Cleanroom Filters — High-Efficiency HEPA / ULPA

HEPA filters (High Efficiency Particulate Air) and ULPA filters (Ultra Low Particulate Air) are the core filtration components for high-cleanliness environments. Under EN 1822, HEPA covers H13 (99.95%) and H14 (99.995%); ULPA covers U15, U16, and U17, reaching efficiencies up to 99.999995%. The widely-mentioned H10, H11, and H12 grades are classified as EPA (Efficient Particulate Air) under EN 1822, with efficiencies from 85% to 99.5%, and are typically used as pre-filtration. HEPA filter testing is based on MPPS (Most Penetrating Particle Size, approximately 0.12–0.25μm), which most accurately reflects actual filter performance at the most difficult-to-capture particle size range.

Specification options include standard aluminum-frame gel-seal type, knife-edge seal type, stainless steel corrosion-resistant type, and dry-box type, with aluminum foil or hot-melt adhesive line separators, or separator-free construction. Under EN 1822, every H13-and-above filter is leak-tested individually with its own test report; the PTFE series is scan-tested unit by unit, and report contents for other series are confirmed per model. Selection must consider rated airflow, initial pressure drop, frame material compatibility, sealing mechanism, and test methodology.

Besides standard glass-fiber media, PTFE membrane media is also available: initial pressure drop is only about 1/2 to 2/3 that of glass fiber at the same grade, it contains no boron or phosphorus and resists acids, alkalis and moisture, making it suited to semiconductor and display areas sensitive to boron release and AMC, in grades H13 to U17.

Typical applications: semiconductor front-end wafer fabrication and back-end packaging, TFT-LCD and OLED display production lines, BSL-2/3 biosafety laboratories, aseptic pharmaceutical filling zones, positive and negative pressure hospital operating rooms, and PCR testing facilities.

Cleanroom filter selection must align with ISO 14644-1 cleanliness classes: ISO Class 1–3 environments require ULPA U15–U17 filters; ISO Class 4–5 (semiconductor front-end fabs) call for HEPA H14 (99.995%); ISO Class 6 (general cleanrooms) uses HEPA H13 (99.95%); ISO Class 7–8 (packaging areas, laboratories) can use EPA-grade H10–H12. Actual selection must also consider ceiling coverage ratio, FFU recirculation ratio, and terminal installation method (gel-seal vs. knife-edge).

A multi-stage filtration strategy effectively extends cleanroom filter life and reduces total cost of ownership (TCO). The typical three-stage configuration is: pre-filter (G4) capturing particles above 5μm → medium filter (F7–F9) capturing 1–5μm particles → HEPA/ULPA terminal filtration. Medium filter quality directly determines HEPA lifespan — a well-designed configuration can extend HEPA service life by 2–3×, significantly reducing replacement frequency and downtime costs.

Besides the filters themselves, this category also includes terminal filtration units that combine filter and housing: the ceiling HEPA box mounts directly in a T-bar ceiling and connects to ductwork with flexible duct, in fully disposable and room-side replaceable versions; the hospital HEPA box is used for positive-pressure supply in operating rooms and exhaust from negative-pressure isolation wards; and the V-bank filter box arranges several mini-pleat media packs in a V to greatly increase filtration area within the same face size, suiting high-airflow air handling units.

HEPA filter grade comparison table (H10–H14 / U15) and MPPS test principle →