I was just thinking that KEW's filter looks kind of industrial. Somebody must have figured that into the fan size.
Yes. If those pollen filters work like the ones I know, they aren't just a passive filter. They have large metal plates that get a high voltage static charge, making airborne dust particles stick. To clean them, remove the whole plate assembly and hose them off outside. The plates themselves are parallel to the air flow and don't impede the flow much. I had an older version than what KEW showed. His probably work better.
I went through something sort of similar with an air handler that was blocked. In my old house, there was one bedroom that was cold in the winter and hot in the summer. Sure enough, it got the puniest air flow. I thought I'd have to do something like install a powered fan in the supply duct to that room. Glad I never tried that.
An HVAC guy said my furnace fan was powerful enough but it was probably not getting enough air intake through the return vents, causing it to lug. So he cut another return intake near the furnace in the basement. That alone did the trick.
When he did that work, it was also easy to see how dusty the main return duct had become. The house was built in 1962, and after some 25 years, a long horizontal return duct had built up a dust blanket over 1" thick. The HVAC guy gave me the name of a duct cleaning company that wouldn't destroy my duct work. They removed about 30 or 40 pounds of dust! That also made the air handler fan & duct system work much better.
Having a built-in dust removal system, like KEW showed, could make a big difference in the long run, by keeping the whole system cleaner.
Warning: There are a lot of fly-by-night duct cleaners who can do major damage to ducts especially the soft flexible ducts. So be careful if you consider doing this.
