Pre-filter standards are primarily based on their filtration efficiency and particulate matter retention capacity. According to international standards ISO 16890 and EN 779, pre-filters are typically classified into four grades, G1 to G4, with specific standards as follows:
G1 Grade: Filtration efficiency of 50%-65% (for particles larger than 5μm), mainly used for pre-filtration, retaining larger particles such as dust and pollen.
G2 Grade: Filtration efficiency of 65%-80%, suitable for primary filtration in general ventilation systems.
G3 Grade: Filtration efficiency of 80%-90%, effectively intercepting fine dust and fibers.
G4 Grade: Filtration efficiency of over 90%, approaching the level of medium-efficiency filters, commonly used in locations with high air quality requirements.
Technical Principle: Pre-filters mostly use metal mesh, synthetic fibers, or non-woven fabrics as filter media, capturing particulate matter through inertial impaction, interception, and diffusion. Its pressure loss is usually controlled at 30-50Pa to ensure the energy balance of the ventilation system.