MANUFACTURING PRODUCTS & EQUIPMENT ARTICLE

Studies have shown that wiping is the most effectivemethod of cleanroom cleaning. Presaturated wipesespecially, are highly suitable for capturing andremoving particles and dirt, disturbing biofilms andremoving residues. The removal of particles isespecially key, not only to pick up dirt and particles,but to trap them in the wipe and physically removethem from the cleanroom. The ability of a wipe to retainand remove a particle or fibre depends on the structureof the wipe and the size of the contaminant.

Dry or wetted wipes for cleaning?Some manufacturers have developed proprietarysurface treatments to dry wipes in order to enhanceparticle removal and retention. Particle AttractionTechnology (PAT) enhances the ability of the wipe toattract and retain fine particles, less than 10 microns.This improves the wipes ability to clean surfaces,thereby leaving surfaces cleaner. It is a permanenttreatment that molecularly bonds to the fabric fibresand is in fact actually enhanced in the presence of asolvent.

Wetting the wipe significantly enhances particleentrapment and removal. Using a wetted wiperprovides an overpowering bias for the particles toremain with the wipe, since capillary hydroscopicforces from the moisture on the wipe provide themechanism for the particles removed from the surfaceto remain with the wipe. Once the wipe is removedfrom the environment, the particles go with it, resultingin the most effective method for removing particlesfrom a cleanroom surface.

The amount of fluid used to pre-wet the wipe iscritical: if the wipe is over saturated then particles arere-deposited on the surface and simply moved around,not picked up into the wipe1.

Advantages of presaturated wipesPresaturated wipes can offer many benefitsover bottled IPA and dry wipes for cleanroom use.Presats were first introduced to cleanrooms in IBM in1988 by Contec Inc, to reduce solvent utilisation andincrease convenience in hand wiping. Because theyprovide exceptional solvent control, presaturated wipeswere soon adopted by the aerospace, semiconductor,automotive and other industries in order to meetincreasingly stringent VOC emission and solventreduction regulations. However, one of the quickestadopters of these products was the medical deviceindustry, which saw the productivity improvements andprocess controls the technology offered. Sterile presatsfor the pharmaceutical industry were introduced in1990 and are now one of the fasting growingconsumable products used in pharmaceuticalcleanrooms due to the benefits they provide.

Solvent reduction and lowering of VOCsBased on feedback from end-users, a comparison ofcommon methods of applying cleaning solutions towipes showed that solvent usage can be reducedbetween 15 and 50% depending on the method ofsaturation. The majority of pharmaceutical cleanroomsuse 70% alcohol solutions for transfer disinfection as itis fast acting and leaves no residue. For instance, if IPAis the alcohol of choice, it has a low work exposurelimit (UK TWA 400 ppm eight hours) and this limit canbe very easily breached when spraying for long periodsof time during transfer disinfection. The use ofpresaturated wipes can eliminate the need for costlyremedial work to install ventilated transfer hatches.

Process control and repeatabilityIn all cleanrooms there is a need for repeatable andvalidated processes. The spraying of a dry wipe with asolvent to a predefined saturation level is not arepeatable process. Each operator has a different viewon when a wipe feels wet. Add to this that the operatoris probably wearing two pairs of gloves and thetendency is to over wet the wipe as they cannotactually feel how saturated (or not) the wipe is. Eventhe same operator on different days probably does notsaturate a dry wipe in the same way.

In the case of disinfection, the objective is to leave avisible film of disinfectant on a surface for a definedcontact time. The wipe needs to be saturated enoughto leave behind enough disinfectant, but not be so wetthat the benefits of controlled application of the fluidare lost. Also, the validated process of disinfectionrelies on the correct amount of disinfectant beingapplied by each operator to get the expected logreduction in microorganisms. If insufficient disinfectantis applied, the disinfectant may dry before the validatedcontact time is reached.

In the case of cleaning, the saturation levels are evenmore crucial. A groundbreaking study by Mattina et al2showed that a wipe saturated beyond its ability to holdsolution, left a surface with more contaminants thanwith any other level of saturation. Indeed, saturationlevels below the saturation limit (i.e. a less wetted wipe)consistently resulted in fewer particulate contaminantsremaining on the wiped surface. A wipe with excesssolution will leave some solution behind on the wipedsurface and with it any contamination within thesolution.

ValidationHaving a validated cleaning process requiresdocumentation of both the process and the products

used in the process. The use of a presaturated wipereduces time and costs as only one product, thepresaturated wipe, needs to be qualified and validatedas opposed to two products, the wipe and the spray.Using presaturated wipes simplifies the writing of SOPsas the process of validating the spraying of the wipe isremoved. This saves time, but more importantlyprovides a process that is more easily audited byinternal and external agencies.

DisinfectionAnother more recent study also came to agroundbreaking conclusion. A study published inLetters in Applied Microbiology3 compared the spreadof microbial contamination on surfaces cleaned withdry wipes that were sprayed with alcohol with thosecleaned with presaturated wipes. This independentstudy concluded that wiping with presaturated wipesminimised the spread of contamination: “The dry wipessprayed with alcohol demonstrated minimal effect atreducing the bacterial bioburden on a surface andwere able to transfer viable micro-organisms betweensurfaces… However, the continuous transfer of bacteriafollowing the use of the dry wipes sprayed with alcoholis of concern. …our results clearly demonstrated, in aquantitative manner, that alcohol pre-impregnatedwipes are more effective at reducing surface bioburdenthan dry wipes sprayed with alcohol.”

ConclusionCleaning and disinfection in a pharmaceuticalcleanroom is a critical process to protect patient safetyand product quality. More effective and consistent handcleaning and disinfection will result in greaterconsistency, quality and safety in the overall processand the resulting product. Damp wiping to a validatedprocedure is a proven method of effective surfacecleaning versus other techniques. The use ofpresaturated wipes brings additional benefits inimproved productivity, reduced validation, increasedprocess control and repeatability, improved safety andVOC reduction. For life science cleanrooms, the use ofalcohol presaturated wipes versus wipes wet at point ofuse is even more beneficial as it has been proven thatthey are more effective at reducing surface bioburden.

References1. Wiping Surfaces Clean Vicon Publishing 2004: HSiegerman Ph.D.2. The cleanliness of wiped surfaces: particles leftbehind as a function of wiper and volume of solventused. C F Mattina, J McBride, D Nobile Cleanroom EastProceedings 1996.3. Evaluation of alcohol wipes used during asepticmanufacturing. The Society for Applied Microbiology,Letters in Applied Microbiology 48 648-651. M.N.Panousi, G.J. Williams, S. Girdlestone, S.J. Hiom and J.-Y. Maillard (2009).The author would like to acknowledge the input of JackMcBride and Dave Nobile of Contec Inc. in compilingthis article.

Wipe with PAT

Wipe without PAT

Author: Written by Karen Rossington, freelancemarketing consultant to contamination controlspecialist Contec Inc., www.contecinc.com.

Successful Wiping

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