Electronics ManufacturingFree referencePDF, Excel, Word exportSemiconductors

ISO 14644-1 Cleanroom Particle Concentration Limits (Class 1 to 9)

This table lists maximum airborne particle concentrations per cubic metre for each ISO 14644-1 cleanroom class at the standard particle sizes, with the old Federal Standard 209E names beside them. It answers the common questions: what is ISO 5 equal to, and how many 0.5 um particles are allowed in ISO 7.

Download:
ISO class0.1 um0.2 um0.3 um0.5 um1 um5 umFed Std 209E approx.
ISO 1
10
2
n/a
n/a
n/a
n/a
n/a
ISO 2
100
24
10
4
n/a
n/a
n/a
ISO 3
1,000
237
102
35
8
n/a
Class 1
ISO 4
10,000
2,370
1,020
352
83
n/a
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 1,000
ISO 7
n/a
n/a
n/a
352,000
83,200
2,930
Class 10,000
ISO 8
n/a
n/a
n/a
3,520,000
832,000
29,300
Class 100,000
ISO 9
n/a
n/a
n/a
35,200,000
8,320,000
293,000
n/a

Values are maximum permitted concentrations in particles per cubic metre of air, as commonly tabulated from ISO 14644-1 (2015 edition). Fed Std 209E was withdrawn in 2001 but its class names are still widely used. n/a means the class is not defined at that size. Confirm limits against the current licensed standard before using them in a procedure or audit response.

Environmental monitoring trend review

Optional: ideas for turning particle count logs into trend and excursion queries.

Optional. The tool and every export work without this. No spam.

How to use the table

Find your ISO class in the first column and read across for the particle size you monitor. Most semiconductor fabs count at 0.1 um or 0.5 um depending on the class, and OSATs commonly monitor 0.5 um and 5 um. Use the Fed Std column to translate older drawings and customer requirements into ISO classes.

  • Compare your particle counter readings with the limit at the same size
  • Remember that limits are per cubic metre, counters often report per cubic foot
  • Note n/a entries are undefined, not zero

How the classes are built

The classification follows a formula where the limit for each size scales with the class number. Each step in ISO class changes the allowed concentration by a factor of ten, and the limit falls steeply as particles get larger. That is why an ISO 5 area allows 3,520 particles of 0.5 um per cubic metre while ISO 7 allows 352,000.

Worked example: unit conversion

A counter reports 85 particles per cubic foot at 0.5 um. One cubic metre is about 35.31 cubic feet, so that is roughly 3,000 particles per cubic metre. This is under the ISO 5 limit of 3,520 for that size. Class determination also needs the sampling plan and statistics from the standard, not a single reading.

Common mistakes

Classification is not the same as routine monitoring, and the standard separates the two. Do not compare at-rest results to in-operation limits without stating the occupancy state. Do not cite Fed Std class names in a new specification when an ISO class is available, and always record the sampling location count and volume per location.

Frequently Asked Questions

What ISO class is equal to Class 100?

Federal Standard 209E Class 100 corresponds approximately to ISO 5 in ISO 14644-1. The 209E standard was withdrawn in 2001, but the class names remain in common use.

How many 0.5 um particles are allowed in ISO 7?

The limit is 352,000 particles per cubic metre at 0.5 um. ISO 7 corresponds approximately to Fed Std Class 10,000.

Why are some table cells n/a?

The standard does not define a limit for those size and class combinations, because very small particles are not practical to count at high concentration classes. Use the sizes defined for your class.

Does this table replace the standard?

No. It is a convenient reference. Classification and monitoring procedures, sampling locations and statistics are specified in the standard itself, which you should obtain through a licensed source.

If your environmental monitoring data sits in spreadsheets or a LIMS, Netray can help build trend queries and alerts on your own infrastructure.

Talk to an ExpertExplore More Free Tools

Related Tools

Electronics Manufacturing

Semiconductor Process Tool Qualification Checklist

Checklist covering facilities hookup, safety, hardware acceptance, process qualification and production release for a fab or OSAT tool.

Electronics Manufacturing

Semiconductor Wafer Size and Thickness Reference

Lookup table of standard silicon wafer diameters, nominal thicknesses, areas and typical applications.

Developer Tools

Western Electric Rules SPC Python Script Generator

Creates a standalone Python script that reads a CSV column and flags points breaking the four Western Electric run rules.

Electronics Manufacturing

Semiconductor Package Types Reference

Lookup table of common IC package families with full names, terminal style, interconnect method and typical applications.

More Electronics Manufacturing tools

See all
Back to All Tools