1. Filtration Level Classification for Mainstream Media
Filters for different media have entirely distinct grading logics and representative standards. Below are the three most common categories:
(1) Air Filters: Focus on "Filtration Particle Size" and "Filtration Efficiency"
Widely used in cleanrooms, HVAC systems, and automobiles, they mainly adhere to the ISO 16890 standard (replacing the former EN 779) and HEPA/ULPA classification.
Primary Filters (G1-G4): Filter dust, hair, and other particles larger than 5μm. Used for initial filtration of fresh air in HVAC systems to protect downstream filters.
Medium Efficiency Filters (F5-F9): Filter pollen, fine dust, and other particles between 1-5μm. Installed in the middle section of HVAC systems to reduce the load on end-stage filters.
High Efficiency Particulate Air (HEPA) Filters: Filter particles larger than 0.3μm with an efficiency of ≥99.97% (Classes H13-H14). Applied in cleanrooms and medical equipment.
Ultra-Low Penetration Air (ULPA) Filters: Filter particles larger than 0.12μm with an efficiency of ≥99.999% (Classes U15-U17). Used in semiconductor manufacturing and biological laboratories.
(2) Water Filters: Focus on "Filtration Precision" and "Contaminant Type"
Covering scenarios such as drinking water treatment, industrial water use, and sewage treatment, their levels are mostly classified by "the minimum particle size they can filter" or "filtered substances".
Coarse Filtration (1-100μm): Filters sediment, rust, and large particulate impurities. Common in pre-filters for tap water and inlet filtration of industrial water pumps.
Fine Filtration (0.1-1μm): Filters tiny particles, colloids, and some bacteria. Used in water purifiers (ultrafiltration membranes) and industrial circulating water filtration.
Ultra-Fine Filtration (0.001-0.1μm): Filters viruses and macromolecular organics. Typically found in RO (Reverse Osmosis) water purifiers (for drinking water purification) and ultrapure water preparation in the electronics industry.
Specialized Filtration: E.g., activated carbon filtration (removes odors and residual chlorine) and ion exchange resin filtration (removes heavy metals and softens water). Classified by function rather than particle size.
(3) Oil Filters: Focus on "Filtration Impurity Particle Size" and "Industry Standards"
Mainly used in hydraulic systems and engine lubrication systems, they follow the ISO 4406 contamination level standard (expressing the number of impurities with codes).
Coarse Filters (10-25μm): Filter large particulate impurities in oil tanks and pipelines to protect key components like oil pumps. Common at the oil suction port of hydraulic systems.
Fine Filters (3-10μm): Filter tiny impurities in hydraulic oil and lubricating oil to control oil cleanliness. Used in system pressure pipelines or return pipelines.
Ultra-Fine Filters (≤3μm): Applied in scenarios with extremely high oil cleanliness requirements, such as precision hydraulic valves and aero-engine lubrication systems.
2. Core Indicators for Level Classification
Regardless of the filter type, level classification revolves around the following two key indicators. Understanding them allows for quick assessment of filter performance:
Filtration Precision: Refers to the minimum particle diameter that a filter can effectively trap, measured in micrometers (μm). A smaller value indicates higher precision.
Filtration Efficiency: Refers to the percentage of particles of a specific size intercepted by the filter. For example, HEPA filters have an efficiency of ≥99.97% for 0.3μm particles.
