Schematic overview of the observational categories for ONC disks. Type I, the IF (Pa α emitting layer, in blue) is close to the disk’s surface and almost merged with the DF (H₂ emitting layer, in yellow). Type II, the IF is placed further away from the disk’s surface and DF. In these two first categories, the disk is in the H ii region and embedded in a photoevaporative wind (PAH emitting area) surrounded by a bright IF. Type III, the disk does not have any associated IF, but still has a DF. This corresponds to the case where the disk is FUV irradiated only, beyond the Strömgren’s sphere produced by the Trapezium.