This is the completed filter, hung from the loft in the garage. It's high enough that I can walk under it and the minivan can still be parked in the garage, but not by a lot.

The filter unit is comprised of three pleated furnace filters and a squirrel cage blower that I got off eBay. There are two filters at the intake side and one filter at the outlet. This image shows the sliding bottom of the box pushed back and the outlet filter has dropped out. There are frames built into the inside of the box to hold the filters in place. The filters are 14 x 20, to give some idea of scale.

This is a view of the filter unit from underneath. The outlet filter is still out and you can see the blower and the inner-most intake filters. The blower is a 1/2 horsepower 4-speed job that I *think* used to be a furnace blower. I have it set to use the 2nd of 4 speeds. The blower is screwed to a mounting plate with a hole sized for the outlet. There are also a couple bolts supporting the blower from above cuz it's kinda heavy.

Now the bottom of the unit has been slid to the front and the two inlet filters have been removed so you can see my fine handwork wiring the switch and the back of the blower.

This is how the filters fit in the frames. This is the inlet end. The inner-most filter is in place and I'm ready to put the outer intake filter into its frame.

The same as described above, slightly different angle.

The other side of the reassembled filter unit. You can see the switch and the oversized switch plate that I put on it. Someday I'll buy a new switch plate but this is what I had laying around.

The bottom sits in a groove and is waxed so that it slides easily.

The outlet is strong enough to blow around a tshirt/rag hung about 8 inches from the outlet. The first time I fired it up it cleared the dust form the garage in just a few minutes.