The Cabin Air Filter / Pollen Filter, cleans the air that comes into the interior of the car through the heating, ventilation and air-conditioning system. It catches dust, pollen and other airborne material that can make riding in a car unpleasant, particularly if you have allergies or other respiratory problems. The filters can also catch rodent droppings, leaves and other unwanted debris. By keeping the pollen filter clean you can help improve the performance of your ventilation or air conditioning system.