SWANSEA UNIVERSITY – Document Ref: SWG/012A Issue 001
Swansea University
Safe Working Guidelines (SWG)
Fire Prevention
Introduction
These guidelines provide guidance on the prevention of fire in the workplace.
Separate guidelines exist for fire precautions (i.e. means of escape and of raising
the alarm etc.).
The guidelines are based on the main requirements of the Regulatory Reform
(Fire Safety) Order and Highly Flammable Liquids and Liquefied Petroleum Gas
Regulations.
The Fire ‘Triangle’: Three elements are necessary in order for a fire to exist: (a) Oxygen (present in air (21%))
(b) Fuel (the combustible material (in the form of a solid, liquid or gas))
(c) Ignition source (fires cannot be started without a source of heat energy to
cause ignition).
A fire cannot start unless all three are present and a fire will be extinguished
when any one of the three is removed or reduced to a certain level. The fire
triangle illustrates the basic strategy for both preventing and extinguishing fires.
It would be difficult to eliminate air from the workplace so fire prevention usually
depends on keeping heat and fuel apart. Methods of extinguishing fires depend
on the removal or reduction of least one component.
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SWANSEA UNIVERSITY – Document Ref: SWG/012A Issue 001
Fire Terminology
The ‘fire triangle’ shows that heat and air have to be present before fuels will
burn, but how much heat and how much air? For any fuel there are a number of
critical temperatures and fuel/air mixtures at which certain things happen.
Temperature
When fuels (solids or liquids) are heated they evolve vapour and gas. The rate at
which they do so is related to the:
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nature of the material itself
temperature of the fuel
surrounding air pressure
surface area of the fuel.
When these vapours and gases reach their ‘flash-point’ they are capable of being
ignited momentarily by an outside source of heat (spark etc.) but will then go out
as there is insufficient gas or vapour being evolved to continue burning.
If further heat is applied, the gas/vapour will be evolved at a faster rate. When the
fuel reaches its fire-point sufficient gas/vapour is being given off to sustain a
flame when ignited by an outside source of heat (spark etc.).
Fuels that are heated even further will reach their ‘auto ignition’ or ‘self ignition’
temperature when they will ignite without any external source of ignition.
The Spread of Fire
As a fire grows, the amount of heat produced can grow very quickly and will
spread from one source of fuel to another. As the fire grows, other materials will
produce vapours/gases that are both highly toxic and flammable. Due to thermal
expansion these flammable gases are usually under pressure and can pass
through relatively small holes and gaps in ducts and walls, spreading the fire to
other parts of a building. Heat will also be transmitted through walls etc by
conduction.
When the unburned flammable gases reach auto ignition temperature, or are
provided with an additional source of oxygen (e.g. fracture of a window) an
explosive effect called ‘flashover’ takes place.
Ratio of Oxygen to Fuel
Oxygen and fuel (gas or vapour) have to be present in the right proportions
(more correctly within a range of proportions) for ignition to take place. This
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range is known as the ‘flammable range’, its upper limit is called the upper
explosive limit and the lower limit is called the lower explosive limit. The ratio is
only of practical relevance where liquids or gases are in closed vessels.
In open air the fuel air mixture will become weaker in a distance-related gradient.
As long as the fuel is at a temperature above its ignition temperature, an ignitable
mixture will exist somewhere within this gradient. This principle also applies to
combustible solids, as it is the gases/vapours that are liberated at elevated
temperatures that burn.
The Main Causes of Fire in the Workplace
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Electrical faults (poor connections, damaged insulation etc.)
Misuse of electrical equipment (overloaded circuits)
Smokers' materials
Malicious ignition
Oil/gas heating equipment and portable heaters
Unsafe storage of materials
Use of flammable liquids or gases in unsuitable areas
Welding/hot work
Mechanical heat (sparks/friction).
Risk Control Systems and Workplace Precautions
Risk Assessment
Legislation requires that suitable and sufficient assessments are made of the
risks to employees and others from fire at work. These assessments should take
account of any requirements imposed by subordinate regulations. The
assessments should evaluate the adequacy of the existing precautions and
identify any additional precautions required.
Assessments must be reviewed when relevant conditions change, for example:
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numbers of people present
layout of premises
materials/processes/materials stored or used
relevant standards or legislation used in the original assessment.
Minimising the Risk of Fires Starting
Fires are no different to other types of accident; they can be prevented by proper
planning, organisation, procedures, training and monitoring. Reference to the
main causes of fire (above) will identify some obvious precautions, such as: 
proper electrical design and maintenance
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SWANSEA UNIVERSITY – Document Ref: SWG/012A Issue 001
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control over the use of electrical equipment and heaters
discipline regarding smoking
site security
control over contractors
control over hot work (welding, flame cutting, soldering etc)
proper storage and use of flammable materials
The fire triangle (above) shows that fire prevention is based upon:
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Identifying and eliminating potential sources of ignition
Identifying and minimising or controlling sources of fuel
Identifying and minimising or controlling sources of oxygen (i.e. air flows
and oxidising agents).
Reducing Sources of Ignition
Potential sources of ignition should be reduced by:
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removing any unnecessary potential sources of ignition from the
workplace
properly using and maintaining all heat producing equipment
fitting electrical equipment with correctly rated fuses and circuit breakers
where appropriate
ensuring that sources of heat do not arise from faulty or overloaded
electrical or mechanical equipment
operating a permit to work system for maintenance work involving ‘hot
work’ such as welding or flame cutting
prohibiting smoking in areas of fire risk
taking precautions to avoid the risk of arson.
Permit for ‘Hot Work’
Permit systems should be used to ensure that adequate precautions are in place
where maintenance work involves processes that introduce a source of ignition
(e.g. welding, soldering, flame cutting, use of tar boilers).
Minimising the Potential Fuel for a Fire
The potential fuel for a fire should be minimised by:
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replacing flammable materials with less flammable alternatives where
appropriate
reducing flammable materials in the workroom to a minimum required for
operation of the business
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SWANSEA UNIVERSITY – Document Ref: SWG/012A Issue 001
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storing flammable materials in separate fire resisting stores where
appropriate and, where it is necessary to store them in the workroom,
storing highly flammable substances in suitable fire resisting cabinets
ensuring adequate separation distance between flammable materials
ensuring that flammable materials (liquids, gases and solids) are stored,
transported handled and used properly.
Reducing Sources of Oxygen
Sources of oxygen should be reduced by:
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closing doors and windows not required for ventilation
storing any oxidising materials well away from heat sources or flammable
materials.
Minimising the Risk of Fires Spreading
Use of Fire Resisting Materials
The use of materials that are not only non- combustible but which will also resist
high temperatures without catastrophic structural failure is a vital consideration.
These matters are extensively covered in the building regulations.
Various British and European Standards exist which specify the fire resisting
properties of construction materials. Fire resisting doors and panels for example
are usually given a 1-hour or 1/2 hour rating. This means that under test
conditions they withstood the standard test fire for at least that period. Poorly
fitted doors under real fire conditions might not last as long!
Structural steelwork is obviously non combustible but it is likely to buckle and
collapse under typical fire conditions unless protected with a suitable coating, for
example, concrete.
Decorative finishes are particularly important, the use of polystyrene ceiling tiles
for example has been a contributory factor in several major fires in the past.
Compartmentalisation
One of the basic techniques in minimising the spread of fire is to separate
buildings into ‘compartments’. The aim is to ensure that there is a fire-resisting
barrier between compartments. The floors of a multi storey building are usually
connected only by stairs and lift shafts. To maintain compartmentalisation these
must be protected by self-closing, fire resisting doors.
Compartmentalisation is often breached by building modifications and by the
failure to seal cable voids and other gaps. Special ‘intumescent’ sealants are
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available which expand when hot. Ventilation shafts etc. can be protected by fire
automatic shutters operated by fusible links (the fuse melts when hot allowing the
door to self-close); or by honeycombs of intumescent material.
It is vitally important that escape routes are protected form smoke and fire for
long enough to allow time to escape. It is often a requirement under Legislation
to provide a protected escape route (i.e. an escape route which is constructed of
fire resisting material). This requirement depends on the distance from any point
in the building to the final exit (i.e. the open air) and the number of directions in
which to escape.
Storage and Use of Highly Flammable Materials
The ease with which a material will burn is determined by its:
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nature and composition (different materials have different ignition
temperatures etc)
form (e.g. wood shavings ignite more easily than a block of wood because
more heat energy is needed to raise the wood to its ignition temperature)
temperature (this will determine the rate at which gases/vapours are
evolved)
These factors provide some basic rules for storage:
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special precautions must be taken with materials such as flammable
gases and highly flammable liquids
solids are safer when stored in dense packs
flammable materials must be kept cool and away from sources of ignition
an oxygen rich atmosphere will create a high risk of fire
consideration must be given to fire fighting/extinguishing arrangements.
Flammable Gases, Highly Flammable Liquids and Liquefied Petroleum Gas
The Dangerous Substances and Explosive Atmospheres Regulations apply only
to liquids whose flash point is below 32oc, and LPG (i.e. propane and butane).
The precautions required by the regulations might sensibly be applied to other
flammable liquids and gases.
Storage
Highly flammable liquids and LPG must be:
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stored in suitable fixed storage tanks in safe positions; or
stored in suitable closed vessels kept in a storeroom which is either in a
safe position or in a fire resisting structure; or
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SWANSEA UNIVERSITY – Document Ref: SWG/012A Issue 001
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limited to a combined total quantity no more than 50 litres in workroom
(this must be in suitable closed vessels kept in a suitably placed cupboard
or bin, which is itself, a fire resisting structure).
Storage when not in Use
LPG cylinders must be kept in a store when not required for use and empty
cylinders returned to store (part used cylinders which are still connected to
apparatus may remain in the workroom where removal would not be reasonably
practicable).
Marking
Storerooms, tanks, vessels etc. must be marked ‘Highly Flammable Liquid’.
Precautions Against Spills and Leaks
Piped systems are preferred but suitable closed systems are acceptable
provided precautions are taken to avoid spillage/escape of gas or vapour during
transfer.
Ventilation
Adequate ventilation is necessary in both storerooms and workrooms to avoid
the build up of gas or vapour. Ventilation systems must be properly constructed
and maintained.
Sources of Ignition/Smoking
Sources of ignition and smoking should not be permitted where dangerous
concentrations of HFL vapours can be expected to be present.
Solid Residues
Solid residues (lacquer etc.) must not be allowed to accumulate.
Further Information
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Regulatory Reform (Fire Safety ) Order and associated sector guidance
Dangerous Substances and Explosive Atmospheres Regulations
The above guidelines provide advice on the prevention of fire in the workplace.
However, they should not be construed as an exact interpretation of legislative
requirements.
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SWANSEA UNIVERSITY – Document Ref: SWG/012A Issue 001
For additional information, Please contact the Safety Officer or Estates
Department.
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