| Re: CCR Trimix Simplified by Mel Clark question
My personal parameters (which may not be yours):
SCR is something that you perform when your handsets die and you want to extend your gas while having a good, working scrubber. If you are a long way back in a cave and want to give yourself a good margin for the already adequate gas quantity you are carrying (not in order to make the inadequate amount of gas barely get you out alive), you can extend that gas by going SCR, use OC for steep ascents to reduce the chances of hypoxia, and then go on the loop for an O2 flush at 20 feet. In such a situation, I'd do extra deco to make up for possible miscalculation from the SCR time and how this affected your deco obligation. Sure, you could have just gone OC for the entire exit, and there is nothing wrong with this per se. However, going SCR will make sure that any unexpected delays don't bring you down to a critical gas margin, which adds further stress to an already stressful situation.
Now, if you had both breakthrough and were running low on gas at the same time, SCR is something you can resort to because you don't have many other choices. Hopefully, by slowing your workload, your scrubber can still be effective enough to get you back alive. Howevever, SCR in this situation should be a last resort because you could black out and die from CO2 at any point. SCR is not something you do when you have plenty of gas and a dead scrubber.
If I were to have any kind of strange feeling during a dive, I would activate my BOV for a few sanity breaths and would stop all activity. (If necessary, I would then go OC until my breathing rate would back down.) If I had been working hard up to that point, I would suspect (assuming my PO2 were within range) a CO2 issue, and then I would go back on the loop, flush and test while remaining stopped and without work load. If I felt at all out of the ordinary again (and believe me, I would be with all radar in motion to detect this), I would go OC and I would stay off of the loop from that point on (unless my life depended on going SCR to try to extend my gas).
Always carry adequate bail out. The choice is easy and safe in such a case. |