Ventilation fans fall into 6 categories, it is recommended that you determine the appropriate type of ventilation fans before purchasing. 1. Louver ventilating fan: directly installed on the hole of the wall, and the dirty air is discharged from indoor to the outside for fresh air. 2. Integration ceiling ventilating fan: integration ceiling is installed in the place where the ventilation fan is installed, there are pipes above the ceiling that are lined outside. 3. Pipe type ventilating fan: There is a ceiling where ventilation fans are installed, pipes above the ceiling that are lined outside. 4. Ceiling fan: There is a ceiling where ventilation fans are installed and the ceiling upper part has a direct row to external space outlet. 5. Shop-window mounted ventilating fan: Installed on glass doors and windows in living rooms, shopping malls, hotels, offices, and antanainment ventiac 6. Duct fan: Installed on the booster fan on the ceiling, applicable to house, office, shopping mall, hotel, hall and other place.