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Clean room

A cleanroom, also known as an ultra-cleanroom in the highest cleanroom class, is a closed system in which the air is kept as germ- and particle-free as possible. It is used when the normal ambient air is unsuitable or problematic for a particular task, for example in semiconductor production, medical research and treatment or the sterile manufacture of pharmaceutical products.

How it works

In a cleanroom, the number of particles and, if required, the number of germs is constantly monitored - the aim is to minimise the number of airborne particles. To achieve this, processes are used to prevent unwanted particles from being introduced into the room and to remove particles that are already in the air.

Cleanrooms are usually pressurised - this prevents the influx of airborne particles through any leaks. If it is necessary to ensure that no hazardous substances or pathogens penetrate to the outside, cleanrooms are operated with negative pressure. In addition to the pressure, parameters such as temperature and humidity are also permanently monitored and kept constant.

As it is primarily people who introduce particles into the cleanroom, there are special regulations for access to a cleanroom that are designed to minimise the introduction of particles and germs into the cleanroom. Depending on the cleanroom class, employees and visitors must put on protective clothing, undergo cleaning or change clothes several times. In personnel and material airlocks, strong air currents and filter systems swirl up existing particles and extract them. To minimise soiling of objects that come into contact with the floor, for example with shoe soles, special sticky floor mats are often located at the cleanroom entrances.

Objects, materials, tools and machines that are to be brought into the cleanroom must be cleaned beforehand. In addition, special work equipment, tools and corresponding work techniques are used - for example, materials with abrasion-resistant surfaces or lint-free cleanroom paper.

Air conditioning processes and systems are used to remove particles from the air. Specialised air flows in combination with generally multi-stage filtration and a high air flow rate are used to reduce the concentration of particles in the air and prevent particles from being deposited on the product.

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Flow principles for cleanrooms

Two different principles are used for this purpose: low-turbulence displacement flow and turbulent dilution flow.

If the cleanliness requirements are low, it is sufficient to continuously dilute the particle concentration with the turbulent dilution flow. For this purpose, filtered clean air is turbulently supplied to the cleanroom.

However, the least contamination of sensitive work areas and machines is achieved with a laminar flow, the low-turbulence displacement flow: For this, the particle-laden air is displaced from the room. Filtered air flows in continuously and evenly over a large inlet surface and displaces the particle-laden air on the opposite surface out of the room.

Cleanroom classes

Cleanrooms can be classified according to different standards. The most common standards are ISO standard 14644-1 and the GMP guideline Annex 1. According to the EN ISO 14644-1 cleanroom classification, cleanrooms are divided into nine classes, with class 1 being the cleanest. The GMP guidelines differentiate between cleanroom classes A, B, C and D. The strictest requirements are placed on class A. The cleanroom classes are based on the maximum number of particles of a defined size of 0.1 micrometres to 5.0 micrometres per cubic metre of air.

Areas of application

Clean and ultra-clean rooms are required for high-tech manufacturing processes, especially in semiconductor production. However, they are also used in optics and laser technology, nanotechnology, aerospace technology, the life sciences, medical research and treatment, as well as in the sterile production of food and pharmaceuticals.