Quote: (Originally Posted by
Marc T)

Thanks for this interesting and very complete answer.
The initial idea was a more general self questionnemnt about the effect of diluent pollution when using a Rebreather versus on OC ( less diluent used - less pollutant in the loop and in the body)
It could be of course the contrary in case of O2 pollution with a progressive increase pollutant level inside the loop during the dive ( using industrial O2 grade is very common in France when personnal use

)
If you worry about CO in your rebreather then maybe you should consider a known CO source that cannot be removed. Your own body!
Have a look at this posting for more details:
http://www.rebreatherworld.com/rebre...html#post48795
Not that I think it is any issue for 'normal' Rebreather-dives.