US FED STD 209E was officially cancelled by the General Services Administration of the US Department of November 29, 2001 but is still widely used.
ISO 14644-1 Cleanroom Standards
Class
|
maximum particles/m³
|
FED STD 209E equivalent
|
≥=0.1 µm
|
≥=0.2 µm
|
≥=0.3 µm
|
≥=0.5 µm
|
≥=1 µm
|
≥=5 µm
|
ISO 1
|
10
|
2
|
|
|
|
|
|
ISO 2
|
100
|
24
|
10
|
4
|
|
|
|
ISO 3
|
1,000
|
237
|
102
|
35
|
8
|
|
Class 1
|
ISO 4
|
10,000
|
2,370
|
1,020
|
352
|
83
|
|
Class 10
|
ISO 5
|
100,000
|
23,700
|
10,200
|
3,520
|
832
|
29
|
Class 100
|
ISO 6
|
1,000,000
|
237,000
|
102,000
|
35,200
|
8,320
|
293
|
Class 1000
|
ISO 7
|
|
|
|
352,000
|
83,200
|
2,930
|
Class 10,000
|
ISO 8
|
|
|
|
3,520,000
|
832,000
|
29,300
|
Class 100,000
|
ISO 9
|
|
|
|
35,200,000
|
8,320,000
|
293,000
|
Room air
|
|