The ventilation system of the D'ni cavern was composed by massive shafts and fans that supplied the D'ni with fresh air from the Surface.

Work of the ventilation system was made during 84 DE and 114 DE. A small group of D'ni fled to the surface at this time and was believed mixed themselves with humans. This contact however was undocumented, and the first 'official' contact with the surface would wait for millennia later.

The ventilation system unfortunately played a major role in the fall of D'ni. Veovis and A'gaeris released their lethal plague cloud through the vents of the Cavern, whence it spread through all the City.