European Standard for HEPA & ULPA Filters
• On a flat sheet of media, the MPPS is determined for the given media velocity. This can be done with a laser spectrometer or a combination of electrostatic classifier and CNC (Condensed Nucleus Counter).
• The filter is assembled with the specified media grade and amount of media to comply with the defined media velocity.
• The filter is challenged with an aerosol and at the MPPS both the local and overall efficiency are determined with either a CNC or laser spectrometer.
• Leaks are specified as maximum allowable local penetration at the MPPS and must not exceed 5 x the overall penetration.
• The filter is classified according to the test results in the range H10 - H14 for HEPA, U15 - U17 for ULPA.
Efficiency (%) at the MPPS Penetration (%) at the MPPS
Overall Value Local Value Overall Value Local Value
H10 > 85 - 15 -
H11 > 95 - 5 -
H12 > 99,5 - 0,5 -
H13 > 99,95 99,75 0,05 0,25
H14 > 99,995 99,975 0,005 0,025
U15 > 99,9995 99,9975 0,0005 0,0025
U16 > 99,99995 99,99975 0,00005 0,00025
U17 > 99,999995 99,9999 0,000005 0,00001
• Filters in the class H10, H11 and H12 do not require verification of local penetration.
• Filters in the classification H13 and H14 may, as an alternative, be verified with the visual oil-smoke test (previously known
as DIN 24.184), which is accepted as equal or more searching than the specified local penetration.
• U17 is an exception to the rule. In this case local penetration may not exceed 20 x the overall penetration value.