Bag filters are used for the clarification/filtration of fluids that have a relatively small loading or particles to be removed. The particles suspension passes through and the particles settle in the bag. Filtration occurs from inside to outside with a delivery speed of about 100 m3/m2 h. Therefore bag filters are normally used with a supporting vessel. In situations where no support is used, the pressure drop across the filter needs to be lower. In situation where bag filters are used, industry standards normally define the size of the bag house. The supporting vessel provides mechanical support for filters with high throughput rates and prevents the filter material from elongating. Bag filters are normally made from needle punched nonwovens and act as depth filters. The pore volume varies between 70-90%. The filter bags are normally stitched at the edges. Bypass filtration can be avoided by welding the seams, however, this is only possible if the material used is thermoplastic e.g. polypropylene or polyester.