Filtra-Pak RP HEPA rigid pocket filters are a modern alternative to the traditional filters with equal efficiency levels. They are fitted with a fiber glass filtering medium, water-proof and fire resistant. It is closely pleated and separated with continuous thermal-plastic spacers. The packs obtained are positioned in a Vshaped pattern in a polystyrene, tight holding frame. The filters have a constant and tested filtering efficiency, they are not as deep as the bag filters, have a high dust holding capacity and robust construction. The pressure drops are limited and limit the energy consumption of the fans. At the end of their operating life, they need to be replaced