Filtrete 12"x12"x1" Red Micro Allergen Defense Pleated Furnace Air Filter. This filter is 90% effective at capturing large allergens like mold spores and pet dander, and it is electrostatically charged to capture microscopic allergens like dust, smoke, and smog. It also captures bacteria and particles that can carry viruses, meeting the guidelines of the American Lung Association Health House Program. With an MPR rating of 1000 and lasts up to 3 months, this filter helps reduce allergens in your air by turning your central heating and cooling system into a whole house air cleaner.