Reporting to A

Reporting to A or Standard Area is the most common so let’s start there. Your test part likely doesn’t have a surface area of exactly 1,000cm2 and while you must report to the Standard Area of 1,000cm2 it isn’t critical to test exactly 1,000cm2 of area to accomplish correct reporting. If you have a part which is larger than 1,000cm2 then typically you test one part at a time and your report will show a Total Particle Count (all particles in that size range on the filter patch) and also a Standardized Count which means that the Total Particle count is mathematically extrapolated to show the Particle Count per 1,000cm2. If on the other hand your parts are very small then best practice is to test a batch of parts with a combined total surface area of at least 250-500cm2 – whether that means testing a batch of two parts or a batch of one hundred or more parts. You want accuracy and to get accuracy you need to test enough surface area so that any part to part cleanliness variation is covered within the batch. A distinct advantage of reporting to A is that the same code or Limits can be fairly applied to parts of vastly differing size which require the same level of cleanliness. Reporting to A also allows you to very directly compare cleanliness levels of parts which greatly vary in size. By way of example if a very small part which has a bright shiny finish is testing at CCC = A(C-E15/F-G10/H-I4/J-K00) and a larger part with a dull finish is testing at CCC = A(C-E10/F-G8/H-I4/J-K00) then despite that shiny small part possibly “looking cleaner” the larger dull finished part is actually much cleaner (in this example.) Having the means to directly compare cleanliness across parts of differing size helps you to assess your cleaning operations and find ways to improve cleanliness when test results indicate the need. When gravimetric results (Mass of contamination) are also given on a “reported to A” ISO 16232 report they should be reported to A as well so that milligrams per 1,000cm2 are shown and clearly labelled as such. The Contamination Level code found in Table 2 of ISO 16232-10 is used when reporting to A or Standard Area.