What is a cleanroom?
Definition. Contamination. Classifications.
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". (ISO 14644-1: Cleanrooms and associated controlled environments - Part 1: Classification of air cleanliness by particle concentration).
Cleanrooms are used in virtually every industry where small particles can adversely affect the manufacturing process or product. They vary in size and complexity, and are used extensively in industries such as semiconductor manufacturing, pharmaceuticals, biotech, medical device and life sciences, as well as critical process manufacturing common in battery, aerospace and optics.
Filtration & Air Flow
The key component is the High Efficiency Particulate Air (HEPA) filter that is used to trap particles that are 0.3 micron and larger in size. All of the air delivered to a cleanroom passes through HEPA filters, and in some cases where stringent cleanliness performance is necessary, Ultra Low Particulate Air (ULPA) filters are used.
Cleanroom airflow patterns can be categorized as either unidirectional or non-unidirectional. When a combination of the two is used it is called mixed airflow. Airflow patterns for cleanrooms of ISO Class 5 and cleaner unidirectional, while non-unidirectional and mixed flow is typical for cleanrooms of ISO Class 6 and less clean.
Unidirectional airflow may be either vertical or horizontal. Both types of unidirectional airflow rely upon a filtered air supply and air return inlets which are nearly opposite one another in order to maintain the airstream in as straight a flow pattern as possible. In both designs, the important design feature is the ability to ensure that the airflow pattern is disrupted as little as possible.
In non-unidirectional airflow cleanrooms, filter outlets may be distributed at equal intervals throughout the cleanroom or grouped over the process cores.
Keeping your cleanroom clean
It can be difficult to maintain the standards of a cleanroom, as everything you bring into the cleanroom is likely to release particles into the air, even your operators. Therefore, operators should be trained to understand contamination control theory and correct behaviour.
Operators enter and exit the cleanroom through airlocks, air showers and/or gowning rooms, and they must wear special clothing designed to trap contaminants that are naturally generated by skin and the body. Depending on the room classification or function, personnel gowning may be as limited as lab coats and hairnets, up to multiple layered coveralls.
Cleanroom clothing is used to prevent substances from being released off the wearer's body and contaminating the environment. The cleanroom clothing itself must not release particles or fibres to prevent contamination of the environment. The type of cleanroom garments used should reflect the cleanroom and product specifications.
ISO 14644 Classification
In essence, the classification in a cleanroom is the result of a balance of competing factors: (1) particles entering the room, (2) particles retained within the room and (3) particles leaving the room.
ISO 14644 specifies the classification of air cleanliness in terms of concentration of airborne particles, related to one or more of three occupancy states, “as-built,” “at-rest” or “operational”.
The cleanliness class will be designated by an ISO Class number, for the considered particle sizes. For our cleanrooms this would typically be ISO 5 to 8, where 5 is the cleanest.
For ISO 7 and higher, particles smaller than 0.5 microns (≥0.1 µm, ≥0.2 µm, ≥0.3 µm) are not taken into consideration. For ISO 5, relatively large sized particles of 5 microns are considered inappropriate to classify an area.
Source: ISO 14644 Standards.
GMP Classification, Eudralex Vol. 4, annex 1
According to Eudralex Volume 4 of "The rules governing medicinal products in the European Union" contains guidance for the interpretation of the principles and guidelines of good manufacturing practices for medicinal products for human and veterinary use, Annex 1, Manufacture of Sterile Medicinal Products, 4 grades can be distinguished.
Grade A: The local zone for high risk operations, e.g. filling zone, stopper bowls, open ampoules and vials, and making aseptic connections.
Grade B: For aseptic preparation and filling, this is the background environment for the grade A zone.
Grade C and D: Clean areas for carrying out less critical stages in the manufacture of sterile products.
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