Cleanroom technology

Overview of cleanroom standards

2017. January. 31. 17:05 Cleanroom technology

Cleanrooms are special areas or indoor environments constructed by strict regulations. In these areas the occurrence of particles and contamination, the air temperature, the humidity and the pressure ratio are regulated by strict standards. In the air of cleanrooms the allowed maximum occurrence of tenth of a micron and submicron particles are specified too. The main job of a cleanroom is to regulate the number of particles and to keep it on the permitted levels.

Cleanrooms are mostly used in precision mechanics, pharmaceuticals, automobile industry, equipment manufacturing, space technology and other industries, where it is important to maximize the occurrence of particles in the air. In the latest trends the benefits of cleanroom manufacturing is not only known in medical technology, but in laser research and in the food industry too.

Why do we control air?
The reason for this differs from industry to industry. Most of the times the goal is creating a product that is protected of the pollution in the air. For example no one would like to find small particles or dirt behind the screen of their newly purchased phone. But apart from quality assurance there are several other uses of cleanrooms. In the pharmaceutical industry and microbiology it is crucially important to preserve sterility. But in laboratories the main purpose is to prevent the properties of the tested samples from being impacted by anything unnecessary.


Cleanroom standards:


The oldest standard, that has been withdrawn, is the American US FED STD 209E standard. However up until today many multinational company is still specify their requirements based on the values of the FED209E standard.

Class maximum particles/feet3 ISO
≥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

ISO 14644-1

The ISO 14644-1 is the most common, and most modern clean-air standard. It not only specifies the design of cleanrooms, but also the directives for the construction and the methods of usage too. Many manufacturers define their requirements according to the ISO-14644 standard:

Class maximum particles/m3 a FED STD 209E
≥0.1 µm ≥0.2 µm ≥0.3 µm ≥0.5 µm ≥1 µm ≥5 µm
ISO 1 10b d d d d e
ISO 2 100 24b 10b d d e
ISO 3 1,000 237 102 35b d e Class 1
ISO 4 10,000 2,370 1,020 352 83b e Class 10
ISO 5 100,000 23,700 10,200 3,520 832 d,e,f Class 100
ISO 6 1,000,000 237,000 102,000 35,200 8,320 293 Class 1,000
ISO 7 c c c 352,000 83,200 2,930 Class 10,000
ISO 8 c c c 3,520,000 832,000 29,300 Class 100,000
ISO 9 c c c 35,200,000 8,320,000 293,000 Room air

a All concentrations in the table are cumulative, e.g. for ISO Class 5, the 10 200 particles shown at 0,3 μm include all particles equal to and greater than this size.

b These concentrations will lead to large air sample volumes for classification. Sequential sampling procedure may be applied; see Annex D.

c Concentration limits are not applicable in this region of the table due to very high particle concentration.

d Sampling and statistical limitations for particles in low concentrations make classification inappropriate.

e Sample collection limitations for both particles in low concentrations and sizes greater than 1 μm make classification at this particle size inappropriate, due to potential particle losses in the sampling system.

f In order to specify this particle size in association with ISO Class 5, the macroparticle descriptor M may be adapted and used in conjunction with at least one other particle size.


The guidelines of the GMP are probably the strictest. It requires a qualification procedure during operation. Meaning it examines the quality of the cleanroom during the application of methods and procedures used in the manufacturing process. Cleanroom standards don’t only prescribe cleanroom requirements based on the number of particles. Properly designed and built cleanrooms take air exchange rates into account in order to stay within the limits. They also pay attention to the surfaces of the required outlet and extraction points, the cover of these points and the direction of the convections.

Class maximum particles/m3
At Rest In Operation
0.5 µm 5 µm 0.5 µm 5 µm
Grade A 3,520 20 3,520 20
Grade B 3,520 29 352,000 2,900
Grade C 352,000 2,900 3,520,000 29,000
Grade D 3,520,000 29,000 Not defined Not defined

Cleanroom standards therefore include such complex technological directives that help creating a unique cleanroom environment specified for the given industry.

Our company usually qualifies our complex cleanrooms in the as-built stage with accredited institutions, to classify them as cleanrooms. No cleanrooms can be established without qualification and continuous validation. Therefore, our advice for investors is to qualify the cleanroom with a third party institution.

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