I find it difficult to believe that a furnace filter mounted on a box would filter down to 1 micron as the Delta and Jet air cleaners do with their electrostatic and fine interior sock filters. After reviewing many air cleaning machines with fellow wood workers, we did determine that Delta, Jet, and EDS do an excellent job.
I finally purchased a Jet 1000B unit because it is three speed, has automatic shutoff after either 2, 4, or 8 hours so can can sand all day, run the unit after you go upstairs to bed. I liked the fact that he had a separate controller that you could use like a vcr controller without having to reach up to this ceiling hung unit.
Now, I can begin to stain or varnish, or whatever other finish I might want on my furniture and wood working projects without the finish being contaminated with dust in the air.
Hope this helps. Oh yes, many of the guys built their own boxes with filters mounted and they ALL went with the air cleaners and are happy they did so.