1. Core principle: three-layer interception + Brownian motion
Inertial Impaction
Large particles (>1 µm) cannot follow the airflow due to inertia and directly hit the fiber mesh and are "stuck".
Interception
0.3-1 µm particles move with the streamline and are attached if they are close to the fiber.
Diffusion
Viruses and VOCs <0.1 µm drift irregularly due to Brownian motion and are eventually captured by the fiber.
Electrostatic Attraction
Modern composite fibers carry static electricity and can additionally absorb charged particles, increasing efficiency by another 5-10%.
2. Efficiency level: H13 vs H14, don't just shout "HEPA"
In 2025, EU EN 1822-1:2009 will still be the most commonly cited test standard:
| Grade | 0.3 µm Efficienc | Application Examples |
| H13 | 99.95% | Household air purifier, car filter |
| H14 | 100.00% | Hospital operating room, semiconductor clean room |
3. Structure: Pleats + Partition = Maximum Dust Holding Capacity
HEPA is not a "net", but a glass fiber or PP blend with a diameter of 0.5-2 µm, which is pleated hundreds of times and separated by hot melt adhesive to form a "deep bed" structure 3-5 cm thick. The more pleats, the larger the surface area and the longer the life, but the pressure loss will also increase. High-end models will add a MERV-8 pre-filter to block large particles first and extend the HEPA replacement cycle.
4. Maintenance: differential pressure gauge + regular replacement
• Home use: Replace every 6-12 months, or replace when the pressure difference is >150 Pa.
• Industrial: Measure the pressure difference every month, and replace it if it is >2 times the initial resistance.
• Washable? Only a few PTFE-coated HEPAs can be washed lightly, and the glass fiber will be destroyed when it comes into contact with water. Please follow the instructions.
5. Popular application scenarios in 2025
• Smart home: Sweepers, air conditioners, and humidifiers are all equipped with H13 as standard.
• New energy vehicles: H14 cabin air conditioning filter element has become a selling point for high-end models.
• Medical: Mobile PCR cabin uses U15 ULPA, with a virus retention rate of 99.9995% below 0.12 µm
Post time: Jul-22-2025