The ex-regulator’s view on small surface contamination control: It’s just a bit of wiping, right?

Published: 31-Jan-2025

Ecolab Life Sciences’ Matt Cokely and Rose Pharma Solutions’ Phillip Rose discusses the under appreciated role of disinfecting “small surfaces”

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You may have thought by now we had said everything we need to say about cleaning and disinfection of small surfaces in cleanrooms, and material transfer of items. After all, it’s just a bit of wiping, right? 

For their respective roles, both authors have visited (and continue to visit) cleanrooms of sites around the world, often reviewing their cleaning and disinfection practices.

Small surfaces can often be intricate or complex

All too often, poor practice, badly designed regimes and common mistakes are still seen. In this article we will summarise some of the most pertinent regulations and best practice guidance related to small surface disinfection and material transfer. 

Back to basics

Cleaning and disinfection are two distinct tasks, with different aims. Cleaning (often using a detergent) is designed to wet and/or emulsify dirt, soiling or residues to aid their removal.

Whilst it may reduce microbial levels present, this will not be to the same extent as a disinfectant.

Disinfection is designed to reduce the levels of microorganisms on a surface through the chemical action of the agent on microbial cells. To be most effective, disinfectants should be applied to a clean surface. 

By clearly defining these processes in the SOP and being clear about when a surface or area is being ‘cleaned’ or ‘disinfected’ we can help ensure that surfaces are being maintained in a clean, residue controlled and low bioburden status. 

We often see end users only using alcohol on small surfaces

Similarly, defining the techniques and equipment that should be used on different surfaces is important. Clear SOPs, detailed logbooks, and rigorous, well-designed training can prevent ambiguity and ensure that the regulatory requirement to adequately control this activity is met. 

We flippantly posed the question that “It’s just a bit of wiping, right?”, but we should keep in mind that small surfaces, whilst ubiquitous in cleanrooms, can sometimes be some of the most critical areas due to their proximity to the final drug product. 

In both EudraLex Volume 4 Chapter 3, and Annex 1 it is made clear that cleanroom surfaces should be cleaned and, where applicable, disinfected thoroughly according to detailed written procedures or programmes. 

The criticality of the surface should inform the frequency of cleaning and disinfection. ISO 14644-5 identifies wiping as the predominant technique for small surfaces. 

It is usually advocated that any wipes used should be folded to roughly hand size

Small surfaces can often be intricate or complex – and can include items such as tables, trollies, swivel chairs, or external surfaces of equipment.

Whilst we have seen that the regulatory requirement is to ‘clean and/or disinfect in accordance with detailed written procedures’, little is said in terms of how to do this in practice. It is again useful to turn to the ISO standards, where section F.4.8 suggests appropriate wiping technique, and recognises the complexity of disinfecting carts, trolleys and wheeled equipment. 

It is important to describe in detail the appropriate and approved detergents and disinfectants to use. This description should also include specifying the approved vendor, setting out the frequency of use, describing the rotation schedule, wet contact times and residue control steps for cleaning and disinfection processes. 

These elements, along with details of the saturation levels of wipes to be used, folding, wiping technique, number of strokes per wipe face should be described in sufficient detail to ensure the activity is performed consistently. 

The transfer of materials and equipment into classified areas presents a significant risk of contamination ingress into cleanrooms

It is also important to ensure that

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