Quote:
| Originally Posted by Decodiver ...
This is correct if you have ramped up your setpoint to 1.6, but is not symptomatic of O2 RBs per se.
If you use the unit as an O2 RB, after say a complete electronics failure, where you are flying by the seat of your lungs and running minimum loop volume and manually adding O2, then the drop will be as a result of O2 metabolisation.... |
I disagree. Taking the example of an O2 rebreather diver, where there is no inert loading (above atmospheric air) on the diver, the loop is flushed to contain pure O2, 100%, at 6m the PPO2 will be 1.6bar, whatever the loop volume. As the diver metabolises some of the O2 in the loop, the volume of O2 reduces, but it will still contain 100% O2, only less of it, so the PPO2 will still be 1.6bar so long as there is gas in the loop, no matter how much he metabolises... If we add in the element of a diver who's got an inert loading from doing a proper dive, his body will be offgassing the inert loading into the loop as he ascends, and will continue to offgas these inerts into the loop at the 6m stop, so the loop now starts to contain more inerts (plus less O2, from metabolism, but as illustrated previously this alone will not effect the PPO2 of a 100% O2 loop) and the addition of the inerts mean the %ages of the gasses change, effecting the PP of the gasses.
It's a moot point, but the metabolism of O2 in a loop will only affect the PPO2 if there were either inerts already in the loop (eg a poor O2 flush) or if the body is putting inerts into the loop (offgassing)
Not starting a fight - I'm a relative RB newbie - but I think I've got a good point, that can take a while to get the head around...