O2 Flow Replacement Filter / True HEPA + Carbon Filter - 4 Stage HEPA H-13 Carbon Filtration

O2 Flow Replacement Filter / True HEPA + Carbon Filter - 4 Stage HEPA H-13 Carbon Filtration. Replacement filter for the O2 Flow Electric Face Mask. 4-Layer Super-Strong Composite Filter for Air Purification - HEPA combined filter four-stage filter system (HEPA filter, activated carbon, sterilization membrane, medical non-woven fabric), which efficiently removes fine particles in the air with a diameter less than or equal to 2.5 microns (equivalent to 1/24 of human hair) Particulate matter, such as viruses, bacteria, exhaust gas, formaldehyde, pollen, dust, allergens and other harmful substances, the purification efficiency is up to 98.8%, which really plays a defensive role in blocking harmful substances from entering the human respiratory tract and damaging the respiratory tract.