QUALIFICATION/VALIDATION AND MONITORING
We are often asked about the relative importance of cleaning method qualification (aerospace, military, and some other groups like that term) or validation (for biomedical devices, pharmaceutical applications, etc.) and ongoing monitoring. Both are important and we suggest you monitor using a subset of the tests that are performed for qualification/validation. Even more important, as we recently explained,¹ plan the validation/ qualification during development of the critical cleaning method.

Even if the process is running smoothly, keep an eagle eye out for cleaning process changes both inhouse and by your components suppliers, and for formulation changes by manufacturers of cleaning chemicals and process chemicals. Determine what might be a problem. Monitor appropriately; and, if there appears to be a problem, revalidate.

CRITICAL CLEANING
Identify, then qualify/validate and monitor the critical cleaning steps. The terms critical cleaning and precision cleaning are often used interchangeably. We have a preference for the term critical cleaning. Precision cleaning conjures up a vision of cleaning in a highlyrestricted cleanroom. Perhaps each individual component is cleaned separately by a highly-trained technician; perhaps there are wet benches with automated product handling; maybe there is a multi-chamber automated spray system that feeds directly into the cleanroom. This is a limited view of the important cleaning step. In our experience, the important cleaning step, the critical cleaning step, may occur in a machine shop or in a job shop (eg. a coating facility), in what looks at first glance like an automotive repair facility. If the soil (matter out of place) is not adequately removed at that step, subsequent cleaning steps may not resolve the problem.

Subsequent processing and cleaning may actually exacerbate contamination by inadvertent chemical reaction of the soil, drying of the soil, or by embedding the soil in the surface of product. Contamination happens long before the product enters the cleanroom. A cleanroom can minimize recontamination, but the most sophisticated cleanroom or controlled environment may not correct a contaminated product.

MONITOR APPROPRIATELY
As with cleaning, more testing is not always better. Whether the issue is validation/qualification or monitoring, select the appropriate tests. This involves re-enacting that venerable game of “Animal, Vegetable, or Mineral.” Consider what might have to be tested.