User Manual

e1851a

Siemens Building Technologies

Cerberus Division

01.2002

3 Detailed planning of fire detection

systems

3.1 Aim

The early detection of incipient fire in clean rooms and in the related utility installations to

limit damage.

The prevention of false alarms through the use of suitable and tested fire detectors.

3.2 Critical aspects of planning to be taken into

account

The purpose of clean room technology is to maintain a predetermined level of air cleanli-

ness. This is achieved by an appropriate choice of air handling concepts. The air handling

systems provide the room with clean air by means of airflow of varying strength. Here are

the most important points in brief:

Unidirectional airflow

Here air speeds of 0.3 – 0.5 m/s are reached at approx. 600

room air changes/h

Non-unidirectional

airflow

With this type of air handling approx. 10 – 50 room air

changes/h are reached

Continuous operation of

the air handling system

in the clean room

Clean room systems are usually in continuous operation,

even if work is not in progress. The air control principle

must always be maintained. Often the air handling is swit-

ched to 50% capacity outside working hours, e.g. with the

unidirectional airflow at approx. 0.2m/s.

Circulated air The clean room is continually supplied with outside air con-

ditioned by the air handling equipment. Roughly ¾ of this

is returned to the air handling equipment as circulated air.

The remaining quarter is carried off via the workplaces and

processing equipment as processed used air. The monito-

ring of this processed used air is only possible with special-

ly treated heat detectors due to the high contamination

from aggressive and corrosive vapours.

Note: These high rates of change of air are necessary so that the foreign particles in the room are either

swept away by the flow of air or diluted to a tolerable level.