| Cleanliness Level | ISO | FED STD 209E Equivalent | Maximum Particles / Cubic Meter | |||||
| 0.1 Micron | 0.2 Micron | 0.3 Micron | 0.5 Micron | 1 Micron | 5 Microns | |||
| Extremely Clean | ISO 1 | N/A | 10 | 2 | N/A | N/A | N/A | N/A |
| ISO 2 | N/A | 100 | 24 | 10 | 4 | N/A | N/A | |
| ISO 3 | Class 1 | 1,000 | 237 | 102 | 35 | 8 | N/A | |
| ISO 4 | Class 10 | 10,000 | 2,370 | 1,020 | 352 | 83 | N/A | |
| ISO 5 | Class 100 | 100,000 | 23,700 | 10,200 | 3,520 | 832 | 29 | |
| ISO 6 | Class 1,000 | 1,000,000 | 237,000 | 102,000 | 35,200 | 8,320 | 293 | |
| ISO 7 | Class 10,000 | N/A | N/A | N/A | 352,000 | 83,200 | 2,930 | |
| ISO 8 | Class 100,000 | N/A | N/A | N/A | 3,520,000 | 832,000 | 29,300 | |
| Clean | ISO 9 | N/A | N/A | N/A | N/A | 35,200,000 | 8,320,000 | 293,000 |
