Filter classes history
Classification of EPA/HEPA/ULPA Filters:
The most acceppted international standard for the filter classification of HEPA an ULPA filters is the "EN1822" developed from the european standardisation institute.
The standardised test defines minimum inital efficiencies for each filter class and attests "free of leakage".For the test a special DEHS test aerosol is to be used. On the filter inlet side the particle number concentration is measured with the particle counter. On the pure air side the scanner scans the whole filter surface. The probes suck off a certain air quantity on the pure air side of the filter and scattered-light-particle counters counts the particles passed through the filter. On this way the local penetration grade and the local filtration efficiency is determined. The norm shows the allowed penetration grade for each filter class.Finally, the whole penetration value is to be calculated.The integral value is the arithmetic mean of the local values.
On a certain air volume rate follwoing parameters are to be checked:
- Filter efficiency on MPPS „Most Penetrating Particle Size“
- Local efficiency on MPPS
- free of leakage for H13 and higher classes
- Pressure drop on nominal air flow rate
For more information see "CLEAN ROOM"
The revised version of the EN1822:2008 was accepted. Now it must be implemented into national Standards.
The end user will realize this change when they see the new names for the filter classes E10, E11 and E12. This is a new group named EPA Filters –Efficiency Particulate Air filters. (old names H10, H11, h12)
Following changes to the old standard EN1822-1:1998-7:
- Alternative test procedure – solid instead of liquid test aerosol (for leak test in case when DEHS test is critical for the application)
- Test procedure for classifying filters with membrane medium
- Test procedure for classifying filters with synthetic medium (unloaded)
- New group "E" EPA Filters –Efficiency Particulate Air filters (single tests not necessary)
- Alternative test procedure for leak tests of filters of group “H”. When the standard scan test is not practical.
filtex® is testing in conformity of the new standard. Product coding is corresponding.