I have a pharma locations with some 100% OA AHU's up on the roof. The big complaint is insects and particles getting into the air stream. We use quality pleated filters and vacuum out the unit every 3 months.
The problem is there is nothing on the outdoor air hood. I was thinking about some sort of screen on the hood. Kinda like the cottonwood screens that I have seen on some condenser coils.
What you think?