Contamination Control by Design: 6 Decisions Made Too Late

Most contamination problems are not caused by the moment they appear. They are caused by a decision taken months or years earlier, when the facility was on a drawing rather than on the floor. Contamination control by design is the discipline of making those decisions on purpose, and at the point where they are still cheap to make. The alternative is to inherit them, and then spend the life of the facility managing around them.

Contamination control by design: decide early, do not manage late

The pattern repeats across sterile and non-sterile projects. Six decisions in particular tend to be deferred, made by default, or made by someone optimising for cost or schedule rather than contamination risk. Each one is inexpensive to get right on paper and expensive to fix once concrete is poured or a line is installed. This piece sets out the six, in roughly the order they arise, and what it costs to leave each one too late.

1. Facility layout and flow

The movement of people, materials, and waste through a facility is fixed early, because it drives the position of walls, airlocks, and pressure cascades. When flow is treated as something to resolve during detailed design, the result is crossovers that no procedure can fully remove. Personnel and material flows that intersect, or a pressure regime that fights the intended flow, become permanent constraints. Deciding flow first, against the contamination risk of the process, is the foundation that the rest of contamination control by design rests on.

2. Cleanroom classification and adjacencies

Which grade sits next to which is a design decision, not an operational one. A high-grade zone opening onto a lower-grade corridor without a properly designed transition is a risk that gets built into the walls. When classification and room adjacencies are settled late, sites end up adding gowning steps, interlocks, and monitoring to compensate for an arrangement that should have been avoided. The contamination control burden then falls on procedures for the life of the facility.

3. Barrier technology: RABS or isolator

The choice between a restricted access barrier system and an isolator shapes almost everything downstream: room grade, air handling, cleaning, and the way operators interact with the process. Made early, it is a design input. Made late, after the line and room are largely fixed, it becomes a compromise. Retrofitting a barrier into a space that was not planned for it drives cost and rarely delivers the contamination control that choosing it at concept stage would have. The barrier technology decision belongs at the start, not after the layout is frozen.

4. Air handling and recovery

Air change rates, recovery times, and pressure stability are set by the HVAC design, and that design is sized against assumptions about grade, occupancy, and equipment heat load. When those assumptions are optimistic, or when the system is value-engineered late to save capital cost, the facility struggles to hold its classification under real operating conditions. Recovery time after an intervention is a good example: it is easy to specify and hard to fix once the plant is installed and undersized.

5. Cleanability and equipment design

Surfaces, finishes, drainage, and equipment geometry decide whether a facility can actually be cleaned to the standard its grade implies. Dead legs, poor drainability, crevices, and materials that degrade under repeated cleaning are all decided during design and procurement. Once installed, they become recurring environmental monitoring excursions and cleaning validation headaches. Designing for cleanability means asking, before purchase, how each surface and each piece of equipment will be cleaned and how that will be demonstrated.

6. The monitoring and control strategy itself

Environmental monitoring and the wider contamination control strategy are often written after the facility is built, which reverses the intended order. A contamination control strategy is meant to be the logic that drives design decisions, not a document assembled to describe a facility that already exists. When it is left to the end, monitoring locations are chosen to fit the room rather than the risk, and the strategy documents the facility's limitations instead of controlling them. Building the strategy first, as contamination control by design intends, is what makes the other five decisions coherent.

Why too late is so expensive

The common thread is that each of these decisions moves from cheap to expensive at a predictable point: when it stops being a line on a drawing and becomes a physical constraint. Fixing a flow problem in design is a revision. Fixing it after construction is a capital project. Sites that treat contamination control as a design input rather than an operational cleanup avoid a class of cost that never appears on the original budget but shows up for the life of the facility. Where a facility is already built and carrying these decisions, structured GMP remediation prioritises the ones that carry the most contamination risk.

Frequently asked questions

What is contamination control by design?

Contamination control by design is the practice of making contamination control decisions at the design stage, where they are deliberate and inexpensive, rather than managing around them once the facility is built. It treats layout, grade, barrier choice, air handling, cleanability, and the control strategy as design inputs.

Why are these decisions made too late?

They are often deferred because they compete with cost and schedule pressure, or because the contamination control strategy is written after the facility exists rather than before. Once concrete is poured or a line is installed, a cheap design revision becomes an expensive physical change.

Which decision matters most?

Facility layout and flow, because it fixes the position of walls, airlocks, and pressure cascades that everything else depends on. A flow problem built into the structure cannot be fully removed by procedures later.

Can contamination control by design help an existing facility?

Yes. An existing site cannot un-build its early decisions, but the same logic identifies which inherited decisions carry the most risk, so remediation effort goes where it reduces contamination risk the most rather than being spread evenly.

Kieran Falvey is Founder and Managing Director of Pharmalliance Consulting Ltd and the creator of Contamination Control by Design (CCbD). He has more than 20 years designing, building and running pharmaceutical facilities worldwide, across FDA, EMA, TGA, PIC/S and Indian FDA (CDSCO) jurisdictions. Global expert in cGMP Compliance, Remediation and Contamination Control, helping Sterile, Non-Sterile, ATMP and Cosmetic companies navigate cGMP compliance issues.

Pharmalliance Consulting is a GMP compliance consultancy serving pharmaceutical, sterile, non-sterile, OSD, ATMP and cosmetic manufacturers in Ireland, the UK, the EU and the US. It helps sites identify and remediate GMP risks across facilities, quality systems and contamination control, aligned with HPRA, MHRA, EMA and FDA expectations, turning findings into defensible, inspection-ready practice.

If you are planning a facility or a line, the cheapest time to fix these six decisions is now, before they are built in. Talk to Pharmalliance about Contamination Control by Design or contact the team.