I don't own one, but this kind is not HEPA, coz there's no HEPA filter inside. They work by electrostatic attraction. I ever own a small electrostatic purifier, can see a layer of very fine dust (like smoke deposits) on the plates after running for a while. I don't doubt the effectiveness, just that you need to keep the electrostatic filter clean once in a while else no more new dust can stick to it. The PM 5.0 is talking about the prefilter not the electrostatic filter, which can remove stuff much finer than that.