igc2 elem 5 (fire hazards and controls)
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Fire Hazards & Control
WEEK 2 – ELEMENT 5
NEBOSH Page: 124
The Triangle of Fire
Oxygen HeatSource of ignition
FuelStarving
Smothering
Cooling
NEBOSH Page: 125
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
NEBOSH Page: 126
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
NEBOSH Page: 126
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
NEBOSH Page: 126
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
NEBOSH Page: 126
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
NEBOSH Page: 128
Principal Causes of the spread of fire
ConductionMovement of heat through
materials
ConvectionMovement of hotter gases
up through the air
NEBOSH Page: 128
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)
NEBOSH Page: 128
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
NEBOSH Page: 128
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
NEBOSH Page: 128
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
NEBOSH Page: 129
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
NEBOSH Page: 130
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
NEBOSH Page: 130
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
NEBOSH Page: 131
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
NEBOSH Page: 131
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
NEBOSH Page: 131
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
NEBOSH Page: 132
Fire Protection (2)
Fire resistant materials • Primary construction: the main “fabric” of
the building
• Secondary construction: internal partitioning
• Bricks
• Concrete
• Structural steel
NEBOSH Page: 132
Fire Precautions
a) Fire/smoke detection
b) Fire alarms
c) Means of escape
d) Means of fighting the fire
e) Emergency evacuation procedures
NEBOSH Page: 132
Fire/Smoke Detection
Smoke detection
Heat/Flame detection
NEBOSH Page: 132
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
NEBOSH Page: 133
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
NEBOSH Page: 134
Fixed Fire Fighting Equipment
Hose Reel Sprinkler
NEBOSH Page: 135
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
NEBOSH Page: 135
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
NEBOSH Page: 135
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
NEBOSH Page: 135
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
NEBOSH Page: 136
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
NEBOSH Page: 136
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
NEBOSH
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
NEBOSH Page: 136
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
NEBOSH Page: 137
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
NEBOSH Page: 137
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
NEBOSH Page: 138
Other areas of fire procedures
• Fire Marshals/Wardens• Fire instruction notices• Assembly points• Roll calls• Provision for disabled
NEBOSH Page: 138
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