Hepa type filters are those that look like true hepa filters but dont meet the same requirements. Minimum particle size i remember is about 02 microns. Hepa Wikipedia Hepa filters are incredibly effective at capturing nanoparticleseven smaller than the coronavirus. Hepa filter smallest particle . As defined by the institute of environmental sciences and technology iest rp cc0013 and mil std 282 method 10291 a hepa. That intuition is true for big particles. If youve ever bought an air purifier or vacuum you can probably add hepa to that list. Think about the long list of important terms buzzwords and acronyms in your life that you havent quite wrapped your brain around. Hepa filters are composed of a mat of randomly arranged fibres. What is a hepa filter. But this is final stage filtering. Basically hepa is a type of filter that can trap the smallest particles 03 micrometers um in diameter that other air filtr...