Not meaning to be argumentative but Im not sure of your comparing apples with apples in your eg above

Compare 2 cells with instant cell verification to 3 cells that you dil flush when they show up that there is any variance...

Andy: Well I think the instant DIL validation is so important I actually do it many times during a dive even though all cells reads the same. I have killed 3 cells on same dive in the same moment a few times, so I am very cautious and very alive. To compare: yes I agree the three cell system that you ACTUALLY DIL flush as many times as I validate is the same thing, but very unpractical due to the amount of wasted DIL and jumpy set point. Also consider that in order to get back to set point after a complete DIL flush in the shallows (assuming only one DIL) can easily create high Po2 spikes if you dont spend long time to build the set point back gradually. Coming up you might anyway have high CNS load and some times one breath of very high Po2 can push over the cliff. It is very interesting to see what such spikes can actually be on a simple (fast) Po2 display and that they never pick up on a slow responding ECCR hand set or VR3. Oups. drifting a bit...

Instant cell verification is just a fast dil flush - something thats taught on every ccr course as something you do if you have cell variances in a 3 cell system.

Andy: Yup. If you have lots and lots of DIL and time to kill you can do the same with any Rebreather. The number of cells is always better in the higher numbers. I am just saying I think it's crazy to only DIL flush or use instant cell validation only when cells disagree. In a Pelagian course we teach to grab every moment. Need to clear your mask? Check your cells when you inhale. Descending a bit? Check your cells etc. etc.

I agree if your not dil flushing to verify when a 3 cell system gives a variance that this isnt as safe as 2 cells that your are verifyijng - but who wouldnt flush in that situation??? it is SOP. (or at least its supposed to be )

Andy: Maybe a poll on this? I think people are mostly trained to DIL flush when cells disagree. Thing is that DIL flushes tends to play havoc with set point controllers. With MCCR this is not an issue and since the instant cell vaildation is hands free (ADV triggered) it is just a half breath through the nose and inhale slowly. Doesnt really drop the set point too much and also an easy way to check respond time in between cells, (forget VR3 as it is too slow to begin with).

Anyone can do a dil flush on any unit - maybe not as fast as on your - but it can be done - and is done. It would be cool if ot could be done faster as you seem to have set up - a good idea,

Andy: Yes isn't it! See above for my thoughts on why divers acutally do not flush frequently enough. If you had been diving a one cell system for 8 years that had instant cell validation I think you would see why validating the cell is just as important to read what it says. After all what is the point in reading something you dont know is accurate? Hold it. I am not saying it is better to have only one cell! Or actually it might be for the sake of drilling in the routine

As for calculating ppo2 easily at deep depths -i pressume your joking re additional helium. N2 is only part of the dumbifying effect and personally after a fast descent even on heliox Im as thick as pig sh1t sub 150m and deep = helium and thats where Im working hard and is therefore (He and exersion being high trigger to tox) where Im most concerned about too high O2 so deep is where Id want to flush (if I was diving a 2 cell system) = lots of dil (ordinarily)

Andy: Yes a partial joke. You can not disagree that too cheap mixes gets you more narced. For sure fast descents+Co2 are huge factors. Still I tend to check the cells and do the math frequently. I may come crying back admitting I was wrong after a few challenging deeper dives. Lets see.

My bob had fast cell verification for just the reason yours does - but I had 3 cells and would only flush if there was a variance as Im as thick as pig sh1t and too busy trying to do the dive .

Andy: Hr, hrm. My Rebreather usually has three cells in it but they all get validated even when they all agree. The real question is why your new RAT does not have it if your BOB had it? Did you have any reason not to have it inthe RAT?

I guess thats one way to look at it:
whats safer (jn all aspects) : 2 cells with instant flush or 3 cells which if they show any variance can be instant flushed? Hmm I may have to mod the RAT to give fast verification.....

Andy: Seeeen! The safest is to have three or more cells as isolated as possible and then validate them frequently and not succumb to a false sense of security just because three cells read the same. At least we can agree that cells are shitty and should not be trusted.

I agree there is a lot to be said for flushing cells at depth at intervals - regardless of what number of cells one is using and having a fast way to do that is a neat advantage - do you think this could help clear water off cell faces - I recall years ago the 'puffer' was tried