The filter medium is clamped in a special filter holder, which guarantees the secure and tight fit of the test object during the test. With a few simple steps, the filter holder is removed from the test channel to change the filter medium or to determine its mass. A support grid prevents strong deformation of the test specimen at high flow rates. The final filter (absolute filter) downstream of the test filter can also be easily installed and removed for mass determination.

The fractional efficiency is determined with an optical particle counter LAP 340 in a particle sizes range of 0,2 to 10,0 µm. The sampling between upstream, downstream and purge is controlled by and sample switching unit SYS 520. This means that only a single particle measuring device is required. The switching time of the sample switching unit SYS 520 is freely adjustable by the user. If required, a Topas dilution system series DIL 55x or an aerosol spectrometer LAP 322 with a particle size range from 0,2 to 40 µm can be supplied.