HEPA (High efficiency particulate air Filter), means the filter efficiency reaches 99.97% against 0.3um particle.
Compound HEPA filter is made of compound layer of primary material on the surface of HEPA filter, which can pre-filter large particles to protect the back-end HEPA filter on one hand, and on the other hand, it can also process the primary effect material and add other functions such as antibacterial, antiviral, and mite removal.