Bag filter is a dry dust filtering device. It is suitable for capturing small, dry, and non fibrous dust. The filter bag is made of textile filter cloth or non-woven felt, and uses the filtering effect of fiber fabric to filter the dusty gas. When the dusty gas enters the bag filter, the large and heavy particles of dust settle down due to gravity and fall into the ash hopper. When the gas containing fine and small dust passes through the filter material, the dust is blocked and the gas is purified.