Minimising damage from sterilisation routines

Increasingly rigorous sterilisation routines and far higher concentrations of disinfectant are being normalised across many industries, so Sue Springett from Teknomek says considerations must be taken for future proofing furniture against reduced life

Rusting on equipment from a sterilisation routine

Former US Vice President Donald Rumsfeld brought the concepts of 'known knowns' 'unknown knowns' and 'unknown unknowns' into popular parlance within the business world. One of the greatest challenges in the design and build of a new facility is, by its nature, planning for what you don't yet know.

We can factor in our known knowns - business growth plans and technology decisions. But it's worth also considering how hygiene requirements may evolve - an unknown unknown. But how unknown are these really?

We can extrapolate on recent trends to make some informed predictions. For instance, there's been a move towards increasingly rigorous sterilisation routines and far higher concentrations of disinfectant used within cleanrooms over the past half-decade. This suggests we can safely expect this to have a longer-term impact when specifying a new cleanroom, and that should therefore inform design choices.

If we step back to review the changes over the last few years, we've also seen an increasing use of swab tests to monitor the stability of microbe counts. While we can't be exactly sure what happens next in terms of specifying for future risk, these developments demonstrate that GMP management doesn't stand still - that's a known unknown. So it can be factored in. Consequently, we know the planning phase for microbial risk management deserves extra attention.

Knowledge is power

A case in point is furniture design. Microbes aren't only present on the surfaces you can see, so look for designs that remove harbourage points - from every angle. It's sensible to refer back to microbial alerts in previously installed furniture when assessing risk in new models. Any form factors that have demonstrably required additional cleaning or management should be avoided for the future.

The use of higher strength disinfectants could reduce the lifespan of that furniture and support equipment, it could be further impaired if the frequency of cleaning/sterilising routines continue to rise.

While the stainless steel grade is the primary consideration

So, if you're aware of a move away from IPA wipes and disinfectant and towards the use of autoclaves or atomised or vaporised hydrogen peroxide within your business, it's prudent to factor this into furniture choices.

In our experience, the numbers of new builds opting for bespoke 316 grade installations have grown by around one third over the past three years. The reasoning is sound, the chemical make-up of this grade of stainless steel includes added molybdenum. This makes it more resistant to corrosion and is thus better suited to hydrogen peroxide and oxidisation than the pharma-standard 304 grade, and delivers a longer product life.

Build for now, plan for later

While the stainless steel grade is the primary consideration during specification, there are other factors at play. Most notably, the Ra count. This dictates how coarse the surface finish is; the rougher the surface, the greater the risk that harsh chemicals will "pool" and cause surface corrosion.

The highly concentrated disinfectants that are becoming increasingly normalised in the sector must be thoroughly wiped away to prevent rouging - a form of corrosion that destroys the passive layer of stainless steel. Even trace amounts of disinfectant can hasten the demise of the stainless steel if - for example - they are not entirely cleared from micropores.

While the compliance standard set by ISO 14644 for cleanroom Class 5 is currently 0.6 Ra, it is worth viewing this as a bare minimum for the longer term. A lower Ra count means the steel is less vulnerable to damage from the stronger chemicals that may be used going forward.

So, when designing a cleanroom, it makes sense to not only build for now, but to plan for the future. It will need to withstand whatever is thrown at it.

Even though you might not be using especially harsh cleaning and sterilisation options in the short-term, there's nothing to say that won't change. Certainly, new build trends would suggest that 316-grade stainless steel could well become the default for aseptic production, this points to tougher becoming the norm. Equally, there's nothing to say that regulatory standards will always remain the same in light of growing understanding of hygiene management of offensive toxins.

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Making the grade

If you are absolutely sure that the long-term use case for the cleanroom will not change and you won't have to upgrade your cleaning and/or sterilisation routines, then 304-grade stainless steel remains a safe option. It has been the most favoured material across the pharma sector for decades - and with good reason. Over-specifying can be almost as wasteful as under-specifying if you really don't, or won't, need the added protection.

Designs will need to withstand whatever is thrown at it

That said, if there is any chance you may need to pivot, then electropolished 316-grade or TRESPA TopLab surfaces are viable alternatives. Both offer very similar chemical resistance, durability and antimicrobial properties, and a an even lower Ra count. These factors make them capable of withstanding even the most demanding of disinfectants and sterilisation methods.

Each provides benefits for particular use cases: stainless steel remains the most practical material given it can be re-passivated if it is damaged, whereas TRESPA work tops need to be permanently retired from hygiene-controlled areas if they are chipped.

Microbes aren’t only present on the surfaces you can see

If aesthetics are also an important consideration, then TRESPA deserves attention. Electropolishing gives stainless steel a reflective sheen that may not be to everyone's taste as their highly reflective properties cause glare in well-lit environments. TRESPA, by comparison, is available in different matte finishes to suit staff welfare.

Life time value calculations

As we've all learnt from the corona pandemic, we live in a dynamic and ever-changing world that frequently presents new challenges. Despite the unknown unknowns, the one consideration that you cannot afford to lose sight of is the TCO over the cleanroom's lifetime. Making the wrong choices, whether that's down to over or under-specifying, can mean you end up paying far more than planned for, or indeed needed to. This becomes particularly acute if you end up having to replace and refit - and any downtime that may result.

Best practice during build specification is to work backwards from the practicalities of the day to day as it stands now, but with half an eye to the future - taking into account the known knowns, known unknowns and unknown unknowns. So perhaps the key takeaway should be that it often pays to build in flexibility. Playing it safe may be frowned upon in most business, but cleanrooms are the exception to the rule. And that's a fact.

N.B. This article is featured in the September 2020 issue of Cleanroom Technology. Subscribe today and get your print copy!

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