Pleated Filters

(Fractional Efficiency of Several Air Cleaners Over the 0.3 -- 10 µm Diameter Size Range)

One of the most effective ways to increase the particle collection efficiency of mechanical filters is to increase the filter media density using small denier fibers. This causes smaller media penetrations and increases the screening or straining mesh size. However, any increase in filter density significantly increases resistance to airflow, causing decreased airflow through the filter. The most effective approach to overcoming this problem is to extend the surface area by pleating the filter medium. This lowers the airflow velocity through the filter and decreases overall resistance to airflow such that pressure drop is reduced. Additionally, pleating of filter media increases the total area available for filtration and, thus, extends the useful life of the filter. The efficiency of extended-surface (pleated) media filters is much higher than for other dry-type filters. For example, Figure 5 demonstrates the efficiency of a pleated paper filter over the 0.3 - 10 micron diameter size-range compared to a typical flat furnace filter.