What standards apply to Patch Test Kit design and testing?

 Patch tests to analyze hydraulic fluid contamination are governed by ISO 4405 (gravimetric determination of particulate contamination), ISO 4407 (particle counting with an optical microscope), and ARP-598 (aerospace fluid contamination), as well as ASTM D2276, ASTM F311, and MIL-STD/Federal Standards 791a, offering specific and complementary procedures for industry. These standards outline how fluid samples are filtrated on a membrane and how the "patch" is examined or weighted and how results are presented so that the data on cleanliness are comparable between technicians, labs, and equipment manufacturers.

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