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AFS 155 – Oil Thread Leak Test System

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.


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.

  • Cost-effective solution for leak testing of filters ranging up to group H (filter class H13 and H14)
  • Easy manual operation
  • Constant test conditions according to EN 1822-4 due to pre-adjustable test parameters
  • Effective testing of larger numbers with pre-adjusted test parameters
  • Flexible and easily configurable filter holder in case of different filter dimensions
  • Portable due to compact size
AFS 155 - Oil Thread Leak Test System
Filter dimensions in mmMin. 305 x 305 x 30
Max. 915 x 800 x 300
Air flow50 .. 600 l/min
Diff. pressure0…1000Pa (0.15psi) ±2%
Filter face velocityca. 1.3 cm/s
Aerosol concentrations1.5 g/m³
Aerosol substanceDEHS
Pressurized air supply6 bar
Power supply230VAC/50Hz/1A
Dimensions in mm910 x 1200 x 610
Space requirement100 x1 200 x 1500

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