I took inspiration from another fan duct and made this vent to suit the other ducts I have made for the Tevo Little Monster.
This vent goes front and back to ensure no air is being blow onto the heat bed or print from the heatbreak cooling fans. There is a gap between the grill to ensure a very low static pressure drop.
I strongly suggest you order some filter wool/mat (I use carbon mat for air-conditioners) and cut out a small circle to go into the intake side of this vent to prevent any dust build up in your heatsink and fan. It only takes a small amount of dust to significantly reduce the cooling for the heatsing and any dust on your fan makes it louder and ruins its lifespan. This lack of cooling on the heatsink is the number 1 reason for jams/clogs in hotends (E3D units are notorious for this due to the crappy fan and heat sink shroud design), if you are running all metal hotends (like everyone should) and you are getting jams you can almost be certain it is heat-creep causing the issue.
I also recommend you run your heatsink cooling fans as dual push-pull configuration, this will cut down on noise and drastically increase the cooling even with the restriction added from a filter.
PLA is fine to use if you don't have a heated chamber, otherwise use ABS or polycab.