PTFE Membrane HEPA / ULPA Filter (Boron-Free, Low Pressure Drop)

The difference is how particles are captured. Glass-fiber media is a fiber mat about 0.4–0.6 mm thick that captures particles layer by layer through its depth (depth filtration). PTFE is stretched into a microporous membrane laminated to a non-woven support, and most particles are stopped at the membrane surface (surface filtration). The thin membrane and very fine fibrils give low airflow resistance at the same efficiency; patents and academic studies put the pressure-drop ratio at about 1/2 to 2/3 of glass fiber. On this page, the 69 mm H14 PTFE-MH995-570-1170-69 runs at about 58 Pa at 0.45 m/s and the 50 mm U15 PTFE-MU9995-570-1170-50 below 73 Pa, while glass-fiber mini-pleats of the same depth are usually 50% or more higher. Lower pressure drop lets FFU fans run slower and save energy, or deliver more airflow with the same fan.

Glass fiber in conventional HEPA / ULPA filters is borosilicate glass. Hydrofluoric acid vapor from etch and cleaning areas attacks it and produces boron-containing gases such as boron trifluoride (BF₃) that travel with the airflow into the cleanroom. Boron is a p-type dopant for silicon, and when it deposits on the wafer surface it changes device electrical characteristics. The binder in glass-fiber media can also release organics that become part of the AMC (airborne molecular contamination) load. A PTFE membrane contains no boron, phosphorus or metals, needs no binder and resists HF, so lithography, etch and thin-film areas commonly specify U15–U17 PTFE ULPA. Note that frame potting and gaskets can also outgas, so when specifying boron-free, ask for the outgassing specification of the complete filter.

Yes, but at a lower concentration. Because PTFE filters at the surface, oil aerosol forms a film on the membrane and blocks its pores, permanently raising pressure drop; the upstream concentration of 10 µg/L or more commonly used with the photometer method is too heavy for PTFE. Use the particle-counter scan method with upstream PAO kept to a few µg/L or less, or use solid PSL latex spheres as the test aerosol, and keep scanning time short. Every filter on this page is scan-tested before shipment with a report; if your field acceptance must use the photometer method, please confirm concentration and duration with us first so pressure drop does not jump before the filter even goes into service.

In clean recirculated cleanroom air the two last about as long, and PTFE can last longer because it is not brittle and does not shed, so fewer tears occur in handling and installation. The real weakness is dust-holding capacity: the membrane collects dust only on its surface, and research has measured about 1 g/m² for a bare PTFE membrane and only about 6 g/m² with a melt-blown layer added, far below glass fiber. An F8–F9 medium pre-filter upstream is therefore essential, and outdoor-air units need an extra coarse stage. Replace at twice the initial pressure drop; for example, PTFE-MU9995-570-1170-50 starts below 73 Pa, so plan replacement at around 140 Pa.

EN 1822 and ISO 29463 measure efficiency at the MPPS (most penetrating particle size, typically 0.1–0.25 µm), because particles larger or smaller than this are easier to catch, so testing at the hardest size represents the worst case. Each grade step cuts penetration to one-tenth: H13 allows 0.05%, H14 0.005%, U15 0.0005%, and U17 only 0.000005%. In practice, pharmaceutical aseptic areas and ISO 5 cleanrooms use H14, semiconductor back-end and display fab FFUs mostly use U15, and front-end lithography and etch areas at ISO 3–4 use U16–U17. Higher grades mean higher pressure drop: about 58 Pa for the 69 mm H14 on this page and about 97 Pa for the 90 mm U17 PTFE-MU999995-570-1170-90, so confirm that the fan has enough static pressure.

Model codes match our ERP item codes. Take PTFE-MU9995-570-1170-70: PTFE means PTFE membrane media, M is mini-pleat, U is ULPA (H would be HEPA), 9995 is the digits after "99." in 99.9995% efficiency, and the numbers that follow are width 570, height 1170 and depth 70 mm. So MH95 is 99.95% (H13), MH995 is 99.995% (H14) and MU999995 is 99.999995% (U17). Models marked * are standard specifications numbered by the same rule; their pressure drops are typical values and the order specification sheet governs. Sizes, depths and frame types can all be made to drawing.

Yes. PTFE media is available in sheets: PTFE99-1.2-1.2 is a 1.2 × 1.2 m sheet of 99.99% grade, about 90 g/m² and 0.45 mm thick, with about 145 Pa pressure drop at a media velocity of 5.3 cm/s. For higher efficiency there is the 99.999% grade PTFE999-1.2-1.2 (about 200 Pa, made to order). This suits customers with their own pleating equipment or who make small in-equipment filters and vent filters. We can also cut it to size, or pleat and frame it into finished filters for you.

If there are no acid gases, the process is not sensitive to boron or organic outgassing, and the fans have plenty of static pressure in reserve, glass-fiber HEPA / ULPA filters cost less and hold more dust, so total cost of ownership is usually lower, for example in general hospital wards, food plants and electronics assembly lines. PTFE is worth switching to in semiconductor and display front-end processes, recirculation and exhaust areas with HF or acid / alkaline gases, large ceilings where FFU energy use needs to come down, and high-humidity environments. A practical approach is to switch the most sensitive areas or the most energy-hungry FFU groups first, then decide whether to expand based on measured pressure drop and electricity data.