Fire Protection
Procedure & Guidance
Sandwich Panels
Ref
Issue/Revision Date
30/09/2009
Review Date
05/09/2014
Version
FS- NFG021
7.0
Background
This Note for Inspecting Officers provides guidance on the standards that are considered appropriate
in respect to Sandwich Panels.
The Note aims to set general principles and to provide the reader with information as to which
approved document or technical standard is considered by this Authority to be appropriate.
Information
Over recent years there have been a number of increasingly hazardous fires in buildings in which
sandwich panels have been present. The fire at the Sun Valley Poultry in Hereford in September
1993, in which two fire fighters died, focused attention on the use of these panels and their particular
behaviour when involved in fire.
As a result of this, both the Government and industry have been active in carrying out research and
developing guidance to mitigate the risks to occupants and fire fighters, and to reduce the commercial
losses. However, much of this work is for new buildings or major refurbishment. There remain
significant concerns regarding the existing building stock and the safety of fire fighters who must deal
with such fires.
Sandwich panels are being increasingly used in buildings because they are lightweight, energy
efficient, and can be easily handled and rapidly erected. They are used in many buildings ranging from
large factories and warehouses to domestic dwellings. The panels often employ cores made of rigid
foamed plastics because of their thermal conductivity, high moisture resistance and low cost.
Sandwich panels can serve a variety of structural roles. They are usually defined as a secondary
structural element since, unlike beams and columns, which are primary structural elements; they are
rarely designed to transmit dead and imposed loads to the foundation.
Many different core materials may be used in sandwich panels. Board materials include flax board,
foamed glass, compressed mineral wool, foamed phenolic resin, extruded polystyrene and expanded
polystyrene (EPS). Some core materials may be injected between the facings such that they expand
to fill the void and automatically adhere to the facings. Facings may include steel or aluminium sheet,
glass reinforced plastic, glass reinforced cement, gypsum plasterboard or timber based products.
Sandwich panels are often used in prefabricated buildings.
Research To Date
The reader should refer to FRG Publication 3/99 Fire fighting Options for Fires Involving Sandwich
Panels
Studies of the fires in large insulated sandwich panels have been carried out by the Fire Research
Station (FRS) on behalf of the Home Office and the Department of Environment, Transport and the
Regions (DETR). The issue was that panels have been implicated in a number of fires and concerns
have been expressed regarding the risks that they present both to occupants and fire fighters. The
initial review sought to identify the particular fire safety problems with large insulated sandwich panels
by examining recent fire incidents and by visiting some selected working buildings that contain panels.
Causes of fire were found to vary from hot working, to electrical sources, with a small number of
deliberate ignitions.
It would appear that the greatest risk of fire is in food process areas that are bounded by internal
sandwich panel partitions.
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Some laboratory tests have been carried out to examine the ignitability, delamination and general fire
behaviour of the panels with a view to possibly more detailed and extensive tests later. It was intended
that these experiments would include all of the common types of panel currently in use, but this was
not possible since some types of panel are no longer in production. In the event only panels with cores
of polystyrene, fire retarded polyurethane and mineral wool were tested.
All of the panels tested proved difficult to ignite and, once ignited, only the polystyrene core panel
would sustain a fire. The tests indicated that only in exceptional circumstances are sandwich panels
likely to be the item first ignited, however some types could contribute to an already severe fire.
The results of this initial review support the historical evidence that sandwich panels do not present a
particularly high risk to the lives of the general public or to workers in factories containing sandwich
panels, i.e. a no greater risk than that from the other combustibles on the premises.
However, there is a clear unusual risk to fire fighters who may have to enter such a building on fire,
since the fire can spread rapidly within some types of panel and the jointing systems may not prevent
the facing sheets from falling away.
The risks from sandwich panels can be reduced by intelligent use of the panels and by sound fire
safety management.
The sandwich panels identified as presenting the greatest life risk once fully involved in fire are those
consisting of a steel face either side of a foamed polystyrene (EPS), polyurethane (PU) or
polyisocyanurate. However, even panels with non-combustible cores may delaminate, with the
separation of the facing skin from the core. Although the core may be non-combustible, the adhesive
used to bond the core to the facing skin may burn and contribute to fire spread.
As stated previously, the sandwich panels are rarely the item first ignited in a fire; their involvement is
usually secondary and results in a rapidly developing fire in a hidden cavity. Such hidden fires are
amongst the most difficult to extinguish.
It is now widely recognised that sandwich panels are used for internal partitions in the food industry
where food safe surfaces are crucial to the business.
Fire Safety Considerations
It is essential that Fire Protection Officers are ware of: 1. The problems associated with these types of construction e.g.
a) Instability of panel facings when exposed to fire. This can occur irrespective of core
material.
b) Combustibility of the panel core material, particularly after delamination of the outer skin.
2. The recognised approaches to fire safety and fighting fires in such buildings. Although plastic
foamed panels undoubtedly add to the fire load, other important questions need to be addressed i.e.

At what stage in a fire are the sandwich panels likely to become involved?

How long will the panels' joints retain their integrity?

Does the core material melt and produce flaming droplets that could produce secondary fires?

Can fire spread unseen within the core panels?

Are significant amounts of toxic products of combustion released such as to provide a threat to the
life of the occupants and fire fighters, and is the additional smoke obscuration acceptable?
3. Which buildings contain these types of construction (via fire safety and operational inspections)?
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Note/ This type of construction is encountered mainly in the food processing industry but not
exclusively.
4. Be systematic with fire risk assessments. After identifying the fire hazards it is necessary to identify
the risks. This involves deciding the likelihood of fire occurring and the consequences to life, property
and the environment
5. Where risks are recognised or panels identified Fire Protection Officers must liaise with the
Operations Group.
6. Junctions between sandwich panels and fire compartment wall or floors should always be fire
stopped so that fire cannot spread beyond the separating element via the combustible core of the
panel. Intermediate fire stops around the perimeter of each large panel is highly desirable and reduces
the life hazard and potential property loss.
7. Lobby and strongly recommend (require if essential for Means of Escape) effective control
measures, i.e. sprinklers, smoke control, protected bridgeheads for fire fighting.
8. Consider that if ignition occurs, rapid and unpredictable fire spread is likely. Fires may be in areas
that are difficult to trace or detect. Toxic products of combustion and large quantities of dense smoke
will be produced.
9. There is the possibility of early structure failure in single storey constructions.
10. Ceiling panels can be expected to collapse and may also support heavy equipment.
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