Class Limits

    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 room¹ 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 common¹

    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 applications¹

    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.

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Class Limits


Testing


USP797


Definitions


Annual Maintenance Contract.


1) AHUs, Cleanrooms, Laminar Flow work stations.
2) Largest inventory of air filters [20, 10, 5, 3 micron] pre filters and hepa filters.
3) Room differential pressure management.
4) Periodical testing & Validation of cleanrooms.