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Fire Safety Management > Portable Fire Extinguisher > Flashcards

Portable Fire Extinguisher Flashcards

1
Q

Definition of Portable Fire Extinguishers

A
  • An appliance for use by occupants of a building to fight fires whilst it is still in its early stage of development.
  • Designed to be carried & operated by hand & should have a mass of not more than 20 kg.
  • Contains an extinguishing medium, which is expelled by internal pressure and can be directed at fire.
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2
Q

Provision of Portable Fire Extinguishers

A

Are to be provided for every floor of all buildings except:

  • Purpose Group I: private houses
  • Purpose Group II: flats, apartments & condominiums (residential
    floors)
  • Car parking areas in standalone car parks or mixed-use residential buildings
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3
Q

Limitations of Portable Fire Extinguishers

A
  • Limited amounts of extinguishing medium & hence limited discharge time of extinguisher
  • Limited range of discharging medium
  • Extinguishing medium must be suitable for specific risk application
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4
Q

Classes of fires

A
  • Class A
  • Class B
  • Class C
  • Class D
  • Class F
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5
Q

Class A Fire

A

combustible organic solids like paper, wood, rubber, plastics and cloth.

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6
Q

Class B Fires

A

flammable liquids such as petrol, kerosene, alcohol, solvents and paints.

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7
Q

Class C Fires

A

flammable gases such as propane and butane.

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8
Q

Class D Fires

A

combustible metals such as magnesium & lithium.

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9
Q

Class F fires

A

cooking oils and fats such as olive oil, maize oil, lard & butter.

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10
Q

Electrically energized fires

A
  • Not classified as electricity by itself does not burn but can cause fires in class A, B, C, D and F materials.
  • Extinguishers that contain a non-conductive medium such as CO2 can be used on fires involving energised electrical equipment.
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11
Q

Types of Portable Fire Extinguishers

A
  • water
  • carbon dioxide
  • dry powders
  • foam
  • wet chemical
  • vaporising liquids
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12
Q

Extinguishing Media: Water

A
  • An effective cooling agent, with high specific heat capacity absorbing heat from fire.
  • Especially effective on Class A fires. As water is heavy, its force can knock out a fire.
  • Capable of penetrating into deep seated fires putting out any smouldering embers.
  • Ordinary water extinguishers w continuous jet discharge are not safe for use on other classes of fire, cuz will spread Class B fire, conduct electricity from energised equipment, release explosive hydrogen from Class D fires & will explosively boil over on Class F fires.
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13
Q

Foams

A
  • Detergent/protein-based compounds added to water to produce a film or froth that can float over the surface of Class B fires forming a vapour-proof seal that smothers a fire.
  • Effective on Class A & B fires
  • Allows extinction of a liquid fire & prevents re-ignition.
  • Foams cannot be used on Class D fires.
  • Cannot use on Class F fires as tremendous heat of burning fat destroys the foam blanket rendering it ineffective.
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14
Q

Dry Powders: BC Powder

A
  • Prevent chemical reaction between heat, fuel & oxygen, thus extinguishing fire.
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15
Q

Most common types of powder extinguisher used are

A
  • BC Powder
  • designed for Class B & Class C fires and it does not conduct electricity.
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16
Q

ABC powder

A
  • Consisting of compound that melts & flows to seal & smother Class A fires in addition to its chemical inhibition properties used on Class B & Class C fires.
  • Does not conduct electricity.
  • However, mono-ammonium phosphate compound causes corrosion.
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17
Q

Powder

A
  • Almost multipurpose & knock down most fires in seconds but got drawbacks.
  • Do not cool, reducing effectiveness on Class A fires
  • Discharge is very messy & obscures vision and on Class B fires flames will flashback if the whole fire is not extinguished in one go or if an ignition source remains (unlike foam which is not affected either way).
  • Enclosed electrical equipment is difficult to tackle & powder will damage electronic components by corrosion.
  • ABC powder ineffective on Class F as heat of the oil causes flashback once extinguisher is empty.
  • BC Powder can have a limited effect.
18
Q

Carbon Dioxide (CO2)

A
  • Non-conductive gaseous agent that displaces oxygen to smother a fire.
  • Can use on live electrical equipment as it penetrates & floods enclosures & leaves no residue.
  • However, once gas dissipates, fire can re-ignite, especially if equipment remains live.
  • Effective on small indoor Class B fires, however, re-ignition of hot liquid is possible.
  • Ineffective against Class A, D or F fires.
  • Cannot use in small rooms, as the risk of CO2 poisoning is significant.
  • 4% CO2 concentration is enough to cause symptoms of CO2 poisoning.
  • 8% is enough to kill a person.
19
Q

Wet Chemical

A
  • Alkaline water-based solution of that reacts with burning fat of Class F fire to saponify it & turn surface into a soapy crust, sealing it from the air, allowing it to cool & preventing re-ignition.
  • Produces gentle but highly effective spray and helps prevent hot oil splashing onto user.
20
Q

Vaporising Liquids

A
  • Complex chemical compounds that extinguish fires by chemical inhibition.
  • Most common chemical blend used is HCFC-123 which is safe, effective and environmentally acceptable.
  • Mixed with tetrafluoromethane and argon as propellants.
21
Q

Class A Fire use what

A
  • Water
  • Dry powder
  • Foam
  • Vaporising liquids
22
Q

Class B Fire use what

A
  • Dry powder
  • Foam
  • Carbon Dioxide
  • Vaporizing liquid
23
Q

Class C Fire use what

A

ABC Dry powder

24
Q

Class D Fire use what

A

Depends on type of metal

25
Q

Class F Fire use what

A

Wet Chemical

26
Q

Not Classified Fire use what

A

Carbon dioxide

27
Q

Colour Coding of Water Fire Extinguishers

A

Red

28
Q

Colour Coding of Foam Fire Extinguishers

A

Cream

29
Q

Colour Coding of Dry Powder Fire Extinguishers

A

Blue

30
Q

Colour Coding of CO2 Fire Extinguishers

A

Black

31
Q

Colour Coding of Wet Chemical Fire Extinguishers

A

Yellow

32
Q

Colour Coding of Vaporising Liquids Fire Extinguishers

A

Green

33
Q

Methods of expelling Medium from Extinguisher Body

A
  • Pressure Gauge
  • Gas Cateidge
34
Q

Stored pressure

A
  • Cylinder is permanently pressurised with propellant gas, usually nitrogen.
  • Upon operation a valve is opened allowing pressurised contents to be pushed out.
  • Pressure gauge fitted to indicate pressure inside cylinder.
  • Used for water, dry powders, foam & wet chemical fire extinguishers.
  • CO2 extinguishers also operate using this method with CO2 stored as a liquid under its own vapour pressure.
  • Exception is that CO2 extinguishers don’t have pressure gauge.
35
Q

Gas cartridge pressure

A
  • Internal cartridge of compressed CO2 is screwed into head cap inside main extinguisher body.
  • Upon operation cartridge seal is pierced allowing CO2 inside to pressurise main body & expel contents.
36
Q

Classification of Occupancy Hazards and Size of Fires

A
  • Premises in building are classified according to severity of their hazards.
  • Severity of the hazard will determine rating of fire extinguisher used in premises.
37
Q

Categories of how buildings are classified according to severity of their hazards

A
  • Low hazard
  • Medium hazard
  • High hazard
38
Q

size of small hazard fire

A
  • small fire expected
  • consist of quantities of Class A combustibles and/or total quantity of Class B flammables expected to be less than 5 litres
39
Q

examples of small hazard fire

A

offices, classrooms, places of worships, domestic kitchens etc

40
Q

size of medium hazard fire

A
  • Moderate size fires expected.
  • Consist of Class A combustible
    materials beyond anticipated furnishings, and/or total quantity of Class B flammables expected from 5 litres to 20 litres.
41
Q
A

Fire Safety Management (7 decks)

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