Bag In Bag Out Filter, commonly known as BIBO, also referred to as the duct-type air return filter device. Since the filter has retained highly active or highly toxic harmful aerosols during the working process, it is necessary to ensure that the filter does not have any contact with the external environment during the replacement process. It can effectively prevent the spread of harmful aerosols and avoid biological hazards to personnel and the environment. It is a filter device used in a specific biological environment to remove harmful biological aerosols in the air return process. At present, it is mainly used in high-level biosafety laboratories, hospital isolation rooms, pharmaceutical equipment, microelectronics environments, food processing areas, industrial processing exhaust systems, chemical processing equipment, air supply or exhaust air processing systems for animal disease research laboratories.