Types and characteristics of air pre filters

Air pre filters can be divided into three categories based on their structural form: plate type, bag type, and folding type. The plate type pre filter is mainly designed in a flat plate shape, with the filter material folded into a corrugated shape and fixed in a metal or plastic frame. It has the characteristics of compact structure and easy installation, and is suitable for primary filtration in small air volume scenarios such as central air conditioning fresh air systems and large air compressors. Its filtration efficiency usually covers G3 to G4 levels, and can intercept particles larger than 5 μ m. The paper frame version is mostly disposable, while the aluminum frame or galvanized iron frame version supports filter material replacement, balancing economy and practicality.

The bag type pre filter forms multiple filtering units by making the filtering material into a bag shape and fixing it on the frame, significantly increasing the filtering area. Its core advantage lies in its high dust holding capacity, slow resistance growth, and bag like structure that makes dust settling more uniform, extending the single use cycle. This type of filter is commonly used in central air conditioning ventilation systems, clean room return air systems, and industrial air purification fields. It is particularly suitable as a pre filtration device for high-efficiency filters, reducing the load on back-end equipment by intercepting coarse particulate matter. According to the number and arrangement of filter bags, bag pre filters can be further divided into single bag, multi bag, and combination types to meet different air volume requirements.

The folding pre filter adopts synthetic fiber or glass fiber filter material, and achieves high-density filter layer construction in a limited space through folding technology. Its V-shaped or wavy fold design not only increases the filtration area per unit volume, but also reduces resistance by optimizing the airflow channel. This type of filter combines efficient filtration and low resistance characteristics, and is widely used in ventilation systems in industries such as electronic manufacturing, pharmaceuticals, and food processing, as well as intermediate filtration in central air conditioning. Some folding filters use metal mesh or stainless steel frames, which support repeated use after high-pressure water gun cleaning, further reducing long-term maintenance costs, especially suitable for industrial environments with high dust concentration or frequent replacement.