Cleanroom Classification Tables

Discover the different classes within the cleanroom ISO standards and their Federal Standard and GMP equivalent. These tables detail the particle counts that define each class. 

ISO 14644-1:2015 Cleanroom Classification

ISO 14644 is the international standard for cleanrooms and associated controlled environments. Part 1 details the classification of air cleanliness by particle concentration. 

This table details the air cleanliness classes by particle concentration within ISO 14644-1.
ISO Classification NumberMaximum allowable concentrations (particles/m3) for particles equal to and greater than the considered sizes, shown below
≥0.1µm ≥0.2µm ≥0.3µm ≥0.5µm ≥1µm ≥5.0µm
ISO Class 1 10b d d d d e
ISO Class 2 100 24b 10b d d e
ISO Class 3 1,000 237 102 35b d e
ISO Class 4 10,000 2,370 1,020 352 83b e
ISO Class 5 100,000 23,700 10,200 3,520 832 d,e,f
ISO Class 6 1,000,000 237,000 102,000 35,200 8,320 293
ISO Class 7 c c c 352,000 83,200 2,930
ISO Class 8 c c c 3,520,000 832,000 29,300
ISO Class 9g c c c 35,200,000 8,320,000 293,000

a All concentrations in the table are cumulative, e.g. for ISO Class 5, the 10,200 particles shown at 0.3µm include all particles equal to and greater than this size. 
b These concentrations will lead to air sample volumes for classification. Sequential sampling procedure may be applied.
c Concentration limits are not applicable in this region of the table due to very high particle concentration.
d Sampling and statistical limitations for particles in low concentrations make classification inappropriate.
e Sample collection limitations for both particles in low concentrations and sizes greater than 1µm make classification at this particle size inappropriate, due to potential losses in the sampling system.
f In order to specify at this particle size in association with ISO Class 5, the macroparticle descriptor M may be adapted and used in conjunction with at least one other particle size.
g This class is only applicable for the in-operation state.

Maximum permitted total particle concentration for classification by GMP grade

GMP Annex 1 details the maximum permitted particle concentrations for classification, for 'at rest' and 'in operation' states. 

Clean room and clean air device classification, in relation to GMP Annex 1 (2015).
GradeMaximum limits for total particle ≥0.5µm/m³Maximum limits for total particle ≥5.0µm/m³
At rest In operation At rest In operation
A 3,520 3,520 Not specifieda Not specifieda
B 3,520 352,000 Not specifieda 2,930
C 352,000 3,520,000 2,930 29,300
D 3,520,000 Not predeterminedb 29,300 Not predeterminedb

a Classification including 5µm particles may be considered where indicated by the CCS or historical trends.
b For grade D, in operation limits are not predetermined. The manufacturer should establish in operation limits based on a risk assessment and routine data where applicable.

Comparison of Cleanroom Classifications

The 'at rest' limits for GMP, correspond with the limits for ISO classes. 

This table below shows the ISO classes with the equivalent GMP grades. It also details the equivalent Federal Standard class.
Cleanroom StandardCleanroom Classification Guidelines
ISO 14644-1 Class 3 Class 4 Class 5 Class 6 Class 7 Class 8
EU GMP (at rest) - - A/B - C D
Federal Standard 209E (replaced in 2001) 1 -10 100 1,000 10,000 100,000

The Federal Standard class was replaced by ISO 14644 in 2001.


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