The rigid bag filters are constructed by glass fibers pleated within a plastic or metallic galvanized frame. They include the majority of the characteristics of the simple bag filters and is added to them their ability to be used in extreme air conditioning and ventilation conditions. They can be used mostly in industrial applications but also in generally large buildings where high air flow rate is required (hospitals, hotels, sports centers, etc.). They can separate from the air smoke and small particles at pollen size.