Incident on the surface - mCCR

caveseeker7

Thanks for the post, lucky you noticed you were getting sleepy.
Shows the importance to make sure you're ready to give support,
which includes insuring all systems are a go, and stay that way.
Not as easy on a manually controlled system, something to keep in mind.
Good of you to look out for a member of your team.

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Stefan



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jkaterenchuk

Glad everything worked out and you posted this valuable lesson for all to learn. Being relatively new to diving the Kiss Classic as I was reading your post it occurred to me that you injected O2 and breathed in to trigger the ADV. I am not sure what my instinctive reaction might be in the same situation but would it not have been better to immediately turn the knob on the BOV and be on OC? Then your lungs would have had good air faster than sucking it thru the loop. Am I overly concerned that if your PO2 display was reading that low that the air you inhaled to trigger the ADV might have been even lower in O2 content? Maybe too low!

I wonder what others have done in this same situation?

John

Hk101gr

Thanks for sharing. Very thorough yet simple analysis.
Incidents like these expose the weakness of mccr's near the surface and the great care needed in their operation.
It also got me thinking that maybe hybrids are the way to go in the development of future ccr's...
An orifice or a needle valve with a solenoid as backup/parachute could make incidents like these highly unlikely.It has been discussed extensively yet hasn't been implemented but to a couple of systems. I wonder why...

Dive safe
Dimitris

rewrites

Excellent report which illustrates just how quickly these things develop. Also highlights the need to be 'in tune' with what 'normal' is for your own body.

With regards your daughter not helping, I have to say she probably did the right thing. If she felt she could have helped, I'm sure she would have and would have been a useful pair of hands. If she tried to help without feeling competent/confident to do so, then she could just as easily have ended up being another potential casualty and added to the existing problems. Perhaps a resuce diver course/training of some kind is what she needs next.

Glad you all came out ok.

PH

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Marc

Couldn't agree more with John...I mean thanks for sharing your story and glad that nothing serious happened but I think the bottomline in general should be: "get the f*** off that loop" when you get a reading like that. Many others may have gotten to sleep already..
With the BOV fitted as standard bailing out to OC is too easy on the KISS...I've actually just gone to OC mode a couple of times on the surface at the end of a dive when I felt I had to work hard and couldn't be stuffed checking/maintaining a high pO2

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Classic KISS #271

brockbr

VERY, VERY Good Point.

Actually, the very direct feedback I got from my instructor/friend was:
"What the heck were you trying to do, conserve ambient air?" meaning I could have just as easily closed the DSV and removed the loop from my mouth altogether - No OC, no BOV, just shut it down.

His point was that I shouldn't have been on the loop once this started - I could have switched to OC or closed the DSV prior to making ANY move

All very valid points, and in the future, I will not let it be a problem by switching to OC if I'm on the surface for any amount of time.

brockbr

One other thing I wanted to point out. I don't know what difference this makes, but both myself and my instructor thought that the pO2 of 0.09 was VERY damn low and surprised I noticed it and responded.

We wondered if my running has anything to do with it - I run every day with my shortest distance being 4 miles (6:50 pace) and the longest being 9 miles (7:10 pace). I've run multiple marathons (the last one in 3:40), but run to stay in shape (not to be competitive).

I wonder what effect my cardio conditioning has as it applies to diving?

For example, when doing my original CCR training, we did a hypercapnia exercise to demonstrate what it felt like. It felt like the same thing that happens after mile 20 or so during a marathon and you pick up the pace - You just can't breathe (co2 retention), your heart-rate goes up, and you have trouble ambulating.

Makes me think I need to run more

Gill Envy

I applaud the diver for halting this chain of events in time.

something Dave Sutton wrote a while back really stuck in my mind. He mentioned that people are too afraid of O2 and are too reluctant to use it. He mentioned being quite liberal with it on ascent and in the shallows, something I have taken to heart as it seems that the biggest common denominator is hypoxia.

since picking up manual CCR diving, the school of livable consequences has taught me to lay on the manual 02 add on a regular basis as a matter of course in the shallows.

In this case i would have laid on the o2 and then cross checked my po2 on my HUD with the po2 on my handset, but I can see logic in having the dilluent be the default as it's more likely to give you a breathable gas at the surface and at depth. If you are going to leave one thing to reflex I can see why we are taught to go with a dilluent flush.

The one thing I concluded from the "oh so wonderful" discussion on HUD design is that mCCR's in particular really need real time po2 on the HUD and that the color of the lights are not so critical because you are always interpreting the real number rather than expecting an alarm to allert you that something is wrong (or in this case, getting in the habit of ignoring it). Set point has become an optimal range rather than a single point for me. I keep it up about as high as I can at or near the surface with regular, liberal pushes on the manual o2 add button (.6-.9) and then bump it up as it becomes easier as I go deeper (1.1-1..4).

And to be clear, I don't think mCCR's are "safer", it's more that they engender a school of livable consequences where it appears that pretty consistently such events are near misses rather than fatalities. I think it's because the diver is forced into a pattern of habitual po2 monitoring, being much more likely to react in time even when distracted (in this case, the last possible second still counts). With each screw up or near miss the diver is compelled to ramp up the monitoring interval, entraining a monitoring interval that actually relates to necessity.

When I owned and dove the evolution, I never really knew when I was monitoring enough... the question on my mind was always, when's the system going to fail, not when am I going to fail the system. When I felt relaxed, I'd do it less, when I felt a little nervous, I'd do it more and nothing could be more erroneous. Conversely the more relaxed I became, the more prone to error I was.

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Gill Envy

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ScubaDadMiami

A lot of food for thought here. Glad you are okay. Greenworthy IMHO.

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Howard Packer
IANTD CCR Instructor
Miami Beach, Florida
CCRDiveTraining.com

brockbr

I've been asked about my HUD, so I wanted to respond to that:

I do have a C2R HUD on my Classic KISS. This HUD uses 2 LED's. Green for pO2, and red for Decompression.

Green Slow Flash = Low pO2 (.2 or more under set point)
Green Solid - Within .2 of set point (high or low)
Green Fast Flash = High pO2 (.2 or more over set point)

Red relates only to deco and stops.

I generally run with a 1.0 set point. This means that on entry to the water, it is difficult to get a 1.0 at the surface, and for the first 3m or so. This means the LED is flashing Green Slow on initial entry.

The VR3 supports multiple set points, and I started out by diving a .7/1.0. But even a .7 suffers from the same problem - Hard to maintain .7 at the surface, so either way, the indications is a Green Slow Flash. This really serves as a reminder to check, check, check your pO2.

Prior to putting my head under, I would flush with Dil so I didn't enter the water with a high pO2 in my loop that I can't burn off fast enough, thus spiking my pO2 on decent. To illustrate this, if I started with a true .5 or higher, an immediate decent to depth will easily spike the pO2.

Also, in getting ready to do CCR Trimix, I've read this step is especially import so that the gas mix is correct in your loop, and not some weird mix of air + dil, which could make your N2 higher then your Dil.

At any rate, the Green Slow Flash is "normal" on entry, but more importantly, it is the ONLY warning of a low pO2 - Nothing secondary after that.

In my case, I am usually very diligent about watching my pO2, and my HUD was doing exactly what it should have. Had I sat on the surface resting, my pO2 would probably have climbed slowly. As it was, I was swimming quickly, which caused the high consumption (this was where I made the mistake - I didn't account for needing to check my pO2 even more often if I was on the loop at all!).

HUDs are great tools, but to paraphrase Dave Sutton who recently said "given all the right tools, the diver can still kill themselves" - Vigilance is the only way.