Fire Hazards & Control

WEEK 2 – ELEMENT 5

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The Triangle of Fire

Oxygen HeatSource of ignition

FuelStarving

Smothering

Cooling

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THE FIRE TRIANGLE Extinguishing Fire

1) Cooling the fire by removing the heat

2) Starving the fire of fuel

3) Smothering the fire by limiting the oxygen supply

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SOURCES OF IGNITION Naked flames Electricity (Overheating/Arcing) Smoking materials Hot work (Welding, burning) Chemical reactions (Giving off heat) Heating appliances (Hot surfaces) Friction (Inadequate lubrication) Static electricity Lightning Improper storage of flammable materials Lack of inspection and supervision

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Harm to persons from fire

Main effectsBeing burntInhaling toxic fumesEffects of smoke inhalationDepletion of oxygen supply

Other effectsCollapse of buildingCrush or other injury sustained while escaping

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Flash-point and Flammable

Flash-pointThis is the lowest temperature at which the vapour given off by a substance will ignite when brought in contact with a source of ignition

Fire-pointWhen the fire point is reached sufficient gas or vapour is being given off to sustain a flame when in contact with a source of ignition

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Flash-point and Flammable

Auto-Ignition TemperatureThis is the temperature at which gases or vapour will ignite without any external source of ignition

FlammableLiquids with a flash point between 32oC and 55oC

Highly flammableLiquids with a flash point below 32oC

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Principal Causes of the spread of fire

ConductionMovement of heat through

materials

ConvectionMovement of hotter gases

up through the air

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RadiationTransfer of heat through the air

Direct BurningCombustible materials in contact with naked flame

Principal Causes of the spread of fire

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CAUSES OF FIRE Deliberate (Arson) Electrical faults Misuse of electrical equipment Smokers materials Smoking in prohibited areas Loss of control burning rubbish Heating equipment Unsafe storage of materials Flammable liquids/gases Welding/hot work Mechanical heat (Friction)

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Classification of Fires

Class Type of fuel A Combustible solids

B Flammable liquids or liquified solids

C Flammable gases

D Flammable metals

F Combustible cooking media

Fires involving electrical

equipment

Electrical - classified according to the source of ignition rather than fuel source

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Extinguishing Agents

Class Type of Extinguisher A Water, Dry powder, CO2, Foam

B Foam, CO2 , Dry powder

C Dry Powder, water mist, Foam

D Sand, Soda ash, Talc

F The foam congeals on the top of the oil

Electrical CO2, Dry Powder

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Minimising Risk Of Electrical Fire

Pre-inspection by users Suitability of equipment Inspection/maintenance by competent persons Avoid misuse of equipment Prevent overloading of circuits Correct design and rating for task Isolate if not in use Improved means of protection e.g. RCD High standards of housekeeping Staff awareness training

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Fire Risk Assessment1) Identify hazards:

The three elements of the triangle of fire2) Identify who could be harmed:

Persons at risk particularly the disabled etc.3) Evaluate the risks and adequacy of precautions:-

Considering prevention, protection and precautions

4) Record findings:Prepare an emergency plan

5) Review:If no longer valid

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Factors To Consider In Fire Risk Assessment

Construction and use of building Flammable materials Sources of ignition Work activities generating heat Methods of control Means of fire detection Means of raising the alarm Means of fighting fire/maintenance of equipment Evacuation routes/Protection of routes Numbers of persons at risk Fire prevention training/fire drills

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Prevention, Protection & Precautions

1) Fire Prevention Control measures to reduce the risk of fire

Starting2) Fire Protection

Structural measures to reduce the risk of fire Spreading

3) Fire Precautions Measures taken to reduce the risk in the

Event of fire

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Fire PreventionAim to keep the three sides of the fire triangle apart:Eliminate or reduce the storage of flammable materialsControl of ignition sourcesControl smoking materialsGood housekeepingLubrication of machinery to prevent frictionNo overloading of electrical systemsRegular inspections of electrical systemsVentilation outlets not obstructedControlling hot work with permits etc.Proper storage of flammable materialsSegregation of incompatible chemicalsSecurity to prevent arsonRegular Inspection and supervision

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Storage of Highly Flammable Liquids and Gases

Minimum quantities Suitable fixed storage tanks Keep upright in well ventilated area Clear marking of containers Clearly marked storage area Spillage controls Adequate ventilation Suitable fire fighting equipment Trained competent staff Adequate warning signs

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FIRE PROTECTIONCompartmentation

Splitting a building into separate sealed areas made of fire-resisting materials Restricts the spread of fire and smoke within a buildingDepends upon:

•the use of the building•building height•floor area•compartment volume

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Fire Protection (2)

Fire resistant materials • Primary construction: the main “fabric” of

the building

• Secondary construction: internal partitioning

• Bricks

• Concrete

• Structural steel

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Fire Precautions

a) Fire/smoke detection

b) Fire alarms

c) Means of escape

d) Means of fighting the fire

e) Emergency evacuation procedures

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Fire/Smoke Detection

Smoke detection

Heat/Flame detection

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Fire Alarms Gongs, Bells etc.

Break glass points

Automatic systems:-Continuous detection Alarm sounding

Call the Fire Brigade Indicate location of fireTrigger extinguishers

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Means of Escape - Definition

A means of escape is a continuous path along which a person can travel from wherever he/she may be in the building and reach safety by his own unaided efforts

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Suitability of a Means of Escape Number of employees to use it Any people with special needs Fire resistance of structure Position/Number of escape routes Contents which are readily ignitable Open wells, open staircases Use of building

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MEANS OF ESCAPE – MAIN REQUIREMENTS

Multiple exitsFire resistance of structureAdequate size for numbersTravel distanceClearly marked exitsEmergency lightingExit free of obstructions

Final exit doorUnlocked opening outwardsFire smoke doors self closingFixed stairs to upper floorsExit to safe placeSuitable assembly point

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MEANS OF FIGHTING FIRE Method Aim Means

Remove oxygen Smother the fire Introduces a barrier between the fuel and the oxygen, e.g. a lid, mineral fibre blanket, foam, sand or carbon dioxide

Remove heat Reduce the temperature of the fuel and surroundings to below the ignition temperature

Uses water etc. Some of the heat is transferred to the water and some is used up in the conversion of water to steam

Remove fuel Shut off the supply of flammable gases or liquids

Use of valves etc.

1) Portable extinguishers e.g. hand held or on a trolley2) Fixed installations e.g. Hose reel, flood, sprinklers

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Fixed Fire Fighting Equipment

Hose Reel Sprinkler

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Hose ReelsPermanently connected to the mains water supply. Should be sited in a location which covers the whole area.

Advantages DisadvantagesInexpensive, Effective Harmless to healthUnlimited supply of water at good pressureGreater force than sprinklerOperators need not be too close to the fire

Only suitable for class A fires

Poor siting may cause inadequate coverage

Hose could be kinked

Could stop fire doors closing

May create trip hazards

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Automatic Sprinkler SystemsA network of water pipes with spray heads normally at ceiling height is installed in vulnerable areas

Advantages DisadvantagesLarge coverage of water to prevent the spread of fire in large open plan buildings where compartmentalisation is not practical

Only suitable for Class A firesCauses damage to equipment and furnishings

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Total Flooding SystemsA high concentration of an extinguishing gas (usually carbon dioxide) is automatically dumped in an enclosed area

Advantages DisadvantagesExtinguishes fire without causing unnecessary damage to important equipment such as electrical equipment and computer rooms

Harmful to healthSystem must be disconnected when people enter the protected area

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Portable Fire Fighting EquipmentType Colour

CodeFire Class

Water Red A Cools the fuel and surroundings

Dry powder

Blue All Smothers the fire

Foam Cream B Smothers burning liquids

Carbon Dioxide

Black All Cools and excludes oxygen

Congealing Foam

Canary Yellow

F Cools and excludes oxygen

Fire Blanket

None B Smothers the fire

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Fire Extinguishers (1)Water:- Class ALowers the ignition temperature.Prevents re-ignition.Only to be used on Class A firesFoam:- Class BExcludes oxygen – Blanket effectSuitable for Class B firesAqueous Film Forming Foam

Cream

Red

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Fire Extinguishers (2)Dry Powder:- Class A, B, C

Powder has a smothering effect but no cooling properties

Can be used on all types of fire

Carbon Dioxide:- Class B, EHigh pressure cylinder containing liquified CO2 Liquid vaporises in contact with airSafe to use on electrical fires and burning liquids Black

Blue

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Inspection & Maintenance of Fire Extinguishers

InspectionRoutine (perhaps monthly) visual checks to ensure extinguishers are in place, not been discharged or damaged

MaintenanceInvolves an annual examination by a competent person with the removal and replacement of equipment found faulty and the date of the inspection recorded

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Fire Extinguisher Maintenance

1. Daily checks (Fire Warden)

2) Weekly inspection (Fire Warden)

3) Annually serviced (competent person)

4) Five yearly extended service/discharge

5) Twenty yearly overhaul/replacement

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SITING OF FIRE EXTINGUISHERS

Accessibility Proximity to exits/Escape routes Visibility and signage Located off ground with adequate support Suitable type Protection against damage and weather

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Emergency Evacuation Procedures• Means of raising the alarm• Contacting the emergency services• Fire evacuation routes• Fire evacuation signs• Who are and the role of fire marshals• Assembly points/place of safety/role call• When not to tackle a fire• Types of extinguishers• Prevention of spread of fire e.g. closing fire doors• Not to use lifts• Evacuation in an orderly fashion• Prevention of return• Disabled evacuation procedure

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Practice Drills Practice drills should be undertaken to: Checking alarm can be heard throughout the premises

Testing the effectiveness of the evacuation procedure

Familiarising employees with the alarms etc.

Giving fire wardens to practice their roles Satisfy a legal requirement e.g. fire certificate and to

provide instruction to employees on action to be taken

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Other areas of fire procedures

• Fire Marshals/Wardens• Fire instruction notices• Assembly points• Roll calls• Provision for disabled

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