If you really want to use it for O2 instead of Air or N2, I think that is a bit excessive. Unless you have that device laying around for a few years already and took it from some shelf.
Basically O2 and N2 have almost the same conversion factor. You can easily adjust for that in software if you really are concerned about it.
Rolf Kalbermatter
My Blog 
DEMO, Electronic and Mechanical Support department, room 36.LB00.390