Ventury tube filter is main functions as an inductor of second airflow. When the filter bag removes dust and high-speed airflow passess through Venturi, it can induce a seond airflow that is 5~8 times the blowing compressed air into the filter bag, which is sharply expanded in a moment. Because of the reverse action of airflow, dust deposited on the filter bag will drop off. Venturi tube improves the pulse blowing strength and effect greatly. Consumption of compressed air is lowered and energy is saved.