User Manual

Fire Safety
57
Building Technologies 049_Archives_and_Libraries_A6
V10271399_a_en.doc
Fire Safety & Security Products 03.2009
4.4.6.3 Post discharge ventilation
Room should be ventilated after an extinguishing discharge has occurred. The air
in the room will not only contain extinguishing agent but also:
– Smoke
– By-products of combustion that may themselves be quite unpleasant (HCl for
example)
– Possibly some agent decomposition products
This must be safely extracted before anyone re-enters the risk. Ventilation can this
be achieved naturally or mechanically.
4.4.7 Protection of ceiling void and raised floors
Archives and libraries are usually built without raised floors or ceiling voids. In case
either of them or both are present, a proper engineering concept should always
consider the entire volume, including raised floors and ceiling voids, to assure the
extinguishing agent concentration and consequently efficiency of the extinguishing
system.
The extinguishing agent concentration in the area to be protected is one of the key
parameters (design concentration). The entire gas extinguishing system design
must aim at establishing the desired concentration within the so-called flooding
time, in the room to be protected.
Of course, it is vital that the room to be protected is capable of allowing the estab-
lishment of the extinguishing agent concentration and maintaining it during the re-
tention time. Decisive here is that the number of unavoidable existing leakage must
not exceed a certain threshold, that would avoid reaching the retention time (10
min. according to VdS, or what local authorities demand) or turns the system un-
economic due to the need of extended discharge to supplement the leakage.
Two methods have proven themselves as control instruments:
1 Real flooding test with concentration measurement devices
2 Door fan test (see chapter Room Integrity, retention time and Door-Fan
Test)
As a rule, the door fan test is preferred over the real flooding test for technical
and/or economic reasons. This test provides an estimate of the leakage area on
the outside
limiting shell of the protected area. Limiting shells are construction
elements that protect the room against the outside and ensure gas tightness. Non-
gas tight structures, partitions, raised floors and ceiling voids are not considered
limiting shells. The above mentioned structures are viewed as non-existent if con-
ducting the door fan method.
The risk of insufficient extinguishing gas concentration may arise if these elements
are not considered when calculating the amount of extinguishing gas required.
Siemens recommends these areas to be considered when calculating the design
volume and to even install extinguishing nozzles in these areas.
Siemens also recommends that ceiling panels are properly closed and secured.
Under no circumstances should the discharging extinguishing agent displace indi-
vidual ceiling panels, which would allow the gas into the ceiling volume. In this
event, the risk arises that the system can no longer establish the required concen-