This inline filter unit is positioned alongside the main BOFA fume filtration system to increase the overall filter capacity and extend the life of the main filters. The DeepPleat DUO pre-filter incorporates a massive drop-out chamber within the filter, having a volume area of 15ltrs. Above the drop-out chamber but still, within the housing, there is a sealed 200mm deep pleat layer of F8 media giving a surface area in excess of 30 sq. metres.