Plan twice; validate once is a prudent variant of the adage. Cleaning validation is a hurdle in many applications, including aerospace, microelectronics, pharmaceuticals, and medical device manufacture.

The term “validation” is often associated with life science applications that are regulated by the FDA or analogous agencies world-wide. We choose to broaden the use of the term to include verification and documentation of cleaning processes in any industry that produces critical product. In this broader context, cleaning validation involves assuring the efficacy for the product being assembled and assuring that the product does not compromise the health and safety of either assembly workers or users of the product. In this context we are discussing cleaning, not sterilization. That is, cleaning validation means demonstrating and documenting that interfering residue, alive or dead, is reduced to an acceptable level.

The first step in validation, before any of the paperwork or signature cycles are established, is setting up an effective, rational, cleaning system. Cleaning includes washing (or soil removal), rinsing, and drying.

VALIDATING A MYSTERY
Often, we are called in at the validation stage, only to find cleaning processes that have been adopted for reasons unknown to even those most familiar to the process. We see an assortment of aqueous cleaning agents used in a variety of immersion and ultrasonic processes, perhaps interspersed with solvent spray, wipe or immersion steps, usually involving isopropyl alcohol and acetone. When we ask why the processes were adopted, we may be told that legendary engineers, half a dozen years ago, thought the processes would work. The all-important rationale has been lost in the mists of time. The processes have become set in stone; now we have one month to validate cleaning. Such mystery cleaning processes can be a challenge to validate. A report saying “nice cleaning process!” is not sufficient.