Cleanroom Classifications

What is a cleanroom?

The most accurate way of answering this question is by quoting the ISO standard definition of a cleanroom. This is the standard which all cleanrooms must conform to and the following explanation gives the defining parameters of a cleanroom -

A cleanroom is a "room within which the number concentration of airborne particles is controlled and classified, and which is designed, constructed and operated in a manner to control the introduction, generation and retention of particles inside the room".

Ref: BS EN ISO 14644-1:2015 Cleanrooms and associated controlled environments - Part 1: Classification of air cleanliness by particle concentration

Cleanroom Classification Table

Cleanroom Standard	Cleanroom Classification Guidelines
ISO 14644-1	Class 3	Class 4	Class 5	Class 6	Class 7	Class 8
Federal Standard 209E	1	10	100	1,000	10,000	100,000
EU GMP	-	-	A/B	-	C	D
Air changes / hour	360-540	300-540	240-480	150-240	60-90	5-48

ISO Classes of air cleanliness by particle concentration

For cleanrooms and clean zones shown in ISO 14644-1:2015

ISO Classification Number	Maximum allowable concentrations (particles/m3) for particles equal to and greater than the considered sizes, shown below
	≥0.1µm	≥0.2µm	≥0.3µm	≥0.5µm	≥1µm	≥5.0µm
ISO Class 1	10b	d	d	d	d	e
ISO Class 2	100	24b	10b	d	d	e
ISO Class 3	1,000	237	102	35b	d	e
ISO Class 4	10,000	2,370	1,020	352	83b	e
ISO Class 5	100,000	23,700	10,200	3,520	832	d,e,f
ISO Class 6	1,000,000	237,000	102,000	35,200	8,320	293
ISO Class 7	c	c	c	352,000	83,200	2,930
ISO Class 8	c	c	c	3,520,000	832,000	29,300
ISO Class 9g	c	c	c	35,200,000	8,320,000	293,000

Cleanroom Limits for Airborne Particulate Contamination

Clean room and clean air device classification, in relation to GMP (2008).

Cleanroom Standard		Maximum permitted number of particles /m³
EU GMP Grade	ISO EN 14644-1	At rest ≥0.5µm	At rest ≥5.0µm	In operation ≥0.5µm	In operation ≥5.0µm
A	5	3,520	20	3,520	20
B	5	3,520	29	352,000	2,900
C	7	352,000	2,900	3,520,000	29,000
D	8	3,520,000	29,000	Not defined	Not defined