Understanding HEPA Filter Classes

What "HEPA" actually means

HEPA is a performance class, not one universal test. EN 1822 defines HEPA and EPA grades (E10 through U17) by efficiency at the Most Penetrating Particle Size (MPPS) — the particle size a given media is least efficient at capturing. Other regional standards define HEPA slightly differently, so a filter's classification is only meaningful alongside the standard and test method used to establish it.

H13 vs H14, and where ULPA fits

H13 (minimum 99.95% efficiency at MPPS) and H14 (minimum 99.995%) are the two HEPA grades most commonly specified in cleanrooms, pharmaceutical HVAC, and other critical filtration. ULPA grades (U15–U17) sit above HEPA, reaching 99.999% and beyond, for the most particle-sensitive semiconductor and precision-manufacturing environments.

Nominal efficiency describes typical performance; absolute efficiency is the minimum guaranteed value, verified by individual scan or leak testing rather than a batch average — this distinction matters most for HEPA/ULPA grades, where a single leak point can defeat the filter's rated performance entirely.

Construction and installation implications

Deep pleat, mini pleat, and V-bank constructions all reach HEPA-grade efficiency but trade off differently on installation depth, weight, and pressure drop. Gasket integrity and frame sealing matter as much as the media itself — an otherwise correctly rated HEPA filter installed with a poor seal will not deliver its rated performance in the room.

EEC can review filter construction, media, sealing arrangement, and available test evidence against a stated efficiency requirement; referencing a standard here does not state that every EEC configuration is certified to it.