and the extent of the hit. On the other hand there’s a lot people who have had hits and could have operated an OC/CC DSV if they had one. As it was they couldn’t bring themselves to come off the loop and did not have the presence of mind to go “Open loop”. I’ve never experienced a hit and hope I never will but the option to turn a lever and be straight on a known gas is one I definitely would like to have.

Dave.

[The Purist]

Originally Posted by schford

I definatly hear what your saying....but there is an argument that....

Why would you want to go off the loop? The only reason the argument goes is that if your loop integrity is shot...

If it was a Co2 hit you would be much better off switching over to Open Loop, eg immediatly flushingyour loop with fresh dilutent and for every breath through your mouth the exhale goes out of your nose...Much quicker than going to OC and just as quick if not quicker than fiddlign with a switch...

PS yup you need a manual add button though!

In my case I was already doing this as I'd lost loop volume and so was pulling/pushing Dil with every breath. My physiological reaction to CO2 seems to be a sense of rising irrational panic - at the conscious level I was fully aware what the issues were and what needed to be done, but was getting an increasing primal urge to just rip the kit off and bolt for the surface. There was undoubtedly a huge subconscious bonus from just flipping a switch (takes less time than a full Dil flush) and knowing that what I was breathing was 'safe gas'.

Would be interesting to find out how many of these opinions come from people who've experienced unplanned CO2 hits - certainly changed my perspective!

[Duncan Price]

I've had a few CO2 problems due to diving with a pissy small scrubber or over working. Have either gotten off of loop or went open loop. Everybody react differently to CO2 - I found that if I didn't feel right then there was a problem. A fair amount of paranoia keeps you alive.

Incidentally, I have had to unlearn a few things that I do whilst on OC. When tying knots or writing notes underwater on OC I tend to hold my breath so that the exhaust bubbles don't disrupt things. On CC it is bad to do this because when you breahe out you bung in a bigger slug of CO2 and give yourself a transient hit. Keep breathing slow and steady.