User Manual

29
Siemens Switzerland Ltd
Building Technologies Division
4.2.5. Alarm strategies
General alarm A general alarm is a defined audible signal which is sounded throughout the
building. The alarm is automatically activated by the fire detection system, or
manually from the admission desk (or security manager’s office). In the majority
of historical buildings this should trigger the immediate and total evacuation of
the building.
Staff alarm When the first signs of an incipient fire are detected, only members of staff are
initially informed. This gives the designated staff members a short period of time
to investigate the cause of the alarm and deal with any incipient fire. If the fire
cannot be dealt with within the specified timeframe, then the staff is responsible
for an orderly evacuation procedure in accordance with clear evacuation plans.
The staff alarm function is based on the standard Alarm Verification Concept
(AVC), which is described in detail in the following section. This strategy is
particularly suited to situations where a large number of people may be present
who are not familiar with the layout of the building.
Staged alarms Staged alarms are based on systems capable of generating an ‘alert signal’ and a
different ‘evacuate signal’. Such systems may be applicable in very large or
complex buildings, where the occupants have been trained to distinguish
between these two alarm signals. Generally those people potentially most at risk
are those closest to the point where the fire was detected or where the manual
call point was activated. These people should leave the building immediately and
therefore an ‘evacuate signal’ will be sounded in this area. In other areas of the
building an ‘alert signal’ will be sounded, indicating that people in those areas
will only have to leave the building if it becomes necessary, see “phased
evacuation” (Section 4.4.2).