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Air filters are generally classified into three main grades based on their filtration efficiency and particle capture capability: primary-efficiency filters, medium-efficiency filters and high-efficiency filters. They are often used in series in a system to form a filtration barrier ranging from coarse to fine, so as to extend the overall service life and ensure the final filtration effect.
Definition & Functions
Positioned after primary-efficiency filters, medium-efficiency filters play a connecting role in the filtration system. They can effectively capture medium-sized particles (1–10μm in diameter) that cannot be trapped by primary-efficiency filters, such as most pollen, spores, bacteria and fine dust. By further reducing the load on subsequent high-efficiency filters, they are a key component to guarantee the service life of high-efficiency filters and the final air quality.
Efficiency Standards
According to the MERV standard, their rating usually falls between MERV 5–13.
According to the European EN779/ISO 16890 standards, they exhibit a certain filtration efficiency for fine particles.
Common Materials & Types
Materials
The filter media are mainly non-woven fabrics made of glass fiber and synthetic fibers (PP, PET).
Types
Bag type (medium-efficiency bag filters), panel type, combined type, etc. The bag type is widely used due to its larger filtration area and high dust holding capacity.
Main Application Scenarios
Intermediate filtration for central air conditioning systems in places with high air quality requirements, such as hospitals, schools, office buildings and shopping malls.
Primary clean areas in the food, pharmaceutical and electronics industries.
Intermediate filtration stage of clean rooms.
Features
Moderate filtration efficiency and air resistance.
High dust holding capacity.
Non-cleanable; requires regular replacement (usually every 6–12 months).
