HEPA or ULPA - which final-stage filter fits?
HEPA and ULPA filters are the final stage of every cleanroom air handling system and define the achievable air cleanliness. This guide explains classes H13 to U17 under EN 1822, MPPS testing and how to choose the right filter for your ISO cleanroom class.
View filters and cleanroom gearWhat sets HEPA apart from ULPA?
HEPA and ULPA filters are high-efficiency particulate filters classified under EN 1822. HEPA covers classes H13 and H14, ULPA covers classes U15 to U17. The only real difference is the collection efficiency: the higher the class, the more particles the filter retains.
An H13 filter captures at least 99.95 % of the most critical particles, an H14 filter 99.995 %. ULPA filters continue this: U15 reaches 99.9995 %, U16 hits 99.99995 % and U17 achieves 99.999995 %. Each class cuts penetration by roughly a factor of ten.
Which filter for which cleanroom class?
The final-stage filter is chosen by the required cleanroom class under ISO 14644‑1. The lower the permitted particle count per cubic metre, the higher the filter class must be.
- H13/H14: standard for pharma, medical devices, food and general cleanrooms.
- U15/U16: semiconductor fabrication, optics and demanding assembly.
- U17: the highest demands in microelectronics and nanotechnology.
- As a final stage always inside a laminar-flow module or the filter-fan unit directly above the cleanroom ceiling.
What matters when selecting?
Beyond the filter class, size, frame material, seal and air volume decide the right choice. The filter must match the housing, the face velocity and the cleaning strategy.
- Every final-stage filter is leak-tested on site (DOP/PAO scan) for integrity.
- Pre-filters (M5-F9) considerably extend the service life of the costly HEPA/ULPA filter.
- Replace the filter when the final pressure drop is reached, not on a fixed schedule.
Frequently asked questions
What does MPPS mean for HEPA and ULPA filters?
MPPS stands for Most Penetrating Particle Size, the particle size that is hardest to capture. It usually lies between 0.1 and 0.3 µm. The efficiency stated under EN 1822 refers precisely to this critical size.
Is an H14 filter enough for an ISO 5 cleanroom?
In many cases yes. H14 captures 99.995 % of MPPS particles and, combined with laminar flow, reaches ISO 5. Only at ISO 4 or stricter are ULPA filters of class U15 and above required.
Why is ULPA not always the better choice?
ULPA filters have a higher pressure drop, cost more and lower the air volume. Where H14 reliably meets the cleanroom class, ULPA only adds energy and investment cost without real extra benefit.
How often must a final-stage filter be replaced?
Replacement follows the recommended final pressure drop, not a fixed schedule. Good pre-filters extend service life. Regular leak testing documents the filter condition.
Looking for the right HEPA or ULPA filter?
We supply final-stage filters from class H13 to U17 to EN 1822, including matching filter-fan units and pre-filters - matched to your cleanroom class.
Standard-tested
All filters classified and tested to EN 1822.
Leak-tested
Final-stage filters verifiable by on-site DOP/PAO scan.
Precise fit
Filter class matched to your ISO cleanroom class.
Expert advice
Cleanroom specialists support your filter sizing.