HEPA filter

The Philips hi-grade HEPA filter effectively filters out bacteria, ultrafine particles larger than 20 nanometers including some viruses. According to 2008 Microbiological Risk Assessment Report of the World Health Organization (WHO), the avian influenza, human influenza, Legionella and hepatitis viruses and the SARS coronavirus are larger than 0.02 microns (20 nanometers).