CCR "Myths"

My issue was caused 100% by me. We were doing a night dive and playing with the flourescent lights & mask screens. It was day 1 of the trip, second dive after arriving at 2:30, and I was diving with steel 29's for both O2 & diluent I hadn't worked out my weighting with the unfamiliar setup yet and I was overweighted. Between the cool stuff we were looking at and the mask shield and the coral spawning, I was distracted. Totally my fault. Descended farther than I planned and before I knew it I was heading to 2.0.

Several valuable lessons learned and I lived to dive another day, needless to say I pulled the mask shield off and the next morning I got my weighting dialed in.
 
Captain Starfish said:
Now I get it, Ben.

If the breather is telling you 1.3 then all you know is that the breather has driven the loop to what it thinks is 1.3. Without a "calibration" flush of dil or O2 you really don't know for sure what's in there.

Still, reading the handsets is a good start and you'd be having a God-awful day if three cells agreed on the wrong value to lead you into a false sense of security.
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Yes, sort-of.

Also the "reading" tells you the display thinks the loop is 1.3 for the amount of time you where looking... fine if it was 1.3 last time and you have no reason to suspect it won't be 1.3 next time but what if it was 1.27 last time you looked? Did you do less in the last minute or two, did you descend, are you continuing to descend, did you inject Dil (what is the Dil PPO2 at this depth)- you should Know what the PPO2 will roughly be each time your look IMO.

If its higher or lower than expected and not moving in the right direction at the expected rate then these are issues.

Simply reading 1.3 tells you only a small part of the story.

I feel alot of divers see what they think should be there and don't think anything or it... why is it 1.3?


Don't forget that 3 perfect sensors could kill you if you analysed your gas wrong, calibrated poorly etc.
 
Great points Ben and all down to the "automation" we have built into our psyche. Small changes are hard to spot, and if we don't have a complete picture, our brain fills in the gaps of knowledge. The problem is that that small change that we missed may be vitally important in trying to determine why something is going wrong.

Regards
 
Ben Field said:
Know your PPO2 is abit of a Steady Green to me... if it doesn't change how do you know it isn't stuck?
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Is having a stuck readout been implicated in an actual accident?

Obviously every huge life threatening problem started out with a small change which grew. But at least on internet dives, I seems like the intellectual minutia are of bigger concern that the actual distribution of risk factors.
 
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