You can extend the life of a carbon filter by taking it outside, removing the pre-filter, putting your centrifugal fan on the top so it blows thru the carbon, and let it go for an hour or so. When I do it, a gray/beige superfine dust forms on the outside of the grill. This is only a small portion of the dust that's coming out of it [though you can't really see it much]. I let it blow, wiping it with damp paper towels every few minutes till not much dust keeps forming. Caution: I almost got my turned-up shirt cuff sucked into the 6" Vortex fan. Could have been a disaster as powerful as those things are. Put wire or something over the intake of the fan. Good luck. -granger