Spray Booth Dilemma

Along those lines, I was thinking about this a lot at work last night. I began questioning whether the down-draft with a filter on top of the booth would not be a better solution. It would draw a mix of dirty and clean air while open (spraying a model), but almost all clean air when closed (drying). I believe the risk of drawing contaminates onto the model, while the booth is open, might be mitigated by a couple things: 1) the booth I have is fairly deep, which would reduce the amount of un-filtered air drawn; 2) the air displacement around the subject may act as a sort of barrier against dust particles and the like, which would be drawn into the exhaust. Also, an advantage of the down-draft is almost twice the efficiency of a cross-draft. The biggest advantage of the cross-draft, that I'm seeing so far, is the work height. I'm going to keep giving this thought. I hope to get this thing built and operational this weekend

Actually, I have put a lot of thought into this.  The best solution for the model, though not the shop, would be a laminar flow bench like they use in cleanrooms.  The fan sucks air from the room through the filter, then onto the bench, with a large aerodynamically shaped outlet.  So the air flowing across the bench is filtered, but with a spray booth that means the overspray ends up in the shop :-(  But it would make a great paint job on the model, though!

Thanks Don. Your reply helped me confirm some conclusions I was coming to. I've only found one thing about hobby booth design that covers draft direction, and it jumps from 1:1 design right into hobby booths without explaining the difference in a way that I immediately understood. It appeared that the author was suggesting a down-draft would be ideal. In a sealed, 1:1 booth, it would be ideal - from an airflow/power perspective - but a sealed booth is free of contaminates, unlike an open-face hobby booth. I see how a down-draft would pull any airborne particles onto a typical model, while a cross-draft will pull them across and away from the subject. I'm going to go with the cross-draft design. Thanks again for the input

I believe a downdraft booth pulls more crud down on the model. I prefer the kind that draw towards the rear.