CEILING FILTER COVERAGE
Air Changes and Ceiling Filter Coverage
The table below combines ceiling coverage and air change rate guidelines by ISO class into a single reference. These figures represent widely accepted industry guidelines — actual requirements will vary based on your specific application, room configuration, airflow design, and the equipment and personnel present during operation. Work with one of our cleanroom design experts to determine the parameters appropriate for your project.
| ISO Class | Fed-Std 209E Class | Air Changes Per Hour | Ceiling Coverage |
|---|---|---|---|
| ISO 1 | — | 500–750 | 90–100% |
| ISO 2 | — | 500–750 | 80–100% |
| ISO 3 | Class 1 | 500–750 | 60–100% |
| ISO 4 | Class 10 | 400–750 | 50–90% |
| ISO 5 | Class 100 | 240–600 | 35–70% |
| ISO 6 | Class 1,000 | 150–240 | 25–40% |
| ISO 7 | Class 10,000 | 60–150 | 15–20% |
| ISO 8 | Class 100,000 | 6–60 | 5–15% |
Note: For ISO Classes 1–5, air change rates are sufficiently high that they are often expressed as airflow velocity (ft/min) rather than air changes per hour. See the Air Change Rates by ISO Class table on our Air Circulation in Cleanrooms page for velocity ranges.
ISO 14644-1 Cleanroom Standards
The table below shows the maximum allowable airborne particle concentrations by ISO class per ISO 14644-1. Particle counts are cumulative — values at a given particle size include all particles equal to or larger than that size.
| 209 E Standard | Class | Maximum Allowed Concentration (particles per m³)a | |||||
|---|---|---|---|---|---|---|---|
| ≥0.1 µm | ≥0.2 µm | ≥0.3 µm | ≥0.5 µm | ≥1 µm | ≥5 µm | ||
| ISO 1 | 10b | d | d | d | d | e | |
| ISO 2 | 100 | 23.7b | 10.2b | d | d | e | |
| CLASS 1 | ISO 3 | 1,000 | 237 | 102 | 35b | d | e |
| CLASS 10 | ISO 4 | 10,000 | 2,370 | 1,020 | 352 | 83 | e |
| CLASS 100 | ISO 5 | 100,000 | 23,700 | 10,200 | 3,520 | 832 | d, e, f |
| CLASS 1,000 | ISO 6 | 1,000,000 | 237,000 | 102,000 | 35,200 | 8,320 | 293 |
| CLASS 10,000 | ISO 7 | c | c | c | 352,000 | 83,200 | 2,930 |
| CLASS 100,000 | ISO 8 | c | c | c | 3,520,000 | 832,000 | 29,300 |
| ISO 9 | 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.
f In order to specify 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.
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