First rebreather choice

[RainPilot]

If you dont have MAV you can dil flush by pressing the purge on the BOV while it is in CC mode. This is the ADV mechanism. That is if you dont do a "lung flush" by exhaling all the way through your nose then inhale from loop and repeat so the ADV is flushing (obviously not a good idea in all situations but it is an option).

Setpoint can be adjusted on the paddle-equipped units but not during a dive. The way the Poseidon handles shallow and deep set points is totally different from other manufacturers so it isn't necessary to adjust during the dive (if you agree with their paradigm) especially for rec CCR training. When in doubt, bail out. If you need to stay on a loop, that does call into question bailout gas planning.

Obviously each diver has their own set of priorities and desires in a CCR so we have multiple units that are the "best" for different divers doing different dives.

 

[rjack321]

looking at TDI standards, dil flush is required, but SCR/Open Loop are not mentioned in the standards. There is a blurb about any additional skills required by the manufacturer so Leon must have added those *good additions*.

My Meg TDI MOD1 was in 2015 and SCR was specifically called out as "no numbnuts carry enough BO".
Dil flushing was obviously covered in a couple of scenarios.
Returning to the loop after bailing was covered - but in the context of "it better be a simple, known, easy fix" otherwise just use the BO, its what you bring it for. The attitude of troubleshooting in order to stay on the loop was highly discouraged (at least at the entry level).

 

[doctormike]

@doctormike SCR is absolutely critical if you intend to cave dive... Whether you have enough bailout or not. I'd argue it's more useful than breathing open loop, though breathing open loop is the first step to diving SCR, so there's that

Never have gone beyond cavern, and never will, but I’m always interested in learning. I think we are using different definitions of “enough bailout”.

SCR certainly gives you something that open loop doesn’t, but open loop is really a short term thing. Unless you have dilout and are just using your dead CCR as a second stage, right?

 

[rjack321]

Never have gone beyond cavern, and never will, but I’m always interested in learning. I think we are using different definitions of “enough bailout”.

SCR certainly gives you something that open loop doesn’t, but open loop is really a short term thing. Unless you have dilout and are just using your dead CCR as a second stage, right?

Plus SCR does not work for sh*t if you are ascending. More like a hail mary if you are ascending 2-3+ ATA on dil before you get to a deco gas (or the surface).

My Meg NSS-CDS Cave CCR crossover course did not extensively cover SCR at all *shrugs*
My Kiss MOD1 crossover covered SCR ad nauseum. But then again if you use 32% dil its perfectly plausible to swim around at a constant 90ft depth on SCR. Ascending from a 250ft wreck on 10/50 to get to your 70ft bottle? SCR is more likely to kill you than help.

I don't consider SCR an essential skill - it can be something between easy and suicidal depending on the dive.

 

[helodriver87]

Plus SCR does not work for sh*t if you are ascending. More like a hail mary if you are ascending 2-3+ ATA on dil before you get to a deco gas (or the surface).

My Meg NSS-CDS Cave CCR crossover course did not extensively cover SCR at all *shrugs*
My Kiss MOD1 crossover covered SCR ad nauseum. But then again if you use 32% dil its perfectly plausible to swim around at a constant 90ft depth on SCR. Ascending from a 250ft wreck on 10/50 to get to your 70ft bottle? SCR is more likely to kill you than help.

I don't consider SCR an essential skill - it can be something between easy and suicidal depending on the dive.

I'm far from experienced on any rebreather, but it seems like it's a tool for padding your bailout margin for linear penetrations. Basically, if you're gonna spend a lot of time at or near your planned depth on the way to the door, you can build a larger bailout safety margin by doing it.

 

[JohnnyC]

The big boon of SCR is that you can maintain your bailout reserves. If you were to carry enough bailout to cover your own gas, plus reserves, plus unknown emergencies, plus buddy reserves, plus, plus, plus, plus....... you can see how a 500ft. penetration dive could theoretically require 8 stages provided there were a couple navigation choices to be made.

To be clear, going SCR sucks. It's annoying to deal with, it's task loading, and it's somewhat of a short-term solution, but the closer it gets you to the exit before you have to switch to the "rapidly dwindling" gas supply, the better. It's not applicable in all situations, and it's a bad choice in others, but in several situations, it's a viable skill to use. It's not a "Type R" type of skill though.

 

[tbone1004]

Never have gone beyond cavern, and never will, but I’m always interested in learning. I think we are using different definitions of “enough bailout”.

SCR certainly gives you something that open loop doesn’t, but open loop is really a short term thing. Unless you have dilout and are just using your dead CCR as a second stage, right?

What I meant by the open loop concept was that if you can do SCR breathing, open loop is just SCR with 0 breaths. Same technique of inhale against the adv or mav to empty the counterlung.

SCR still means carrying enough bailout, but it means that your bailout reserves are a LOT better if you can use it like @helodriver87 and @JohnnyC said. Where you may only have 1.5x bailout at the back, SCR could give you 8x or more reserves in the back. Gives you time to wait out a siltout, take your time on the exit if you really need to, spend extra time looking for your buddy, etc etc etc. Sure it's an almighty pain in the ass, but no different than feathering a valve in sidemount, it gives you options

@rjack321 how did your cave CCR course not cover SCR? I swear my buddy and I spent like 80% of the dives on SCR.

 

[wedivebc]

What I meant by the open loop concept was that if you can do SCR breathing, open loop is just SCR with 0 breaths. Same technique of inhale against the adv or mav to empty the counterlung.

Open loop is the fastest way to get to a known, breathable gas as an interim to getting a more sustainable source of breathable gas.

 

[rddvet]

I’m surprised scr isn’t more commonly taught. I was taught in both my mod 1 course and cave ccr. I also don’t find scr mode very difficult or taxing at all. Sure it’s some added task loading when you’re already task loaded, but knowing I’m extending my bailout by large factors is calming.

 

[rjack321]

@rjack321 how did your cave CCR course not cover SCR? I swear my buddy and I spent like 80% of the dives on SCR.

Leon thinks SCR is a way for people to excuse carrying inadequate BO and he discourages his approved instructors from teaching it (on the Meg). Its fine on a linear penetration with a decent ppO2 in your dil. I spent stupid hours on SCR on my kiss crossover with 32% dil/BO.

But like I said, going up from a wreck dive on 10/50 its going to be more problem than help. And really what problems is SCR actually for? Dead monitoring/electronics and out of O2. If you flood your unit or have CO2 or pretty much every other issue you're not going SCR anyway. Thinking you can "always go SCR" is not a good mindset at all.