Redundancy question

[john j]

This is great, some nice calm debate and discussion. I hope we can keep this going.

This is a good question and I've thought a lot about it. I haven't done the analysis for OC deco but I have for CCR bailout/diluent choices. I ran a bunch of dive plans in the 150-450ft range for various bottom times in the 15-30 minute range, then plotted the total deco times as a function of what gas I would use for the second bailout/diluent gas. I plotted FO2 for the second bailout/diluent gas on the X axis and total deco time on the Y axis. It turns out to be a "u" shaped curve where both high FO2's and low FO2's for the second bailout/diluent gas cause increased deco times. The first bailout gas of course is the bottom mix so you stay on that until you reach the mod for the second bailout gas and then you switch. If you use an oxygen rich gas for second bailout, the MOD is shallow so you have to stay on the helium mix longer, so deco time increases. If you use an oxygen lean gas like air for the second bailout gas, the total deco time begins to increase again becasue the N2 gradient is less during your deco. According to the data, the lowest point of the curve was around EAN 34 or so, but when compared to air, it only gave a few minutes of reduced deco even for a long deep dive. Since air is easily available and cheap, plus you can breathe it deeper than any of the nitrox mixes I concluded that overall, air was the best compromise for the second bailout/diluent gas. I don't know how this would work out for a fully OC dive. It seems strange and I didn't believe it at first either so I checked the data again and it is correct. Again, it is a compromise so if you oly look at certain aspects of it you could easily argue against it. I am looking at the big picture here.