User Manual

Siemens Switzerland Ltd 31
Building Technologies Division
Figure 4.4.2-1 Modular and centralized extinguishing systems
Pressure relief in
installation of gas
extinguishing systems
Overpressure flaps are a must when a gas extinguishing system is installed!
Protection of the building
Overpressure flaps prevent the damage from the dangerous overpressure caused
when discharging a gas extinguishing system. An overpressure not vented early
enough can create serious damages to the structure like doors, windows, walls,
equipment and also people who have not evacuated the area.
Ventilation of smoke gases
Overpressure flaps assist venting the toxic smoke gases to free air or to a ducted
canalization system, during the extinguishing flooding process. Thereby avoiding
to the best possible extent, that combustion gases do not flow through leakages
in doors, windows and walls to adjacent areas where injury to personnel is
possible.
Maximum pressure increase
The maximum pressure increase value for a room, without suffering any damage,
must be defined according to the construction of the room (including windows,
doors, firewalls, ventilation openings, etc.) or according to the sensitivity of
equipment to be placed in the room (i.e. computer hard disks). Here the weakest
element defines the maximum acceptable pressure increase.
Higher pressure resistance than 1 mbar, should only be accepted in the project,
with proper consultation with the customer and the customer accepts the
assosciated risks.
Important: When defining the maximum acceptable overpressure in a room, the
relevant specialists should be involved: architects, construction engineers, facility
managers. In practice usually due to architectural, technical or economic reasons,
the venting openings are considered small in size.
This is where the conflict is created that the design goes towards the limit of
maximum admitted overpressure for the room, bringing potential overpressure
problems to infrastructure like computer hard disks or high pressure loads to
doors and walls.
Overpressure flaps must close after the relief of the overpressure!
Overpressure flaps should be positioned in the rooms so that they are not directly
in the direction of the extinguishing agent discharge. Also they should not be
positioned in places where mobile objects can block them or reduce their
efficiency. It is usually recommended that they are placed in the upper third of
the room.