Ryco n99 microshield cabin air filters incorporate medical grade media technology to filter out virus. Bacteria from the air flow. The microshield media is comprised of three layers. 1. Pre-filter with anti viral agent. 2. Activated carbon (odour barrier) & 3. Electrostatically charged layer for optimum particle filtration. Anti-viral. Anti-bacterial agents within the media eliminate virus. Bacterial from the air flow. Stops them growing in the filter once trapped. Acts as an odour barrier protecting vehicle occupants from harmful exhaust gases. Noxious odoursfilters particles that are. 3 micron or greater in size that can penetrate deeper into the respiratory system. That's small when compared to the human hair which is approx. 9 micron. Flame retardant media