CM/Spotlight: Safety about 1 outermost layer of epithelial cells per day ■ A skin cell is about 33 micrometers by 44 micrometers — a size just under the ability to be easily seen by the naked eye ■ About one in 10 skin cells carry bacteria ■ Some species of bacteria deposited on surfaces via skin particles can remain viable for months and even years. Consequently, major contributors to both particle and bacterial contamination are the workers themselves going about their normal tasks. And, as long as human beings are in workspaces, there is nothing that can be done about their being sources of this contamination. Unless airborne skin particles are removed by a HEPA-filtered HVAC system, they will eventually settle on vertical and horizontal surfaces. Once settled on these surfaces, the skin and other particles must be removed by efficient cleaning methods or the contamination, along with contamination from other sources, will spread through a whole facility by normal human-surface contacts. In cleanrooms, this particle contamina-tion is reduced by HEPA filtering of the air within the room, by garments — includ-ing face and hair masks and shoe cov-erings — worn by the workers and by rigorous cleaning routines all governed by protocols written for each individual facility to conform with international speci-fications. In pharmaceutical cleanrooms, an inde-pendent quality control (QC) department is often tasked with monitoring the clean-room, which means testing the level of air-borne and surface contamination for both particle and bacterial content. Airborne particle and bacterial densities are usually checked both in the presence and absence of workers, while surface contamination monitoring is done both before and after cleaning. The success of this system of mainte-nance for pharmaceutical and semicon-ductor cleanrooms is demonstrated by the low particle density levels in cleanrooms. is to where we want it to be 3. Soil is never destroyed, always cre-ated and often relocated. It follows from these laws that: ■ Since soil isn’t destroyed by a clean-ing solution, when you mix rinse solu-tions with a cleaning agent, you’re just recycling soil ■ One can never get surfaces com-pletely clean: If a perfectly clean sur-face meets a cleaning agent contain-ing even one molecule of soil, that soil molecule can be transferred back to the clean surface and contaminate it. As an example of the practical applica-tion of these laws in cleanrooms, moist-ened cleaning wipes used to clean sur-faces are refolded after a set number of wipes to expose a clean wiping area to the surface. And, after a set number of foldings, the wiper is replaced by a clean wetted wipe. The operations are done according to rules established for each working area. Another example is that if mop cleaning is used for cleanroom floors, it has been found that the three-bucket system is preferable to the two-bucket system; rules are established for how many changes of cleaning and rinsing solution must be done for a given floor surface area. Also, the wiping parts of the mops them-selves are subject to being discarded after a set number of uses and are made of materials that optimize absorption of contamination. In addition, some facilities are finding that eliminating mopping altogether by adopting spray-and-vacuum technology solves many cleaning problems. Finally, there is a point that even some cleanroom maintenance professionals neglect: Cleaning a surface without rinsing it leaves residues that may not only lead to further contamination sticking to the surface, but may also damage the surface. Using OPCs judicially, using wipes cor-rectly and mopping or otherwise removing soil in optimized ways are just a few of the many procedures used in all well-main-tained cleanrooms that could be adapted to commercial cleaning environments to improve cleaning efficiency and reduce contamination. CM Learning From Cleanrooms As mentioned, some technologies, such as HEPA-filtered HVAC systems, are not practical for non-hospital settings due to installation expense and upkeep. Likewise, the use of special garments is not practical outside of a hospital environ-ment. Conversely, practical steps within the capabilities of almost any facility interested in using the principles for keeping clean-rooms clean include: ■ An understanding of the major sourc-es of particle/microbial contamination in an individual workplace ■ The development of written specifica-tions for cleaning performance and rigorous monitoring of the actual per-formance. Handheld airborne particle counters, also called optical particle counters (OPC), are easy to operate, stable and useful tools for determining the magnitude of airborne contamination problems in work-ing spaces. Remembering that airborne contamina-tion rapidly becomes surface contami-nation, OPCs can be used to determine amounts of contamination coming from existing HVAC systems: That is, OPCs can be used to determine where some basic air filtering could reduce major amounts of airborne contamination entering the workspace. OPCs can also be used to determine what portions of workspaces are major sources of par ticle contamination — equip-ment, unusual human activity, etc. — that could therefore be sealed off or otherwise contained. Thus, using OPCs could save money and increase cleaning efficiency by showing where airborne contamination that eventu-ally settles on surfaces can be reduced. As far as cleaning operations go, a realization of the basic “laws” of cleaning should be understood by groups in charge of maintenance. These laws are: 1. Whenever a surface becomes clean, something else becomes dirty 2. Cleaning just moves soil from where it 34 CM/Cleaning & Maintenance Management ® • November 2011
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