This air filter test system is designed to meet requirements of EN1822-4 Appendix E “efficiency leakage test for particle sizes from 0.3 µm to 0.5 µm”. This part of the standard is related to filter elements which cannot be scanned due to their geometrical design. In this case determination of integral filtration efficiency is sufficient for quality control.
Principle
In comparison to the alternative oil thread test procedure this method gives much more reliable and much faster results on defective filter elements. Furthermore filters are much less loaded by test aerosol from the test procedure.
The required test aerosol is produced by a special aerosol generator (ATM 221) using standard DEHS test liquid. For upstream concentration measurement an optical particle counter is used in combination with cascaded self-adjusting dilution systems (DIL 540/C). A parallel optical particle counter determines downstream particle number concentration. Resulting filter efficiency is compared to nominal filter efficiency giving a final “pass” or “fail” result to each tested filter.
