The dust laden gas enters through inlet nozzle and spreads all over the entire cross section of the bag filter.  The gas moves up & passes from outside of the bags into them and rising up; enters the clean air plenum through cleaning the top open end of the bags. During the passage of the gases through the fabric, the dust is retained on the outside surface of the bags.  As the filtration proceeds the thickness of the dust layer on the fabric surface increases resulting in increase in pressure drop through the fabric.  This necessitates the of the bags. Since the air flow is from outside to inside, the bags tend to collapse and are held by the wire cages, whose shape they take. The compressed air passing through the blow nozzle injects at very high velocity and pulse is of very short duration.  This produces a shock wave which is propagated down the bag length, causing the bag to expand and snap away from the cage, dislodging the dust cake which falls into the hopper. This unit is generally meant to operate with a pressure differential of 100-125 mm W.G.Cartridge Collector: Second type is called the “Cartridge Collector”.Construction and operation is similar to pulse jet bag filters, except the fact that cartridge filters are used instead of bags resulting in Compact design, Energy efficient, quick filter changes and ease of maintenance. Horizontal cartridges are secured by a quick-twist clamp on a frame inside the body of the collector. Further, easy access to filter cartridges is provided via side doors.  Cleaning of the filters is manual by blowing compressed air on the filter fabric to dislodge the dust.