Civil Engineering Reference
In-Depth Information
include basements. On these occasions, refl ected
radiated heat, due to the lack of height available, will
develop the fi re more rapidly and raise the growth rate.
The use of sandwich panel walling, containing
polystyrene (used as thermal insulation for areas such
as cold storage facilities), has historically resulted in
rapid fi re growth, due to the substantial heat release of
the building material, i.e. the polystyrene. The failure of
component parts, due to the rapid fi re growth rate of the
materials, also has the ability to destabilise the panels
and cause premature collapse.
Whether included as part of the building construc-
tion or as part of the contents of a building, wall and
surface lining materials also have a direct effect upon
fi re growth rates.
Approved Document B of the Building Regulations
classifi es performance of internal linings. These will be
discussed in future chapters; however, the principles
involve ensuring that the internal linings should adequately
resist the spread of fi re over their surfaces and, if ignited,
a rate of heat release which should be reasonable in the
circumstances.
In this paragraph 'internal linings' means the materials
lining any partition, wall, ceiling, or other internal lining,
such as plasterboard, plaster wall coverings including
paper. Clearly hessian and materials such as polystyrene
tiles have the ability to release large volumes of heat and
thus would greatly affect fi re growth, whereas plaster,
plasterboard, etc. release heat very slowly and would not
adversely affect the fi re growth rate.
is inextricably linked to the supply of oxygen and there-
fore affected by the ventilation of a building. Air condi-
tioning and air circulation systems provide a fi re with
a ready source of oxygen via forced ventilation, which
will aid fi re growth. The presence of dust, vapours and
fumes within the atmosphere also have the ability to
affect the fi re growth rate in so far as they provide a rich
source of fuel. It should also be noted that appropriate
levels of dust in the atmosphere may cause an explo-
sion; this subject is discussed later in this chapter.
When mechanical smoke extraction systems are
utilised within a building the effect of fi re growth is
notably less. The smoke laden air containing particles
of fuel and substantial quantities of heat is removed
from the atmosphere by the extraction system reducing
the speed at which a fi re grows, while assisting smoke
ventilation and allowing persons clear, smoke-free,
escape routes.
Use
The use of a building is directly related to the type of
occupancy. Building use can be categorised in the
following groups:
➤
Offi ces and retail premises
➤
Factories and warehouse storage premises
➤
Sleeping accommodation such as hotels, boarding
houses, etc.
➤
Residential and nursing homes
➤
Teaching establishments
➤
Small and medium places of assembly - public
houses, clubs, restaurants, etc.
Ventilation
As previously discussed the supply of oxygen is critical
to the development and spread of a fi re. Fire growth rate
➤
Large places of assembly (more than 200 persons) -
shopping centres, conference centres, etc.
➤
Theatres and cinemas
External facing or structural support member
Combustible core capable of giving
off toxic combustion products,
e.g. foamed plastic
Sandwich wall panel
with combustible core
Fire-protecting
inner lining,
e.g. plasterboard
Possible route of fire spread
if fire stop absent
Floor or Wall
Fire stop
Fire
Fire
Junctions between sandwich panels and
fire separating walls or floors should
always be fire-stopped
Use wall panels with an effectively fixed
fire-protecting inner facing such as plasterboard
which does not decompose,
disintegrate or shatter in fire
(a)
(b)
Figure 7.21
Cross-section of sandwich panel
