User Manual

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Fire & Security Products
Siemens Building Technologies Group
06.2002
5.2.10 Grid pattern dropped ceilings
Dropped ceilings in the form of grids, trellis-work, or slats, e.g. for decoration purposes, to
act as a screen or to support light fittings, influence the spread of smoke and heat. The
degree to which grid pattern dropped ceilings allow smoke penetration varies according
to the size of the grid openings and the type of fire, i.e. open fire or smouldering fire.
Position B
h
Position A
Void
Ceiling opening
Room monitoring I, II, III
Grid pattern
Fig. 27 Detector arrangement for a grid pattern dropped ceiling
Monitoring
Percentage of grid ceiling
Must grid openings be monitored?
yes / no
Detector arrangement
M
on
i
tor
i
ng
category
P
ercentage o
f
gr
id
ce
ili
ng
opening (uniformly distributed)
yes
/
no
according to Fig. 1
Pos. A Pos. B
I
≤50%
yes x x
or
II
no x
II
>50% yes or no x
III
≤50%
yes x x
III
no x
50 - 70% yes or no x x
>70% yes or no provided h ≥4m
x
x
Fig. 28 Detector arrangement for a grid pattern dropped ceiling
In order to ensure response sensitivity detectors may not be mounted between the upper
and lower covering layers of the grid pattern dropped ceiling, rather in the layer which
forms the ceiling.
Grid pattern ceiling
Fig. 29 Detector arrangement for on a grid pattern dropped ceiling