MERV 8. NaturalAire Standard furnace filter. Convenient to use and easy to replace. Ordinary furnace filters are designed to protect heating and cooling equipment from the insulating properties of relatively large airborne particles. Removes microscopic particles that can stain walls and furnishings as well as those that aggravate seasonal allergies. Up to 90 days effective against pollen, pet dander, dust mites, dust and lint, mold, bacteria, and virus carriers.