I deal with air cleaners on an everyday basis in HVAC.
From an air circulation standpoint the best location of the filter is in the center of the room, From an air cleaning standpoint the best location is near the source. The reason you will see so many mounted hanging from ceilings ect, is to make them accessible and keep them out of the way. Physical location will normally be decided based on whats practical for a given shop.
Thanks for the location information. Is there more detailed information somewhere?
How much clearance should I have on the intake side? I'm using a box fan with stacked filters. If I could mount it close to the ceiling and pushing air downward, I could create an efficient circular motion, down in the middle and up on the sides. Does this seem reasonable?
Types and methods of filtering are going to differ considerably based on where your wood working shop is located.
Mine is a dedicated shop, 16'x20' with 8' ceiling. It is insulated with 4" of Fiberglas vapour barrier and R40 in the attic. I have no icicles.
In a stand alone shop I would use a dust collector as the air filter. If you feel you need to reduce the dust levels apart from when you are actually making the dust with a tool, simply turn on your collector and open your ports, it will probably move more air and do a better job of filtering than a stand alone filter.
I've broken the dust issue into two parts: dust collection and air filtering. I'm working dust collection to MERV 8 and air filtering to MERV 8 and 1900MPS. I was using a 1 micron non-rated filter before and was having respiratory problems. I'm not going for minimalist now. If this doesn't work, I'll have to wear a fine particle gas mask.
Ok, what is optimal air movement? A shop vac moves from 135CFM to 185CFM. BusyBee's 5HP 220V dust collector moves 4820 CFM. My box fan moves 2100 CFM. BusyBee makes a big deal out of the noise being 90dB but nothing more than "1-Micron top bags" for filtering. No rating.
My shop is 16x20x8=2560 cubic feet. My fan will move all of that air in slightly over 1 minute given good air circulation. Theoretically, I can filter all of that air through my 1900 MPS filter in 1 minute 12 seconds.
If your shop is in your home the needs are probably quite a bit different. Room constraints can keep you from installing a central dust collection system. I would do a combination of things in that situation. First, still always try to collect the dust at its source, even if only using a shop vac. 2nd, stand alone dust collector with a mirv rating of at least 11. 3rd High efficiency air cleaner on the central heating or cooling system in the home.
Hope this helps.
Ok, can we put together a series of scenarios:
1. stand alone workshop: dust collection and air filter. Location of the air filter should be in the middle of the room or closest to the source of the dust.
2. in-home workshop: try to collect dust at the source and put in a high efficiency air cleaner. What rating should the air cleaner have?
Is there any other scenario that should be addressed?