How often do you check your SPGs?

PnL

On OC, I only checked a few times per dive as I was comfortable with my SAC rate and had a good handle on what my consumption would be.

Does the same thing happen once you get comfortable with CCR? Or do you not maintain your SAC rate due to the abundance of gas available to you? A related question to this, then, is -- does your metabolic rate of O2 consumption depend purely on a set rate based on your physiological demand for oxygen (at a given state of work), or does it fluctuate with the number of breaths you take. I would guess the faster you breath the more O2 gets absorbed by your lungs but would like to hear from those more experienced about this.

Thanks,
Paul

Digger

You would probably check your SPGs abotu the same amount on a normal dive. What you're looking at on CCR is ppO2, that's the important thing. And you should be checking that a lot.

I find myself checking the gauges a couple of times during a dive to make sure I'm not using gas fast (tends to be an indicator of a problem, but you should have noticed a problem like that well before then) and that I've got plenty of gas for the dive. Which you do on CCR.

Your metabolic rate varies very little during the dive. It will be at a normal rate most of the time, with very slight variations during periods of high workload or rest. But none that I particuarly notice ever.

Digs.

wedivebc

Most experienced Rebreather divers try to be aware of every bubble that leaves their RB. That means if there are bubbles you are not expecting then something is wrong. Unless I have a problem or become aware of gas loss I seldom check my SPG. I do practice gas loss drills and I often check O2 after doing a flush at 20ft but during the dive I just know the gas is there.

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Mark Chase

I check my SPG gauges before I get in and usualy just before the ascent to deco then on the 6m stop. I am only interested in o2 but i generaly chenck them both anyway.


I dive with CCR divers so if i hav a streem of bubbles comming from the rig i am confident they will let me know.

ATB

Mark

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Juz

5 or 6 times for each dive:

Before I drop in
On way down as I switch set point
Middle of dive
Before I leave bottom
At 6m stop (if doing a longish deco)
Before leaving 6 to hit the surface

Sounds a lot, but in reality, it just to check that the needle isn't at 0.

Juz

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divetheworld

That is absolutely text book. I might check at the 6m bubble stop on the decent, not always possible.
Nuff said.

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teksimple

I check the pressure in my spheres at the beginning of the dive. If I check them at any other time, I feel it is an unnecessary luxury and reduces my reliance on the more important tactile and auditory methods of determining gas status. The exception would be if I were accompanied by noisy open circuit divers. My policy is to always begin every dive with dil and O2 maxed, period.

At my normal O2 consumption rate, I should get at least 10 hours. Any loss of gas otherwise should and will be entirely noticeable. Yo-yo dives at near-rec depths would be the only way to exceed this rate. On big solo dives, I prefer to completely remove my SPG's altogether, as they are more of a liability to gas conservation than an asset.

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