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What are HEPA filters?
HEPA filters, also known as absolute filters, are filters with an extremely high separation efficiency. These filters are capable of removing minuscule particles from the airflow. HEPA filters are used in hospitals and various industrial sectors where sterile air is a requirement. These include food processing companies and semiconductor manufacturers.
The essence of HEPA filters
The acronym HEPA stands for High Efficiency Particulate Air, indicating that these filters are particularly efficient in capturing microscopic particles. They are capable of trapping particles ranging from 0.1 to 0.2 microns and larger, including dust, pollen, mold spores, and even certain viruses. These filters can be used in various ways and are suitable for different applications. HEPA filters are especially used in environments where hygiene is crucial, such as hospitals and cleanrooms.
Operation of HEPA filters
The operation of HEPA filters is based on a combination of the mechanical and electrostatic properties of the filter media. The filter fibers, often made of glass fiber or synthetic materials, form a tight network. As air passes through the filter, particles are "captured" by the fibers. Small particles are captured through diffusion, while larger particles are mechanically blocked.
How are HEPA filters tested?
Absolute filters undergo various tests in accordance with the European EN1822 standard: 2019. After these tests, the filters receive a classification such as EPA, HEPA, or ULPA. Within these classifications, they are further subdivided with specific numbers such as E12, H13, or U16.
During the test with the test aerosol, measurements are taken. Given the variable performance of the filter at different measuring points on the filter surface, the minimum result is taken as a reference. The smallest particle that is allowed to pass through is known as MPPS. This stands for 'Most Penetrating Particle Size'. Smaller and larger particles than the MPPS are better captured than the MPPS.
What is the difference between EPA, HEPA, and ULPA filters?
EPA, HEPA, and ULPA filters all fall under the general term of absolute filters. However, there are significant differences. The main distinction lies in their efficiency in capturing MPPS. Absolute filters focus on the smallest particles, but the efficiency varies between 85% and 99.999995% for MPPS.
- EPA filters, which stands for 'Efficiency Particulate Air', have an efficiency of 85% to 99.5%.
- HEPA filters, which stands for 'High Efficiency Particulate Air', have an efficiency of 99.95% to 99.995%, allowing them to capture even more particles than EPA filters.
- ULPA filters, which stands for 'Ultra Low Particulate Air', go beyond HEPA filters with an efficiency of 99.99995% to 99.999995%.
| Filter class | Integral value Efficiency (%) | Penetration (%) | Local value Efficiency (%) | Penetration (%) |
| E10 | ≥85 | ≤15 | * | * |
| E11 | ≥95 | ≤5 | * | * |
| E12 | ≥99.5 | ≤0.5 | * | * |
| H13 | ≥99.95 | ≤0.05 | ≥99.75 | ≤0.25 |
| H14 | ≥99.995 | ≤0.005 | ≥99.975 | ≤0.025 |
| U15 | ≥99.9995 | ≤0.0005 | ≥99.9975 | ≤0.0025 |
| U16 | ≥99.99995 | ≤0.00005 | ≥99.99975 | ≤0.00025 |
| U17 | ≥99.999995 | ≤0.000005 | ≥99.9999 | ≤0.0001 |
Free advice on HEPA filters?
Do you need more information or free advice on HEPA filters? Feel free to contact me and I will be happy to assist you in selecting the right absolute filter.
