Classification of Filter Filtration Levels
The core of filter filtration level classification is based on international standards (such as ISO, EN) or industry specifications, with key dimensions including filtration precision (retained particle size) and filtration efficiency.
Common Filtration Level Classification Systems
1. Air Filters (per EN 779/ISO 16890)
Coarse filters (G1-G4): Retain particles ≥5μm with an efficiency of 10%-85%, used for fresh air pre-treatment.
Medium efficiency filters (F5-F9): Retain particles ≥1μm with an efficiency of 80%-95%, used for intermediate filtration in air conditioning systems.
High efficiency particulate air (HEPA) filters (H10-H14): Retain particles ≥0.3μm with an efficiency of 99.9%-99.995%, used in cleanrooms and medical settings.
Ultra-low penetration air (ULPA) filters (U15-U17): Retain particles ≥0.12μm with an efficiency of ≥99.9995%, used in semiconductor and biological laboratories.
2. Liquid Filters (per ISO 4406/ANSI)
Contamination class (e.g., ISO 4406 18/16/13): The numbers represent the count of particles ≥4μm, ≥6μm, and ≥14μm per milliliter of liquid.
Filtration precision (μm): Divided into coarse filtration (≥100μm), medium filtration (10-100μm), fine filtration (1-10μm), and ultra-fine filtration (≤1μm), suitable for hydraulic oil and water treatment scenarios.
3. Water Treatment Filters (by Filtration Precision)
Pre-filters (40-100μm): Retain large particles such as rust and sediment to protect household appliances.
Ultrafiltration (UF) (0.01-0.1μm): Retain bacteria and colloids while preserving minerals.
Nanofiltration (NF) (1-10nm): Retain organic matter and heavy metals, partially preserving small-molecule substances.
Reverse osmosis (RO) (0.1-1nm): Retain almost all impurities to produce pure water.
Core Judgment Criteria
Filter medium: Materials such as fibers, ceramics, and membranes determine the upper limit of filtration precision.
Application scenario: Air purification follows EN/ISO standards, hydraulic systems follow ISO 4406, and water treatment follows pore size specifications.
Efficiency index: Air filters refer to "count efficiency," while liquid filters refer to "retention efficiency."
