The 138 head, I assume the 139 is the same, has an opening for fan cooling directly above the lamp location. There are elongated openings that are baffles for exhaust air dissipation on each side of that opening. It may be that your opening is blocked off with a plate. Most of them are. Two small fasteners should open it up for you.Originally Posted by dogzbum
The fan that Durst calls out has a CFM rating of 70 CFM and the fan is downflow in it's operation. I came up with an alternative fan that moves over 100 CFM with the higher wattage lamp that I have. The fittings for the opening, to allow the fan to connect can be made up from PVC fittings available at Lowes. I have not melted anything down on the PVC with prolonged usage with the fan.
I sort of figured that it was foolish to reinvent the wheel on the air flow design. So I utilized what Durst designed. Good luck.