Rawnoc, it takes a lot of extra energy to free oxygen into it's gaseous form, breaking the bonds of molecules, and that must come from somewhere.....
this is basic chemistry and thermodynamics.....when you burn something, it combines with oxygen, releasing energy.....it will take at least the same amount to free it in the reverse reaction (think of this as "un-burning, if you like, to get an idea of the energy needed).....
and this is just on paper, theory...accomplishing it for real with decent efficiency and economy is no small feat.....I doubt P2O also does this too with energy to spare....
PS: I don't know where the idea came from that P2O will produce gaseous oxygen and vent it, never saw the Co state that......
Hopefully there won't be too much oxygen though, I agree, pouring into the air outside. Just think what could happen if somebody breathes some of that stuff in? The last time I saw a dude take in too much oxygen he was at the bottom of a lake with scuba gear on. Scary stuff.