This section specifies the classification of air cleanliness in terms of concentration of airborne particles in cleanrooms and clean zones.
Only particle populations having cumulative distributions based on the threshold particle sizes ranging from 0.1 µm to 5.0 µm are considered for the classification purposes.
The use of light scattering (discrete) airborne particle counters (LSAPC) is the basis for determination of the concentration of airborne particles, equal to and greater than the specified sizes, at designated sampling locations.
Apex Z3 – 1 CFM Portable Airborne Particle Counter
An M descriptor (see Annex C) may be used to quantify populations of macroparticles (particles larger than 5.0 µm).
This part of ISO 14644 cannot be used to characterize the physical, chemical, radiological, viable or other nature of airborne particles.
How to determine the number of sample locations:
ISO14644-1:2015 New Maximum Concentration Limits
De-emphasis of the ≥ 5 µm ISO Class 5 limit