The oil thread test mentioned in ISO 1822-4, annex A is used for visual proof of the absence of leakage of HEPA filters. This simple quality test procedure may be an alternative to the scan method.
The oil thread test (DOP Test) is also applicable if the scan method is not fully applicable because of the filter design (e.g. V-shaped arrangements).
For scanning of HEPA and ULPA filters, Topas offers the Filter Scanning Test Rigs AFS 150 and AFS 152 – well proven and reliable solutions.
Principle
The filter element (sample) is mounted horizontally with the upstream side down on the test bench and secured with a pneumatically operated fixing device. For testing, the filter is then exposed to a flow of a polydisperse aerosol of oil droplets (DEHS).
An existing leak is made visible on a rising oil thread on the downstream side (upper side) of the filter.
