The European standardisation body, has launched EN 1822 for classification and testing of HEPA and ULPA filters based on filter efficiency at the most penetrating particle size (MPPS).
Testing per EN 1822 is normally done with an aerosol probe which can be moved over the entire surface of the filter. This moving of the aerosol probe, or scanning, results in the measurement of many local collection efficiencies. These local efficiencies can be used to calculate the overall efficiency of the filter or the "leak rate" of a specific area of the filter. The overall efficiency calculation is often termed the integral value, while the leak rate is often termed the local value.
The following table shows the various classifications of high-efficiency filters per EN 1822:
| Integral Value | Local Value | |||
|
Filter Class |
Collection Efficiency % | Penetration % | Collection Efficiency % | Penetration % |
| H10 | 85 | 15 | - | - |
| H11 | 95 | 5 | - | - |
| H12 | 99.5 | 0.5 | - | - |
| H13 | 99.95 | 0.05 | 99.75 | 0.25 |
| H14 | 99.995 | 0.005 | 99.975 | 0.025 |
| U15 | 99.9995 | 0.0005 | 99.9975 | 0.0025 |
| U16 | 99.99995 | 0.00005 | 99.99975 | 0.00025 |
| U17 | 99.999995 | 0.000005 | 99.9999 | 0.0001 |
Tests are performed on new filters at specifiec nominal volumetric airflow. Filters of U15 or above must be scanned with a particle counter probe designed for this purpose. An oil thread test can be utilized on filters of H13 and H14 classification.
Filter testing includes measurement of the following:
- pressure drop at nominal airflow
- overall collection efficiency at most penetrating particle size (MPPS)
- local collection efficiencies at MPPS
- no leaks above H13 as specified in the table above
Camfil Farr manufactures Megalam (HEPA/ULPA) filters to the most stringent industry and/or customer standards. We also test raw material components for ”outgassing” e.g. organophosphates from PU sealants. Solid latex spheres or silica are normally chosen as test aerosols for the microelectronic industry due to their low ”outgassing” properties. Camfil Farr has a policy of continuous improvement as a means of insuring our leadership position in the high efficiency filtration market- place. We maintain extensive joint R&D programs with our key suppliers to develop and test next generation filtration media. Such efforts allow us to provide the highest performing filtration products to meet the demands of emerging technologies.
Camfil Farr was the first to provide U17 grade ULPA filters utilising ”low boron” media. We also manufacture e-PTFE filters in grades U15 and higher.