Cleanroom classifications

Cleanroom classifications

Cleanrooms are classified according to the number and size of particles permitted per volume
of air. Large numbers like "class 100" or "class 1000"
refer to FED-STD-209E, and denote
the number of particles of size 0.5 µm or larger permitted per cubic foot of
air. The standard also allows interpolation, so it is possible to describe e.g.
"class 2000".

A discrete-particle-counting, light-scattering instrument is used to determine
the concentration of airborne particles, equal to and larger than the specified
sizes, at designated sampling locations.

Small numbers refer to ISO 14644-1 standards, which specify the decimal logarithm of the number of particles 0.1 µm or larger
permitted per cubic metre of air. So, for example, an ISO class 5 cleanroom has at most 105 = 100,000 particles per m³.

Both FS 209Eand ISO 14644-1 assume log-log relationships between particle size and particle
concentration. For that reason, there is no such thing as zero particle
concentration. The table locations without entries are non-applicable
combinations of particle sizes and cleanliness classes, and should not be read
as zero.

Because 1 m³ isapproximately 35 ft³, the two standards are mostly equivalent when measuring 0.5 µm particles, although the testing standards differ. Ordinary room air isapproximately class 1,000,000 or ISO 9.

US FED STD 209E
cleanroom standards

Class

maximum particles/ft³

ISO

  equivalent

≥0.1 µm

≥0.2 µm

≥0.3 µm

≥0.5 µm

≥5 µm

1

35

7.5

3

1

0.007

ISO 3

10

350

75

30

10

0.07

ISO 4

100

3,500

750

300

100

0.7

ISO 5

1,000

35,000

7,500

3000

1,000

7

ISO 6

10,000

350,000

75,000

30,000

10,000

70

ISO 7

100,000

3.5×106

750,000

300,000

100,000

700

ISO 8

US FED STD 209E was officially cancelled by the General Services Administration of the US Department of Commerce November 29, 2001, but is still widely use

ISO 14644-1
cleanroom standards

Class

maximum particles/m³

FED STD 209E

  equivalent

≥0.1 µm

≥0.2 µm

≥0.3 µm

≥0.5 µm

≥1 µm

≥5 µm

ISO 1

10

2.37

1.02

0.35

0.083

0.0029

 

ISO 2

100

23.7

10.2

3.5

0.83

0.029

 

ISO 3

1,000

237

102

35

8.3

0.29

Class 1

ISO 4

10,000

2,370

1,020

352

83

2.9

Class 10

ISO 5

100,000

23,700

10,200

3,520

832

29

Class 100

ISO 6

1.0×106

237,000

102,000

35,200

8,320

293

Class 1,000

ISO 7

1.0×107

2.37×106

1,020,000

352,000

83,200

2,930

Class 10,000

ISO 8

1.0×108

2.37×107

1.02×107

3,520,000

832,000

29,300

Class 100,000

ISO 9

1.0×109

2.37×108

1.02×108

35,200,000

8,320,000

293,000

Room air

GMP EU
classification

Class

maximum particles/m³

under equipped conditions

under equipped conditions

under working conditions

under working conditions

0.5 µm

5 µm

0.5 µm

5 µm

Class A

3,500

0

3,500

0

Class B

3,500

0

350,000

2,000

Class C

350,000

2,000

3,500,000

20,000

Class D

3,500,000

20,000

n/a

n/a

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