HEPA filters are highly effective in capturing 99,97% of fine particles that are 0.1 microns and smaller. According to NASA reports, this size of particles is considered to be the most penetrating particle size, therefore the most dangerous one.
The HEPA filter’s microscopic fibre maze consists of interlaced glass fibres that are twisted and turned. The small size particles are caught by the diffusion principle when floating through HEPA filters. By hitting and sticking to the sides of fibres, these particles are trapped and therefore not harmful anymore.