Purity Requirements
International standards define specific cleanliness requirements for the operation of controlled environments. The standards and guidelines regulate particle concentration (EN ISO 14644 and VDI 2083) or additionally the bacterial burden on the environments (EU GMP guidelines). Rooms are divided into respective cleanroom classes based on limiting values. Find out about the most important standards and guidelines here. An overview of “Cleanroom classes and standards” is available as a PDF download below.
Definition of the degree of air purity through the determination of limit values
Requirements for purity of room air and cleanliness relating to workplace, process media and employees
DIN EN ISO 14644
DIN EN ISO 14644-1 defines the degree of purity of the air by determining limiting values for the maximum permissible particle concentration per m³ and assigns these to cleanroom classes ISO 1 – 9. ISO Class 1 cleanroom systems achieve the highest purity, ISO Class 9 the lowest.
The standard also takes into account important aspects of planning, operation and control of cleanroom facilities. Developed in the semiconductor industry, the standard has firmly established itself in many high-tech industries. It replaced the older standard US FED STD 209E in 2001.
Cleanroom Classes in Accordance with DIN EN ISO 14644-1
Maximum value of permissible concentrations (particles/m³) equal to or greater than the quantities considered, which are shown below
| ISO classification number (N) | ≥ 0,1 µm | ≥ 0,2 µm | ≥ 0,3 µm | ≥ 0,5 µm | ≥ 1,0 µm | ≥ 5,0 µm |
|---|---|---|---|---|---|---|
| 1 | 10 | d | d | d | d | e |
| 2 | 100 | 24 | 10 | d | d | e |
| 3 | 1.000 | 237 | 102 | 35 | d | e |
| 4 | 10.000 | 2.370 | 1.020 | 352 | 83 | e |
| 5 | 100.000 | 23.700 | 10.200 | 3.520 | 832 | d, e, f |
| 6 | 1.000.000 | 237.000 | 102.000 | 35.200 | 8.320 | 293 |
| 7 | c | c | c | 352.000 | 83.200 | 2.930 |
| 8 | c | c | c | 3.520.000 | 832.000 | 29.300 |
| 9 | c | c | c | 35.200.000 | 8.320.000 | 293.000 |
a) All particle concentrations listed in the table are summation frequency-related, for example, the 10,200 particles at 0.3 μm for ISO class 5 include all particles that are equal to or larger than this particle size.
b) These particle concentrations result from the classification in large air volumes. The procedure for follow-up sampling may be used, see Annex D.
c) Due to a very high particle concentration, information on concentration limits in this area of the table is not meaningful.
d) Sampling and statistical limitations for low concentration of particles have no significance for the classification.
e) Limitations for collected sampling for both low concentration particles and particles larger than 1 μm are not suitable for classification due to possible loss of particles during sampling.
f) To define this particle size in conjunction with ISO class 5, the M-discriptor for macroparticles may be adapted and be used together with at least one other particle size. (See C.7.)
g) This class is only applicable for the “Manufacturing” operating state.
EU GMP Guide
The GMP guideline defines limits for microbiological contamination (CFU) by microorganisms and limits for maximum airborne particle count. A distinction is made between cleanroom classes A, B, C and D. The strictest criteria are set for class A, less stringent criteria apply to the other classes.
The standard has its origins in the pharmaceutical industry, specifically in the manufacturing of sterile medicinal products. The abbreviation “GMP” stands for “Good Manufacturing Practice”. However, the standard is not only applied in the production of medicinal products.
Cleanroom Classes According to EU GMP Guidelines
Maximum particle concentration per m³
| Cleanroom Class | at rest ≥ 0,5 µm | at rest ≥ 5 µm | in operation ≥ 0,5 µm | in operation ≥ 0,5 µm |
|---|---|---|---|---|
| A | 3.520 | 20 | 3.520 | 20 |
| B | 3.520 | 29 | 352.000 | 2.900 |
| C | 352.000 | 2.900 | 3.520.000 | 29.000 |
| D | 3.520.000 | 29.000 | Not specified | Not specified |
Recommended limiting values
for “colony-forming units” CFU for microbiological contamination (a)
| Cleanroom Class | Air sample CFU/m³ | Petri dishes (ø90 mm) CFU / 4 hours (b) | Contact plates (ø 55 mm) CFU / panel | Glove impression 5 fingers CFU / glove |
|---|---|---|---|---|
| A | 1 | 1 | 1 | 1 |
| B | 10 | 5 | 5 | 5 |
| C | 100 | 50 | 25 | – |
| D | 250 | 100 | 50 | – |
(a) = average values
(b) = individual petri dishes can also be deposited for less than 4 hours.
VDI Guideline 2083
The guideline series VDI 2083 “Cleanroom technology” sets out specific requirements in Sheet 1 for the cleanliness of the room air, the workplace (surfaces, machines, tools), the process media (gases, liquids, chemicals) and the employees.
VDI 2083 represents a “recognised technology standard” and refers strongly to ISO 14644-1. However, it supplements these with practical operational aspects, such as energy and cost efficiency or biocontamination. In addition, there are industry-specific notes, such as those for microelectronics, pharmaceuticals or life science applications.