User Manual

Fire Safety
52
Building Technologies 049_Archives_and_Libraries_A6
V10271399_a_en.doc
Fire Safety & Security Products 03.2009
4.4.6 Pressure relief in installation of gas extinguishing systems
4.4.6.1 Pressure relief
Pressure relief flaps are a must when a gas extinguishing system is installed!
Protection of the building
Pressure relief flaps prevent damage from the dangerous overpressure caused
when releasing a gas extinguishing system. An overpressure not vented early
enough can provoke serious damages to the structure like doors, windows, walls,
equipment and also people who have not been able to evacuate the area.
Ventilation of smoke gases
Pressure relief flaps assist venting the toxic smoke gases to free air or to a ducted
system, during the extinguishing flooding process. Thereby avoiding to the best
possible extent, that combustion gases flow through leakages in doors, windows
and walls to adjacent areas where damage to people could be caused.
Maximum pressure increase
The maximum pressure increase value for a room, without suffering any damages,
must be defined according to the construction of the room (including windows,
doors, firewalls, ventilation openings, etc.)
Light Building Construction 100 Pa = 1 mbar
Normal Building Construction 300 Pa = 3 mbar
Heavy Building Construction 500 Pa = 5 mbar*
Tab. 10 Maximum pressure
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 architectonic, technical or economic reasons,
the venting openings are considered small.
Pressure relief flaps must close after the relief of the overpressure!
Pressure relief flaps should be positioned in the rooms so that they are not directly
in the direction of the extinguishing agent discharge. Also should not be position in
places where mobile objects can block them. It is usually recommended that they
are placed in the upper third of the room.
4.4.6.2 Pressure relief – function and types
The enclosure must be of suitable strength to withstand the pressure changes
which occur inside the enclosure during the discharge of the extinguishant.
Inert gases exert a positive pressure on the enclosure
Fig. 22 Pressure on enclosure