This test method applies to particulate airfilters (HEPA) and high-performance particulate airfilters (ULPA) in room and process air technology, e.g. in clean room technology. It lays down a method for testing the filtration efficiency on the basis of particle counting methods using a liquid test aerosol and allows uniform classification of the particulate airfilters according to the filtration efficiency.
The degree of fraction filtration efficiency for nominal filter medium speed is determined for a particle size range using the flat, unfolded filter medium. The particle size at which the filter shows its minimum filtration efficiency (Most Penetrating Particle Size = MPPS) is determined from the fraction interception curve.
The filter element is checked for leaks with a test aerosol, whose average particle size corresponds to the MPPS. At the same time, the integral filtration efficiency is determined.
On the basis of the values determined for the local filtration efficiency and the integral weight arrestance, the filter can be assigned to a filter class according to the table above.