Bag coarse filter is mainly used to filter and remove ≥5μm dust particles in the air conditioning system. The ordinary flat filter is 592*592, provided with 3-12 parallel bags, bag depth generally ranging from 250~900mm. Ultrasound welding spacers between individual bags ensure an even airflow throughout the filter, which allows dust loading and even distribution. This results in long service life of the filter and reduces energy costs. The bag can be provided with a separation fence inside to effectively increase the filtration area.