Fiter classes history

EN779 ... ISO16890

New EN779:2012:

By the end of March, 2011 the new issue of the EN779 was accepted. The new name is EN778:2012. In particular the test method for fine dust filters F7-F9 changes.  Minimum filter efficiencies are defined. (same values as SWKI) The filter is to be tested in unloaded condition.

 The most important changes at  first sight:

  • Minimum efficiencies for classes F7-F9 (unloaded condition)
  • No limits for F5 and F6
  • Renaming…the filter class F5 becomes M5 and F6 becomes M6

 It will run problems to fulfill the new standard with  pocket filter made of synthetic media but it is no problem with  fibre glass media. It is also not possible to give reliable predictions from the test results to practical use. filtex®  already fulfils today the demands of the new Standard with the product line "doubletex" with synthetic material, as well as with the product line "glass" with fiberglass medium.

Minimum filter efficiency:

Filter arrestande and efficiency are average values.
Coarse dust filters up to class G4 are tested up to the final pressure of 250Pa. Then the middle filtration efficiency is determined. Fine dust filters of classes F5 to F9 are tested up to the final pressure drop of 450Pa. Then the middle efficiency is calculated.

In practice filters are often changed before the final pressure drop is reached. The result is, that in these cases one must assume  that the demanded filter class is not reached at all.
The initial efficiencies  of pocket filters can lie far under the stated average value of the filter class.  In order to reduce the mean variation the swiss national norm institute SWKI has fixed values for minimum  initial efficiencies. The illustration shows the accepted minimum efficiencies of separate filter classes according Swiss norm EN779 / SWKI VA101 (0.4ym particle DEHS)

International standard for the classification of air filters:

The most accepted international standard for classifying  coarse- and fine dust air filters is the EN779. This testing method was revised in 2003  (issue EN779:2002)

The goal was to adapt the test method more to the practical conditions to be able to make predictions for the practical use of the filters.
But praxis learns us that such comparisons are almost impossible.
Experts agree that serious declarations of filter performance can be done only by running comparison tests. The aerosol conditions in praxis applications are too different.

Test institutes:

Wll known institutes for tests and classifications of air filters:

  • AFTL: Air Filter Test Laboratories USA
  • FIATEC: Filter an Aerosol Technologie GmbH Deutschland
  • SP: Technical Research Institute of Sweden 
  • VTT: Technichal Research Institute of Finland