Cleanroom Classifications

Cleanrooms are classified as 'ISO Class 1' through to 'ISO Class 9' according to the international standard ISO 14644-1.

An 'ISO Class 5' cleanroom, for example, is allowed a maximum concentration of 100,000 particles equal to and larger than 0.1 µm in diameter within the cleanroom (particles/m³ of air).

The table below shows the selected airbourne particulate cleanliness classes for cleanrooms and clean zones:

ISO 14644-1 Cleanroom Standards:

ISO Classification Number	Maximum concentration limits (particles/m³ of air) for particles equal to and larger than the considered sizes shown below
	0.1 µm	0.2 µm	0.3 µm	0.5 µm	1 µm	5 µm
ISO 1	10	2
ISO 2	100	24	10	4
ISO 3	1,000	237	102	35	8
ISO 4	10,000	2,370	1,020	352	83
ISO 5	100,000	23,700	10,020	3,520	832	29
ISO 6	1,000,000	237,000	102,000	35,200	8,320	293
ISO 7				352,000	83,200	2,930
ISO 8				3,520,000	832,000	29,300
ISO 9				35,200,000	8,320,000	293,000

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This table shows a comparison of the various classes that are used internationally:

Cleanroom Class Comparison:

ISO Classification Number	US FED 209E	BS 5295	cGMP (operational)
ISO 1
ISO 2
ISO 3	M1.5 (1)	'C'
ISO 4	M2.5 (10)	'D'
ISO 5	M3.5 (100)	'E' or 'F'	A (B*)
ISO 6	M4.5 (1,000)	'G' or 'H'
ISO 7	M5.5 (10,000)	'J'	B (C*)
ISO 8	M6.5 (100,000)	'K'	C D
ISO 9
			* at rest conditions