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hepa (High Efficiency Particulate Air) filtration systems are key components in cleanrooms for removing airborne particles. HEPA filters have extremely high filtration efficiency and can remove more than 99.99% of particles as small as 0.3 microns.
How it works
hepa filters are made of layers of glass or synthetic fibers that are very fine in diameter, usually between 0.5 and 2.0 microns. When air passes through the filter, particles collide with the fibers and are captured.
The filtration efficiency of a HEPA filter depends on several factors:
Fiber diameter:
The finer the fiber diameter, the higher the filtration efficiency.
Fiber density:
The higher the fiber density, the higher the filtration efficiency.
Airflow velocity:
The lower the airflow velocity, the higher the filtration efficiency.
Filtration mechanisms
hepa filters remove particles primarily through the following four mechanisms:
Inertial collision:
Larger particles cannot follow the airflow around the fibers due to inertia and collide with the fibers.
Interception:
Smaller particles cannot pass through the gaps between fibers due to their size and are intercepted.
DiFFUsion:
Very small particles collide with fibers due to Brownian motion.
Electrostatic attraction:
Some HEPA filters are treated with an electric charge to remove particles using electrostatic attraction.
Filtration efficiency
The filtration efficiency of HEPA filters is usually expressed using penetration, which refers to the percentage of particles that pass through the filter without being captured. For 0.3 micron particles, the penetration of HEPA filters is usually less than 0.001%.
Application
HEPA filtration systems are widely used in places that require high air cleanliness, such as modular clean rooms, hospitals, pharmaceutical factories, and Electronic manufacturing plants. HEPA filters can effectively remove particles such as dust, pollen, bacteria, viruses, and smoke from the air.
Related standards and specifications
ISO 29463: High-efficiency Air Filters (HEPA filters) and ultra-low penetration air filters (ULPA filters)
EN 1822: High-efficiency air filters (HEPA filters)
GB/T 18230: High-efficiency air filters (HEPA filters)
