It is no doubt that many of you have consider about which supplier or manufacturer provides the best absolute filter cartridge. And Can they actually meet the absolute filtration requirement? Which filter cartridge is truly absolute filter cartridge? You might think that it is troubling to figure out all these questions.

How to do absolute filtration efficiency testing

But what customers think about is what Brother Filtration going to do. In this article, we will answer all these questions, and let you know how to test the filtration efficiency.

What is absolute filtration? And what is the absolute rating?

Absolute Filter Rating: Filter rating meaning that 99.9 percent—or essentially all—of the particles larger than a specified micron rating will be trapped on or within the filter.

What is absolute filtration And what is absolute rating

The diameter of the largest spherical glass particle that will pass through the filter under laboratory conditions is often given in micrometers (mm) and is referred to as the absolute rating, or cut-off point, of a filter.

It displays the filter medium’s pore opening size. Theoretically, filter media with a precise and constant pore size or opening have an exact absolute rating.

The largest glass bead that will pass through the filter at extremely low-pressure differentials and non pulsating conditions is what the absolute rating simply determines. This is not to be confused with the largest particle that will pass through a filter under operating conditions.

Testing method

There are 2 methods to do “absolute filtration efficiency testing” for PP(polypropylene)cartridge filter ( here we use our high flow cartridge filter for example).

Testing method 1 — ISO 121031 A4 dust

ISO 121031 A4 dust

What is ISO 121031 A4 dust?

ISO 12103-1 A1 ultrafine test dust with a nominal size between 0-10 microns. This dust was originally developed for car’s air filter trials.

Although it is not currently suitable for the inspection of car air filters, it is used for fuel system components, water filter performance evaluation, and other applications.

ISO ultra-fine test dust is a product obtained by grinding and sorting techniques to obtain a smaller sub-micron composition than ISO 12103-1 A2 fine test dust.

Normally speaking, PP liquid cartridge filter can be easier to pass ISO 121031 testing, the result always shows Absolute Filtration efficiency of 99.98%, but sometimes in liquid separation, the filtration efficiency can not reach that high.

Testing method 2 — Liquid separation & filtration

A method for characterizing the pore size of a microporous membrane, the method comprises the following steps:

Liquid separation & filtration
  1. Artificially modulated spherical SiO2 microspheres with a normal particle size distribution, It was formulated as a 10wt% suspension;
  2. Microporous membrane filters the suspension, Simulated raw water experiment;
  3. The particle distribution in the filtrate before and after filtration was tested by a laser particle size analyzer;
  4. Fitting conversion and drawing are carried out to the SiO particle size distribution data after filtration
  5. Finally, the tester will dry the liquid filtered, and compare the quality change between filtration before and after.

How does Brother Filtration conduct the absolute filtration efficiency testing of PP high flow cartridge filter?

According to method 2, we did a test about absolute filtration efficiency.

Is there a testing report? And how to understand?

Through method2, we can get the filtration efficiency performance based on each membrane layer, which shows below.

The charts show the short reporting of our test result, if you want to read the whole test report, please feel free to contact us.



As the increasing demands for absolute filtration, more and more filter cartridges or bags with absolute ratings have come into the market. It is difficult for consumers to distinguish the quality and efficiency of filter cartridges from their appearance. So, we give methods to solve this problem.

Brother Filtration has years of filtration experience, designs and manufactures all kinds of filter products, and offers filtration solutions to various industries and applications. If you have any filtration problems, please feel free to contact us, and our professional technical team will help you.

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