Dynamic vs. Static State Testing: Are We Measuring the Right Thing?

Cleanrooms are supposed to be predictable places — controlled, consistent, and compliant. Yet, when it comes to how we test them, there’s a global split in philosophy.

In one corner, we have ISO 14644-1:2015, focused on system capability under idealized, static conditions. In the other, the EU GMP and NAPRA approach — emphasizing dynamic testing to prove the room actually performs when people and processes enter the picture.

So, who’s right? And more importantly… are we measuring the right thing?

Let’s unpack the science, the standards, and a bit of the humor that lives between them.

1. Static vs. Dynamic — What’s the Difference, Really?

In simple terms, static (or “at-rest”) testing checks how the environment performs with equipment running but no people present. Dynamic (or “operational”) testing measures performance during actual use — when personnel, processes, and materials are in motion.

Think of it like checking your car’s fuel efficiency:

• Static testing measures it while idling in your driveway.

• Dynamic testing measures it while driving through downtown traffic with the A/C blasting.

One gives you a baseline; the other gives you reality.

2. ISO 14644-1:2015 — The Analytical Approach

ISO 14644-1:2015 defines how to classify air cleanliness by particle concentration. It clearly distinguishes three environmental states:

• As-built – Cleanroom is complete, utilities on, but no equipment or personnel.

• At-rest – Equipment installed and running, but no personnel.

• Operational (dynamic) – Equipment operating with personnel performing normal work.

  
  

ISO doesn’t mandate which state to use; it leaves it up to you, provided you can justify it. Most facilities choose “at-rest” testing because it isolates the room’s performance without the unpredictable influence of humans.

The ISO philosophy is:

“Prove the cleanroom can be clean.”

It’s a design validation mindset — confirming capability, not necessarily ongoing operational performance.

3. EU GMP — The Realist’s Approach

Meanwhile, EU GMP Annex 1 says, “That’s cute, but let’s see how it behaves when life happens.”

EU GMP places heavy emphasis on dynamic state testing, especially for aseptic processing environments. The reasoning is straightforward: Contamination risk isn’t theoretical — it’s human.

Personnel movement, door openings, equipment heat, and turbulence from process airflow all change the game. If your cleanroom only meets classification standards when it’s empty, you’re not measuring control — you’re measuring potential.

In short:

ISO validates the cleanroom’s design. EU GMP validates the cleanroom’s reality.

4. NAPRA — Canada’s Hybrid Model

Enter NAPRA (National Association of Pharmacy Regulatory Authorities), the governing body for sterile compounding in Canada.

NAPRA pulls from both ISO and EU GMP, merging analytical precision with operational realism.

It requires:

• Certification “at-rest” after installation or modification.

• Certification “operational” (dynamic) for routine requalification.

  
  

Why? Because in compounding pharmacies, the operator is the process. A room or BSC that passes perfectly while empty may fail miserably when someone starts compounding.

So while ISO says, “Test at-rest unless otherwise justified,” NAPRA says, “Test dynamically unless you can justify not doing so.”

That’s a critical inversion — and it’s reshaping how testing companies approach routine certification.

5. What Happens When You Test Dynamically

Dynamic testing isn’t just running the same tests with people in the room. It’s about understanding the interaction between process, personnel, and environment.

For example:

• Non-viable particle counts rise sharply when gowned personnel enter — but the question isn’t “how high,” it’s “does it stabilize quickly?”

• Smoke studies may reveal recirculation zones created by people, carts, or equipment.

• Pressure cascades can fluctuate with frequent door openings, showing weaknesses in air balance.

Dynamic testing forces you to observe the room under stress — not at its best, but at its most realistic.

6. Borderline Results — Interpreting the “Almost Fail”

Borderline results are where true expertise comes in.

A dynamic test may produce particle counts slightly over the limit, prompting panic. But context is key:

• Was it during setup or steady-state compounding?

• Was it one location or a trend across zones?

• Were activities typical, or were they stress tests?

Dynamic failures don’t always mean your room is broken. They often mean your process or behavior is the variable — and that’s exactly what dynamic testing is designed to reveal.

As one seasoned certifier likes to say:

“It’s not a failure — it’s a feedback loop.”

7. Risk-Based Scheduling and Justification

Testing frequency and method should be driven by risk, not routine.

• High-risk operations (aseptic filling, cytotoxic compounding) warrant regular dynamic requalification.

• Low-risk areas may only need static verification after major changes.

  
  

A sound justification ties test type and frequency to contamination risk, product sensitivity, and operational complexity — not just calendar months.

In other words, don’t test dynamically because it’s November; test dynamically because that’s when you’ll learn something useful.

8. Putting It All Together

Standard	Testing Focus	Typical State	Purpose
ISO 14644-1:2015	System capability	At-rest	Design verification
EU GMP Annex 1	Real-world performance	Dynamic	Operational qualification
NAPRA	Pharmacy compounding safety	Dynamic (routine)	Operator/process verification

So, to answer the question — are we measuring the right thing? That depends on what you’re trying to prove:

• Measure at-rest to validate design.

• Measure dynamic to validate safety.

• Measure both to truly understand your cleanroom.

  
  

9. A Final Thought — and a Little Humor

Cleanrooms are funny places. They’re the only rooms where perfection is demanded but rarely possible — and yet, that’s the whole point.

If ISO is the science of how air should behave, and EU GMP is the art of how people actually behave, then our job as testers is to bridge the two.

So next time someone says, “It passed at-rest, so we’re good,” you might reply:

“Sure — as long as you promise never to turn it on, touch anything, or breathe.”