Cleanroom Qualification and Acceptance - How Does It Work?
Qualification proves that a cleanroom reliably meets its agreed ISO class. This guide explains the four core acceptance tests to ISO 14644-3: airflow measurement, filter leak testing, particle classification to ISO 14644-1 and the recovery test.
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What Does Cleanroom Qualification Mean?
Qualification is the documented proof that a cleanroom actually reaches and holds its required air cleanliness class. Classification follows ISO 14644‑1 via particle concentration, while the test methods are defined in ISO 14644‑3.
Measurements are taken in three occupancy states: as built (finished, no equipment), at rest (equipment running, no staff) and in operation (equipment running, staff working). The state must always appear in the report, because the particle load depends heavily on it.
How Are Airflow and Filter Integrity Tested?
Two tests secure the foundation: airflow measurement determines volume flow and air change rate, while the leak test proves the integrity of the final filters (HEPA/ULPA). Both belong to every acceptance under ISO 14644‑3.
Airflow is measured directly at the filter outlet with a vane anemometer or a capture hood (balometer). Volume flow and room volume give the air change rate; for turbulent mixed ventilation, 20 to over 600 changes per hour are common depending on the class.
For the leak test a DEHS challenge aerosol is injected upstream and the filter face is scanned in overlapping strokes with a photometer or particle counter. Local penetration above 0.01 percent counts as a leak in the medium, frame or gasket and must be sealed.
How Is the Particle Class Determined?
Classification to ISO 14644‑1 measures the concentration of airborne particles with a calibrated particle counter. The ISO class results from the permitted limit per particle size and cubic metre of air.
- Number of sample points = square root of the room area in m², rounded up.
- Sample at working height with an isokinetic counter inlet.
- Choose a minimum sample volume that could capture at least 20 particles.
- ISO 5 allows 3,520 particles ≥ 0.5 µm per m³, ISO 7 already 352,000.
- Document each sample point and the overall average.
What Is the Recovery Test For?
The recovery test measures how quickly the cleanroom regains its cleanliness after a disturbance. It proves that ventilation and filters flush out a particle spike reliably - crucial for turbulently ventilated rooms of ISO 6 and above.
The particle concentration is deliberately raised by roughly 100 times, then the time to fall back to one hundredth is measured (100:1 recovery). A guideline value is under 20 minutes; the actual target is agreed between operator and tester.
Frequently asked questions
Which standard governs the test methods?
Classification follows ISO 14644‑1, while the acceptance test and measurement methods are described in ISO 14644‑3. The two are usually applied together.
How often must a cleanroom be requalified?
Every 6 to 24 months depending on class and application. Critical rooms of ISO 5 and above are tested more often, with particle measurement frequently every six months.
What is the 100:1 recovery time?
The time for an artificially raised particle concentration to fall back to one hundredth. It shows how fast the ventilation flushes out contamination, with a guideline under 20 minutes.
How many sample points are needed?
The minimum equals the rounded-up square root of the room area in square metres. A 25 m² room therefore needs five sample points.
Need your cleanroom qualified?
We supply particle counters, capture hoods and challenge aerosols for acceptance to ISO 14644-3 - including calibrated instruments.
Standard-compliant
Tests to ISO 14644-1 and 14644-3.
Calibrated
Particle counters and hoods with certificates.
Documented
Complete qualification report per room.
Expert advice
Cleanroom specialists support the acceptance.