Did Learning Rebreather Improve you SAC rate?

[rjack321]

@JackZwykle
I'm not aware of anyone trying to calculate there CCR SAC.

Wouldn't that functionally be O2 consumption?

 

[The Chairman]

My SAC/DAC has decreased with every year of diving. I attribute that more to my comfort level than anything else.

 

[JackZwykle]

Wouldn't that functionally be O2 consumption?

Not really. You can blow like a steam engine and simply not use much more O2 than baseline for the given effort. What we discussed and I tried to point out (and was confirmed by the poll) is that CCR diving does (and should in my limited opinion) raise instinctive SAC rates.
You are a part of the CCR unit, not just the user. You're the loop pump after all!
Run the pump too low and you can run into all kinds of trouble. Trouble with that trouble is no one can calculate there and then how much exactly is the trouble.
So best to breathe a lot.

The question what to do with those numbers on BO is connected as the PO reminded me.
I take those high numbers, add 50% and I know I'm realistically able to BO myself and another diver on the same gas.
As another diver on my team is a diver I would really like to be able to assist, I like that policy.

My optimal but still realistic SAC when I calm down and focus on saving gas is roughly 3 times lower than what I do instinctively and use for calculations. So I know I have plenty for myself and another diver in distress. Makes the dives so much more relaxed.
Even if a bit encumbered, but that's nothing that a bit of a DPV can't help with.

The point I was trying to make is that trying to lower the instinctive SAC is dangerous for CCR.
And (in my very limited opinion for which I am fully prepared to be whipped) if you notice your instinctive BO SAC dropping when diving on the CCR - you might want to address that.

I am quite happy that my uncontrolled SAC went almost 3 times higher. I can still focus during a real BO and save the gas, although I don't have to. I plan for unthinking BO operation if I have other problems to deal with.

 

[JackZwykle]

My SAC/DAC has decreased with every year of diving. I attribute that more to my comfort level than anything else.

Oh Gods... here comes the whipping...

 

[rjack321]

Not really. You can blow like a steam engine and simply not use much more O2 than baseline for the given effort. What we discussed and I tried to point out (and was confirmed by the poll) is that CCR diving does (and should in my limited opinion) raise instinctive SAC rates.
You are a part of the CCR unit, not just the user. You're the loop pump after all!
Run the pump too low and you can run into all kinds of trouble. Trouble with that trouble is no one can calculate there and then how much exactly is the trouble.
So best to breathe a lot.

The question what to do with those numbers on BO is connected as the PO reminded me.
I take those high numbers, add 50% and I know I'm realistically able to BO myself and another diver on the same gas.
As another diver on my team is a diver I would really like to be able to assist, I like that policy.

My optimal but still realistic SAC when I calm down and focus on saving gas is roughly 3 times lower than what I do instinctively and use for calculations. So I know I have plenty for myself and another diver in distress. Makes the dives so much more relaxed.
Even if a bit encumbered, but that's nothing that a bit of a DPV can't help with.

The point I was trying to make is that trying to lower the instinctive SAC is dangerous for CCR.
And (in my very limited opinion for which I am fully prepared to be whipped) if you notice your instinctive BO SAC dropping when diving on the CCR - you might want to address that.

I am quite happy that my uncontrolled SAC went almost 3 times higher. I can still focus during a real BO and save the gas, although I don't have to. I plan for unthinking BO operation if I have other problems to deal with.

disagree.
O2 consumption and CO2 removal are the only relevant "SAC-like" metrics on CCR. Since most units can't measure CO2 at all and those that do have a CO2 alarm dont have continuous loop monitoring anyway, the only thing we can measure is O2 consumption.

Nobody cares how fast the loop gas is going round and round except for the workload going up just breathing. But if you O2 consumption rise or falls that impacts your ability to stay underwater the exact same way OC SAC rates influence your dive times.

 

[JackZwykle]

disagree.
O2 consumption and CO2 removal are the only relevant "SAC-like" metrics on CCR. Since most units can't measure CO2 at all and those that do have a CO2 alarm dont have continuous loop monitoring anyway, the only thing we can measure is O2 consumption.

Nobody cares how fast the loop gas is going round and round except for the workload going up just breathing. But if you O2 consumption rise or falls that impacts your ability to stay underwater the exact same way OC SAC rates influence your dive times.

Just conversationally - if SAC drops to say 10, do you think the whole system still works well, especially in cold water (hint)?
Will sofno get enough CO2 rate to stay hot (and effective), will lungs not retain CO2 leading to blood CO2 rise? At certain SAC level (that you can't guess) won't it start failing to work in crucial components? (Scrubber and lungs)
Really? SAC (more correctly breathing pattern) is not important, only O2 consumption?

Or similarly - O2 is still consumed, CO2 is removed, but NOT FAST ENOUGH because of breathing pattern. Either through lung retention or scrubber thermal block.
Is that still ok?

Anecdotally and logically (and we don't have any solid research outside of that) - turning the loop pump down past an unknown limit causes all kinds of unexpected and weird trouble.
So - do care about on the loop "SAC", do breathe a lot and especially deep.

In shorter form - you can absolutely breathe yourself into dark narc and still have O2 consumption and even CO2 removal all right.
I've experienced that although I can't provide evidence.

Dark narc killed more people that I think is publicised.

Stay safe.

 

[Underwater Tourist]

Just conversationally - if SAC drops to say 10, do you think the whole system still works well, especially in cold water?

This immediately made me think about petite ladies with low sac rates diving CC in cold UK & Nordic waters

I haven't read any anecdotal stories about them having more issues with the scrubber compared to men

So I would guess if "a critical SAC level for CCR operation" exists, it might be too small to have a practical effect

 

[rjack321]

Just conversationally - if SAC drops to say 10, do you think the whole system still works well, especially in cold water (hint)?
Will sofno get enough CO2 rate to stay hot (and effective), will lungs not retain CO2 leading to blood CO2 rise? At certain SAC level (that you can't guess) won't it start failing to work in crucial components? (Scrubber and lungs)
Really? SAC (more correctly breathing pattern) is not important, only O2 consumption?

Or similarly - O2 is still consumed, CO2 is removed, but NOT FAST ENOUGH because of breathing pattern. Either through lung retention or scrubber thermal block.
Is that still ok?

Anecdotally and logically (and we don't have any solid research outside of that) - turning the loop pump down past an unknown limit causes all kinds of unexpected and weird trouble.
So - do care about on the loop "SAC", do breathe a lot and especially deep.

In shorter form - you can absolutely breathe yourself into dark narc and still have O2 consumption and even CO2 removal all right.
I've experienced that although I can't provide evidence.

Dark narc killed more people that I think is publicised.

Stay safe.

What are you going on about? SAC is "surface air consumption"
There is no "consumption" on a CCR beyond O2 in and CO2 out. The depth or rate of ventilation is not consuming anything

 

[JackZwykle]

What are you going on about? SAC is "surface air consumption"
There is no "consumption" on a CCR beyond O2 in and CO2 out. The depth or rate of ventilation is not consuming anything

I am MOD2, I kind of know that. We're bored and discussing fine points (nitpicking) about effects of CCR experience on instinctive breathing patterns and BO SAC calculations.
Personally I'm not in love with a SAC acronym (and A LOT of other terminology, one can see that pioneers of scuba were not terminologists ), VR would be better and more sexy (Volumetric Rate), as it's depth independent really and doesn't have "surface" in the name about a diving term.

 

[JackZwykle]

This immediately made me think about petite ladies with low sac rates diving CC in cold UK & Nordic waters

I haven't read any anecdotal stories about them having more issues with the scrubber compared to men

So I would guess if "a critical SAC level for CCR operation" exists, it might be too small to have a practical effect

Hah. Now that's an interesting point...

Counterpoint - they are very unlikely to produce enough CO2 to overload that cold, under-efficient scrubber if they're that tiny.
I don't have that problem, the wifey does not suffer from tinyness at all.

Yeah, she's not on these boards of course.