I must respectfully disagree. Although being very economical, panty hose are very poor filters. everything smaller than the largest opening in the mesh will be sucked through and blown out into the house. I think you could avoid many potential problems by using REAL hepa filters. Industial filter pads are cheaper in bulk. check the specs and government ratings . Don't go too small with filter pores, or your vac moter will suffer. A prefilter and maybe panyhose (hey) will help the filter's longevity. Totally worth it. Trust me, I'm Particle Man