Lindhaus S-Class Upright HEPA Filter Fits the Healthcare-Pro Hepa 12" & 14" models. This optional Certified S-Class HEPA Exhaust Filter can be used instead of the standard Filtrete exhaust filter for even cleaner air. This filter is highly recommended for those who have dust related allergies or asthma. It should be replaced every 12 months with typical household use. The completely sealed systems in Lindhaus HEPA uprights, when equipped with Certified S-Class HEPA Filters, will retain 99.97% of pollens, household dust, dust mite droppings and other allergens as small as 0.3 ?m in size.