Printing with ABS is prone to warping due to non homogeneous temperatures of the layers. I noticed that my ABS prints always warped on the left side of the heat bed where the extruder fan is installed (I have a Prusa i3 MK3). I assumed that the extruder fan was creating an airflow with consequent thermal gradient on the ABS layers and then warping. Based on my assumption, I created this air duct to move the inlet flow far from the heat bed. I tested it and it seems to work!! Maybe this is a simpler solution to warping rather than build an housing.