User Manual

e1851a

Siemens Building Technologies

Cerberus Division

01.2002

6 Detailed information on clean room

technology

6.1 Flow control in the clean room

The sources of particulate air contamination in workrooms are

D the outside air

D the air handling systems and

D the release of particles in the workrooms themselves (e.g. through work processes, per-

sonnel, expendable material, cleaning agents, maintenance work etc.)

Certainly filtering the air for floating particles creates an air supply of outstanding quality,

however, nothing can be done against the release of minute objects and microorganisms in

the workrooms.

Therefore, airflow techniques are implemented to counter the air contamination released in

the rooms themselves.

6.1.1 Non-unidirectional airflow

If the level of air cleanliness demanded is not too high, then it is sufficient to dilute the con-

tamination released in the air in the room with an adequate fresh air supply (first air) filtered

for floating particles. This is achieved by means of the principle of non-directional airflow.

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Legend:

1 Pre-treated outside air

2 Extract air

Fig. 13 Section through clean room with non-unidirectional airflow

With suitable floating particle filters and comparatively moderate air supply (10 – 50 air

changes/hour) the requirements for air cleanliness classes 10,000 and 100,000 (ISO 7 and

ISO 8), and if particular care is taken even class 1000 (ISO 6) can be met (See section 6.6

for a definition of air cleanliness classes).