This is a fan shroud designed for the 30mm stock fan on the Printrbot Play. I knocked this one together after noticing that a similar fan shroud for the Printrbot Play by Andy Leer was no longer available on Thingiverse.
This is based on a printed version of Andy Leer's fan shroud, and the dimensions and general design are close to the 3D printed version I had. Oddly enough, I deleted the gcode and stl after I printed a few copies of it, so I ended up rebuilding it in Fusion 360.
Update 20151124: Added a version with an angled vent, not blowing directly at the nozzle.