ISO 14644-1 Classification of Air Cleanliness by Particle Concentration


The ISO 14644-1 standard  applies to a variety of industries, including healthcare, pharmaceuticals, food production, medical device and aerospace manufacturing. This international standard defines classes of air cleanliness for cleanrooms and controlled environments relative to the number, or concentration, of particles in air volume. A particulate testing method is required in combination with a calculated selection of sampling locations.


Part 1 addresses the guidelines, specifications and rules for cleanroom certification in relation to airborne particle concentration (cumulative distributions based sizes ranging from 0.1 µm to 5 µm). 

More Recent Modifications Include—

  • Exclusion of particles > 5 microns from the ISO Class 5 classification table - ISO Class 5 at ≥5 microns equivalent to GMP Grade B at rest
  • More consistent approach for selection and number of sample points, including evaluation of data collected
  • Each location to be treated independently
  • Elimination of 95% Upper Confidence Limits (UCL) for low sample location numbers (2-9)
  • All light scattering airborne particle counters to be calibrated to ISO 21501-4  

ISO 14644-2 Monitoring and Testing

Among new considerations including monitoring critical parameters and setting action and alert alarms, ISO 14644-2 now allows companies to use risk management protocols to establish a periodic classification testing schedule. Prescribed testing has been replaced with increased emphasis on day-to-day onsite data, which is used to determine appropriate testing and frequency required to maintain compliance.

ISO 14644-1 Air Classifications

 Clean Area Classification (0.5 um particles/ft3) ISO Designation**   >0.5 µm particles/m3 Microbiological Active Air Action Levels*** (cfu/m3)  Microbiological Settling Plates Action Levels (diam. 90 mm; cfu/4 hours) 
100   5  3,520  1∞  1∞
 1,000  6  35,200  7  3
 10,000  7  352,000  10  5
 100,000  8  3,520,000  100  50

*Classifications based on data measured in the vicinity of exposed materials/articles during periods of activity; as defined in USA cGMP. 
ISO 14644-1 designations provide uniform particle concentration values for cleanrooms in multiple industries. An ISO 5 particle concentration is equal to Class 100 and approximately equals EU Grade A.
**Values represent recommended levels of environmental quality. Cleanroom operators may find it appropriate to establish alternate microbiological action levels due to the nature of the operation or method of analysis. 
***Additional use of settling plates is optional. 
∞Samples from Class 100 (ISO 5) environments should typically yield no microbiological contaminants. 

SOURCE: Air Classifications Table: Guidance for Industry Sterile Drug Products Produced by Aseptic Processing - Current Good Manufacturing Practice (US)

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