Pre-Filters

Pre-filters serve as the first stage of multi-stage air filtration systems, classified under EN 779 from G1 to F7, corresponding to the ePM10 range of ISO 16890. Their primary function is to capture large particles of 5μm or larger — including construction dust, pollen, hair, and fiber debris — thereby reducing the dust load on downstream medium and high-efficiency filters, extending their service life and lowering overall system pressure drop.

Three main structural types are commonly used: Panel Type with cardboard or metal frames paired with non-woven or synthetic fiber media, suited for high-airflow, low-pressure-drop applications; Bag Type with multiple filter bags offering large dust-holding capacity and extended replacement cycles; Pleated Type using folded media to maximize filtration area while minimizing installation depth. Frame materials include cardboard, aluminum, galvanized steel, and stainless steel, selected based on environmental humidity, fire rating, and service life requirements.

Typical applications include fresh air intake for semiconductor fabs, AHU pre-filtration for display panel plants, first-stage filtration in cleanrooms, general ventilation in healthcare facilities, and HVAC systems in commercial and industrial buildings.

Industrial air filters in HVAC systems fall into two main categories by installation position: MAU (Make-Up Air Unit) filters handle incoming outdoor air with the highest contamination loads — bag or pleated types with high dust-holding capacity are recommended; AHU (Air Handling Unit) filters handle return and mixed air with lower loads but higher efficiency requirements. Efficiency cross-reference: EN 779 G3 roughly corresponds to ASHRAE 52.2 MERV 5–6 [verify], G4 to MERV 8, and F5 to MERV 9–10. Industrial environments should also verify UL 900 fire resistance certification [verify] to ensure filter media will not contribute to combustion in high-temperature or spark-prone settings.