Hello Logikman: I did my charcoal filters a week ago and unfortunately the old ones went out with the trash. They were quite heavy and dirty, with powdered charcoal present on the surface of the grids. The replacements, were different construction. Wavy folded with porous fiber covering but inside the same plastic containers. Suspect they are aftermarket, but did not ask Phil at Fastlane. Sorry I did not know about your project. I would assume that since the dust filters are first in line, that the only thing getting through to the charcoals are micron size and since they are activated charcoal, their primary effect is to adsorb (surface connect) gases, odors. They then get heavier as they go and eventually also plug up with any particulate matter that gets through the dust filters. If the dust filters are changed at appropriate intervals, the charcols should last longer, esp for people like me who do not use them too often. (Tulsa Oklahoma). I did note that since my old charcoals were full that they did inhibit the flow of air considerably when swithed on. Now the flow is much improved. That's about the sum of my knowledge. Regards, Harvey

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