The degree of purity of the room’s air determines its purity class

Each cleanroom is assigned a purity class, which defines the maximum permissible particle concentration in the cleanroom air. The purity class is one of the most important criteria when selecting the optimal cleanroom garments system.

Not all cleanrooms are the same. One of the most important differentiators is the particle concentration permissible for the respective industry and production. This is gauged by the particle concentration of the room’s air and categorised into different purity classes. Accordingly, the cleanrooms or clean working areas are evaluated and assigned specific purity classes. Different measuring methods and threshold values are used to determine the maximum permissible particle concentration per m³.

The most important applicable standards are those supplied in the EU GMP guidelines (Annex 1) as well as in DIN EN ISO 14644-1.

Categorisation of purity class according to the EU GMP guidelines, Annex 1

Class Non-operational Operational
≥ 0.5 µm ≥ 5.0 µm ≥ 0.5 µm ≥ 5.0 µm
A 3,520 20 3,520 20
B 3,520 29 352,000 2,900
C 352,000 2,900 3,520,000 29,000
D 3,520,000 29,000 * *
*) Not specified

Categorisation of purity class according to EN ISO 14644-1

Maximum number of particles per m³

Class Size
≥ 0.1 µm ≥ 0.2 µm ≥ 0.3 µm ≥ 0.5 µm ≥ 1.0 µm ≥ 5.0 µm
ISO 1 10 2
ISO 2 100 24 10 4
ISO 3 1,000 237 102 35 8
ISO 4 10,000 2,370 1,020 352 83
ISO 5 100,000 23,700 10,200 3,520 832 29
ISO 6 1,000,000 237,000 102,000 35,200 8,320 293
ISO 7 352,000 832,000 2,930
ISO 8 3,520,000 832,000 29,300
ISO 9 35,200,000 8,320,000 293,000
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