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How particles move in a cleanroom
Contamination doesn't just float. It settles, accumulates, and threatens your process.
Three complementary measurements, from airborne counts to surface inspection, reveal the full contamination story your cleanroom is telling.
In a cleanroom, particle contamination doesn't behave the same way everywhere, so a single measurement method is insufficient.
We distinguish three types of particle contamination, each requiring a different form of monitoring.
ISO 14644-1
Airborne particle counting
Looks at particles still suspended in the air, counting how many are floating within a cubic meter at any given moment. Expressed as particles per m³, it is the classic clean air metric. It tells you how contaminated the atmosphere itself is, before anything has settled.
ISO 14644-17, PDRL
Particle fallout monitoring
Tracks what happens next. Airborne particles eventually succumb to gravity and drift down onto the surfaces below. This method measures the deposition rate, how many particles land on a surface per m² per hour. It reflects the clean process risk, because particles falling out of the air are exactly what could contaminate an open product or process.
ISO 14644-9, SCP
Surface particle inspection
Looks at the end state, the particles that have already accumulated on a surface, regardless of when or how they got there. Measured as particles per m², it represents clean surfaces, a static snapshot of contamination on equipment, tools, or work surfaces rather than a rate.
The physical story is sequential. Particles exist in the air, some fall out and land on surfaces, and the surfaces accumulate a standing particle population.
A complete contamination-control picture therefore requires knowing not just how clean the air is, but also how fast it's depositing particles and how clean surfaces actually end up.
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