European Standard for EPA, 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 E10 - E12 for EPA (Efficiency Particulate Air Filters), H13 - H14 for HEPA (High Efficiency Particulate Air Filters), U15 - U17 for ULPA (Ultra Low Penetration Air Filters).
||Efficiency (%) at the MPPS||Penetration (%) at the MPPS|
|Overall Value||Local Value||Overall Value||Local Value|
• Filters in the class E10, E11 and E12 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 oil thread 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.