The normal setting for fresh air make up is in the region of 15% or 85% re-circulated air.
That is to make up for small loses(mainly due to leakages in the ducting, door seals etc) and for personnel comfort, but this figure does vary due to the way in which the system is set up to handle the differential pressures required.
I have yet to find any standard relating to a ‘set figure’ required for fresh air make-up or re-circulation of a cubicle/room.
If by ‘abducted air’ you mean the air that is being returned to the AHU, the main reason we measure the return air is to verify the losses of the system. The more fresh air, the greater the losses, the harder a system is required to work to maintain the correct critical parameter.eg %RH, Temperature, air change rates, filter life, air velocities increase to overcome the air quantity losses.
Hope that this is of some help. Anyone else?