Cleanroom are classified as "ISO Class 1'through to 'ISO Class 9'according to the international standard ISO 14644-1. An 'ISO Class 5'cleanroom,for example,is allowed a maximum concentration of 100,000 particles not larger than 0.1um in diameter within the cleanroom (particles/m3 of air). The table below shows the selected airborne particulate cleanliness classes for cleanrooms and clean zones;
ISO 14644-1 Cleanroom Standards: | ISO Classification Number | Maximum concentration limits(particles/m3 of air)for particles equal to and larger than the considered sizes shown below |
| 0.1μm | 0.2μm
| 0.3μm | 0.5μm | 1μm | 5μm | | ISO 1 | 10 | 2 |
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| | ISO 2 | 100 | 24 | 10 | 4 |
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| | ISO 3 | 1,000 | 237 | 102 | 35 | 8 |
| | ISO 4 | 10,000 | 2,370 | 1,020 | 352 | 83 |
| | ISO 5 | 100,000 | 23,700 | 10,020 | 3,520 | 832 | 29 | | ISO 6 | 1,000,000 | 237,000 | 102,000 | 35,200 | 8,320 | 293 | | ISO 7 |
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| 352,000 | 83,200 | 2,930 | | ISO 8 |
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| 3,520,000 | 832,000 | 29,300 | | ISO 9 |
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| 35,200,000 | 8,320,000 | 293,000 |
This table shows a comparison of the various classes that are used internationally;
Cleanroom Class Comparision: | ISO Classification Number | US FED 209E | BS 5295 | cGMP(operational) | | ISO 1 |
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| | ISO 2 |
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| | ISO 3 | M1.5(1) | 'C' |
| | ISO 4 | M2.5(10) | 'D' |
| | ISO 5 | M3.5(100) | 'E'or 'F' | A(B*) | | ISO 6 | M4.5(1,000) | 'G' or 'H' |
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