BERLÜF air handling units are equipped with high quality EU5 filters with an extremely large filtration surface. These filters are made of a synthetic fibre whose density is at an extremely high level; such a material structure results in a very high effectiveness in intercepting all the types of impurities. They create a large barrier against saprophytes which are harmful to allergy sufferers. Filters. The air handling unit is equipped with two EU5 class filters in a standard version. Owing to a simple installation system, their replacement does not require any tools. A pleated structure of filters enlarges the operating area of the filter, what contributes greatly to the total efficiency of the entire appliance. In order to guarantee the maximum efficiency of the appliance, you must use the original filters.