This document outlines the importance of conductivity in multi-pass filter testing per ISO 4548-12. This information also applies to filters tested per other multi-pass filter test standards, such as ISO 16889 and ISO 19438. Filters tested according to each method can experience similar changes in performance during the fluid conductivity changes outlined within this document.

The objectives of this document are to clarify the following issues:

—    Examine how conductivity affects filter capacity test results when filters are tested per ISO 4548-12:2017.

—    Compare findings to ISO 4548-12:2017 operating parameters.