I get this material in the 16" width and use it as a pre-filter upstream of the standard pleated filter on the 16"X25" return air intake on my house HVAC system. It was time to change filters, so a question about "washing" this material prompted me to do a little experiment. No, I didn't wash the material. I took it out and vacuumed it, using the "claw nozzle" on my shop vac. I took pictures, before, during and after--maybe I can attach the pictures after I post this. I will, if possible. But just a couple of passes with the vacuum easily lifted out "most" of the accumulated "gray dust" from the material. No, it did not return to "pure black"--but maybe 75% of "pure black"--maybe more. My concern was that vacuuming (or washing) would lift out carbon particles and compromise this material's ability to absorb odor. There is no way for me to judge about the odor, but that's not my main objective using it anyway. Just holding the vacuumed piece up to the light next to a new piece, I couldn't tell any difference in opacity, though--they looked the same. So I taped the vacuumed piece onto a NEW pleated filter and will give it a second cycle, serving as pre-filter. I suspect it will do THAT job through at least another cycle. BUT, if I were trying to achieve a true "HEPA" result for medical reasons--I don't know--re-using after either washing or vacuuming might not be a good idea. It would take a more scientific analysis than mine to determine that.
