When I get a chance I will do a little research on that filter. Given the very low cost of the filter I doubt that it has 0.3 micron pores. Micron filters get their effectiveness by randomly overlapping layers of material that has a relative small porosity. 10 microns is typical of a good household filter. That being said, HEPA filters generally filter high 90% of of the particulates one order of magnitude smaller than the porosity. Marketing folks often spin their specifications using this factor and I suspect Electrolux is doing just that.