Open, Semi or Closed-Circuit?

[Meng_Tze]

Both SCR and CCR have far more efficient gas usage over OC.

SCR does that with exhaling every x number of breaths and with a fixed FO2 (of course you can plug in different gases for different MOD's, but for simplicity let's stay with one gas). This fixed FO2 gives variable PO2 during the dive. Basically SCR extends your gas multifold. SCR usually does not have electronics and is a simple system to manage. There is not much that can break.

CCR is a closed system that only replenishes the metabolized O2. There is diluent on board to also make up volume, but once you have set a volume, you only use O2. The system works on constant PO2. This results in different FO2 for different depths. You basically mix gas on the fly for a given depth for a given PO2. The CCR is the most efficient in gas usage but uses electronics. Electronics and water have a strained relationship.

 

[Thalassamania]

SCR's are, inherently, a design that trades capability for risk. If you are interested in keeping your risk to a minimum, and the diving you want to do is within the capability of an SCR, that's what I'd recommend to you. Of course, its never quite that simple.

 

[wedivebc]

There is not much that can break.

.

Except a plugged orfice will kill you. Without PO2 monitoring you will probably not even know if it happens during a dive.

 

[wedivebc]

Really? I guess that 12:1 - 18:1 gas extension is just whistlin dixie!
.

What SCR has anywhere near that efficiency?

 

[PerroneFord]

What SCR has anywhere near that efficiency?

You know, when I wrote that, I was thinking... Am I remembering right? Just checked and it is 10:1. My mistake and thanks for catching that.

 

[nereas]

SCR's are, inherently, a design that trades capability for risk. If you are interested in keeping your risk to a minimum, and the diving you want to do is within the capability of an SCR, that's what I'd recommend to you. Of course, its never quite that simple.

Of course, to virtually eliminate certain CCR and SCR risks, simply stick with open circuit.

If one does not require the range of a CCR, then simply do not go there at all, and then the unknows of the CCRs are eliminated.

CCRs offer convenience, sure, but convenience alone is simply not worth added risk.

 

[Mr.X]

The main thing that you are going to need with a CCR is a really good CCR-buddy, who watches you, and you he/she, every second. Because at any second, anthing can go wrong with these units.

Therefore if you are a solo diver, then CCRs are completely out of the question. This is how people die, by diving solo with a CCR.

SCRs make no sense at all because you have all the same liabilities as with a CCR and none of the CCR benefits. But if you go the SCR road, then similarly make sure you have a really good SCR-buddy.

How did you come to these conclusions? I've been diving RB's for a while and a lot of your fluff-stuff just doesn't pan out.

X

 

[rjack321]

1) PADI/DSAT doesn't have any rebreather training at all. Nor any cave training, although they do have a cavern course. How and why are you interested in them??

2) with less than 50 dives the OP should really just go diving for awhile before talking about RBs and technical training.

 

[Thalassamania]

1) PADI/DSAT doesn't have any rebreather training at all. Nor any cave training, although they do have a cavern course. How and why are you interested in them??

2) with less than 50 dives the OP should really just go diving for awhile before talking about RBs and technical training.

Agreed.

 

[nereas]

How did you come to these conclusions? I've been diving RB's for a while and a lot of your fluff-stuff just doesn't pan out.

X

So I take it that you are solo diving with your CCR and now you want some sunshine about how that is not a problem?

If you want to be a good, safe solo diver (almost a contradiction in terms, however) you really need to be on open circuit. Then there is "less" that can go wrong. And then when something does go wrong, hopefully you can see it coming and deal with it, rather than be knocked unconscious by surprise, as with a CCR.

Just because you have been getting away with "doing something" for a "long time" does not make you a rocket scientist. Nor safe at it.