| ISO |
FED STD 209 |
0.1 Microns |
0.2 Microns |
0.3 Microns |
0.5 Microns |
5.0 Microns |
| Class 3 |
1 |
1000/35 |
|
|
35/1 |
|
| Class 4 |
10 |
10,000/345 |
75 |
30 |
352/10 |
0 |
| Class 5 |
100 |
100,000/3,450 |
750 |
300 |
3520/100 |
0 |
| Class 6 |
1,000 |
1,000,000/34,500 |
N/A |
N/A |
35,200/1,000 |
7 |
| Class 7 |
10,000 |
345,000 |
N/A |
N/A |
352,000/10,000 |
70 |
| Class 8 |
100,000 |
3,450,000 |
N/A |
N/A |
3,520,000/100,000 |
700 |
ISO 14644-1 (per cubic meter)
Fed Std. 209 E USA (per cubic foot)
ISO standard requires results to be shown in cubic meters (1 cubic meter = 35.314 cubic feet)
Class 1
540 to 600+ air changes per hour (98%+ ceiling coverage)
ULPA filters (99.9995% on .12 microns)
Gel/Flush grid ceiling systems with raised floors are required
Outside/makeup air to be prefiltered with a HEPA filter
Class 10
540 to 600 air changes per hour (85-90% ceiling coverage)
99.999% on 0.3 microns, with a raised floors
90%+ coverage with low wall returns
Gasketed grids with negative plenums acceptable
HEPA filters on makeup air
Class 100
400 to 480 air changes per hour (60-80% ceiling coverage)
99.99% HEPA filters
Raised floor assures optimal performance. Low wall returns work when they are no further than 12' from the center of the roomı
Gasketed ceiling grid
Class 1,000
120 to 150 air changes per hour (40-50% ceiling coverage)
99.99% HEPA filter
Gasketed ceiling grid
Raised floor delivers best performance, but low wall returns are very commonı
Class 10,000
45 to 60 air changes per hour (10-20% ceiling coverage)
99.97% or 99.99% HEPAs
Low wall or ceiling returns acceptable in most applicationsı
Class 100,000
20 to 30 air changes per hour (5% ceiling coverage)
HEPA filters or 95% HEPAs (95%+ ASHRAE box filters²) located downstream of the HVAC unit
Heat load may require more air changes
1. Room layout with equipment must be evaluated to look for return air paths and possible cross contamination.
2. 95% ASHRAE filters when new may only be 70% and could affect the particle level.
Important point to consider concerning filter coverage.
A 300 sq. ft. cleanroom may need 90% coverage (38 HEPAs) for Class 100 at the "operational" mode, 60% coverage (23) in the "at rest" mode, and only 40% (15) to meet Class 100 at "as built". The same rules can and do apply to Class 1,000 and Class 10,000 levels.
