For coping with aerosol infection in indoor settings, continuous ventilation and high efficiency air filtration are recommended. For air filtration systems, the reduction efficiency of airborne viruses in an enclosed space is important. Air purifiers with the high efficiency particulate air (HEPA) filter has been generally accepted as the best system because of their highest performance in removing airborne particles. However, whether the HEPA filter is essential for airborne infection control or not is inconclusive because of the great loss of filtration volume per hour by its air resistance. The performance of air purifiers containing an HEPA filter or an efficient particulate air (EPA) filter, a slightly less efficient filter to the HEPA as per the European Standard EN1822, was compared in the 25 m3 and 130 m3 closed space with respect to removal of artificial airborne particles and the aerosol containing influenza A viruses. The latter showed a 15% and 10% higher reduction rates in particle counts and airborne virus titers, respectively, than the former, supporting our theoretical calculation that removal is not solely dependent on a high particulate removal efficiency of the filter, and thus, suggesting an advantage of EPA to HEPA in practical settings.