FILTR Replacement HEPA FilterThe third filtration stage is the HEPA filter. Air is forced through the HEPA filter before returning to the environment. This filter is rated at MERV 17, representing a 99. 98% efficiency at removing particles as small as 0. 3 microns from the environment. This filter is capable of capturing carbon dust, viruses, bacteria, and smoke particles, providing an exceptionally clean output from the Revolution. It is recommended that the HEPA filter be