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Cleanrooms: A class of its own


Thats truly a class of its own!

Which one is better – a cleanroom with cleanliness class ISO 1 or A? And why are they sometimes classified according to numbers and sometimes according to letters? Of course, this makes sense (like most things in the cleanroom industry).

In general – why cleanliness classes?
In cleanrooms, the concentration of particles must be as low as possible. The maximum permissible particle quantity is defined by corresponding standards and must be documented by measurements – both before a cleanroom is commissioned and at defined intervals during operation. The relevant measurement parameters are the number and size of particles per cubic meter of air.

Who defines the limit values?
This is done by the standards DIN EN ISO 14644-1, the EU GMP guidelines (Annex 1) and the supplementary VDI 2083 guideline. They ensure that standards for cleanrooms are comparable.

Cleanliness classes ISO 1 to ISO 9
The DIN EN ISO 14644-1 standard divides cleanrooms into classes ISO 1 to ISO 9 – with 1 being the cleanest class with the lowest particle concentration. This standard is mainly used in industry, for example in the semiconductor industry, medical technology, microelectronics or the automotive sector.
Example: In an ISO 5 cleanroom, a maximum of 3,520 particles measuring ≥0.5 µm per m3 of air may be present while there is not a single one in an ISO 1 cleanroom.

Cleanliness classes A to D
And this is the difference: Cleanliness classes A to D are defined in the EU GMP guidelines (Annex 1). GMP is the abbreviation for “Good Manufacturing Practice” – a collection of standards that primarily defines quality criteria in pharmaceutical production. Cleanliness classes A to D are used in the pharmaceutical, food and cosmetics industries, among others, as the focus is also on microbiological impurities in the air!
Example: In an A cleanroom, a maximum of 3,520 particles measuring ≥0.5 µm per m3 of air may be present – it therefore corresponds approximately to an ISO 5 cleanroom in terms of particle concentration.

Published: October 2023



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  • CAT Group
    (CAT Clean Air Technology GmbH, CAT e-tec GmbH, CAT m-tec GmbH)
    Motorstr. 51 | 70499 Stuttgart
  • Tel: +49 711 3659199 – 0
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