What does ISO Class mean?

All products used in cleanrooms need to fulfil the same requirement:

During operation, as few particles as possible should be released into the surrounding area. This is especially applicable for moving machine parts such as energy chains and cables. To generate as few particles as possible requires high abrasion resistance, and is therefore also an indicator for long service life. This is a development goal for all igus products. igus tests each of its products in elaborate long term test procedures in its own laboratory. Only what meets the standards of our laboratory is then selected for the Fraunhofer IPA tests.
The evidence is supplied by a new expert’s report from IPA, the Fraunhofer Institute, by which numerous igus products are certified with the best classification possible, ISO class 1: