There are many misconceptions about HEPA technology. Most people think that HEPA filters work like a net. If a particle is smaller than the holes in the net, it gets through. However,  HEPA filters don’t work like nets. Particles less than 0.1 microns in size, and other nanoparticles, get captured by a scientific process in the HEPA filter called diffusion. Diffusion is extremely effective in trapping ultrafine (less than 0.01 microns) particulate matter. According to NASA, HEPA filters capture “virtually 100% of particulates.”