This is a working air ventilation for the Rift CV1.
You need a 35mm Radial Notebook-Fan 5V
A Tube. (event. insulation from a thicker USB-cable)
A Power Source( i use a 18650 Akku)
double sided Tape
and you have to make small slots in your Facemask
it blows slightly, but thats enough to prevent fogging, and does not
draft your Eyes. (i use a lensholder also, maybe this prevent also draft)
only 1 Infrared LED becomes concealed, this should have no effect tracking.