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EU Guidelines to Good Manufacturing Practice: Annex 1
maximum particles/m³ 14644-1:2015 maximum particles/m³ 14644-1:2015
equivalent equivalent
Grade At Rest Grade In Operation
≥0.5μm ≥5.0μm ISO ≥0.5μm ≥5.0μm ISO
A 3,520 20 5 (4.8) A 3,520 20 5 (4.8)
B 3,520 29 5 B 352,000 2,900 7
C 352,000 2,900 7 C 3,520,000 29,000 8
D 3,520,000 29,000 8

* Note: Particle classifications are not exactly per ISO 14644-1:1999; differences are noted in bold.