Fire Detection and Suppression Chapter 1 Fire Extinguishing Agents and Portable Fire Extinguishers

Fire Detection and Suppression

Chapter 1

Fire Extinguishing Agents and Portable Fire Extinguishers


1-2

Portable Fire Extinguishers

• First line of defense against incipient fires of limited size

• For a portable extinguisher to be effective, the following requirements must be met:— Extinguisher must be readily accessible.

— Extinguisher must be in working order.

— Extinguisher must be suitable for the hazard

— Operator must know how to use extinguisher.


1-3

Classification of Fires by Burning Characteristics

• Class A: ordinary combustibles

• Class B: flammable and combustible liquids and gases

• Class C: energized electrical equipment

• Class D: combustible metals

• Class K: cooking devices that contain or use combustible vegetable or animal oils and fats


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Extinguisher Symbols

• Pictorial system (Fig. 1.2)

• Letter system (Table 1.1)


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How Extinguishers Are Rated

• UL 711, Standard For Rating and Fire Testing Fire Extinguishers

• Rating criteria— Intended use (fire class)

— Fire fighting capability– Volume and duration of agent discharge

– Range of discharge

– Hydrostatic testing of the agent vessel and discharge hose


1-6

Extinguisher Rating Tests

• Class A— Wood crib test

— Wood panel test

— Excelsior test

• Class B: 2-inch (50 mm) layer of flammable liquid

• Class C: nonconductivity(Continued)


1-7

Extinguisher Rating Tests (cont.)

• Class D: tested for specific types of metals— Magnesium fire tests

— Sodium And Potassium Fire Tests

• Class K: UL Standard 300


1-8

Extinguishing Agents

• Water

• Antifreeze agents

• Alkaline mixtures

• Carbon dioxide (CO2)

• Aqueous film forming foam (AFFF)

• Film forming fluoroprotein (FFFP)(Continued)


1-9

Extinguishing Agents (cont.)

• Halogenated agents

• Halotron and other replacement agents

• Dry chemical agents— Ordinary

– Sodium bicarbonate

– Potassium bicarbonate

— Multipurpose: monoammonium phosphate

— Class D dry powders: NA-X; Met-L-X; Lith-X


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Types of Fire Extinguishers

• Stored-pressure

• Cartridge-operated

• Pump-operated

• Obsolete types— Inverting

— Soldered or riveted shell

— Loaded stream


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Selection and Distribution of Extinguishers (cont.)

• General considerations— Nature of the hazard

— Size of the extinguisher– Light hazard occupancy

– Ordinary hazard occupancy

– Extra hazard occupancy(Continued)


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• Specific considerations— Chemical and physical characteristics of

combustibles

— Potential severity of fire

— Location of extinguisher

— Effectiveness of the extinguisher for the hazard

— Personnel available to operate the extinguisher

— Environmental conditions(Continued)


1-13

Selection and Distribution of Extinguishers

• Specific considerations (cont.)— Anticipated adverse chemical reactions between

the extinguishing agent and the burning material

— Any health and occupational safety concerns

— Inspection and service required(Continued)


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• Class A extinguisher distribution factors; substitutions in ordinary- and low-hazard occupancies

• Class B extinguisher distribution factors— Distance to hazard

— Depth of hazard– Flammable liquid fires without depth

– Flammable liquid fires with depth(Continued)


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• Class C extinguisher distribution factors :— No special rules

— Usually involve Class A or Class B fuels

• Class D extinguisher distribution factors :— Requires analysis of specific metal present

— Travel distance should not exceed 75 feet (25 m)(Continued)


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• Class K extinguisher distribution factors— Employee responsibilities

— Travel distance should not exceed 30 feet (10 m)


1-17

Installation and Placement of Extinguishers

• General guidelines— Visible and well signed

— Not blocked by storage or equipment

— Near points of egress or ingress

— Near normal paths of travel(Continued)


1-18

Installation and Placement of Extinguishers (cont.)

• Installation guidelines— Height from floor

— Temperature of environment

— Snow, rain, corrosive fumes


1-19

Portable Fire Extinguishers on Fire Apparatus

• General requirements:— Proper type for probable hazards

— Accessible

— Proper maintenance

• NFPA 1901, Standard on Automotive Fire Apparatus

(Continued)


1-20

Inspecting, Maintaining, and Recharging Extinguishers

• Infrequent use results in tendency to ignore extinguishers

• Common problems— Misplaced or stolen extinguishers

— Damage from being struck by vehicle

— Lost pressure

— Extinguishers used and replaced without notifying proper authorities

(Continued)


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Inspecting, Maintaining, and Recharging Extinguishers

(cont.)• Inspection: visual check to determine that an

extinguisher is available and operable

• Maintenance: thorough examination and performance of any needed service


1-22

Inspecting Extinguishers

• Check that the extinguisher is in its proper location.

• Ensure that access to the extinguisher is not obstructed by boxes, clothing, storage items, or is otherwise inaccessible.

• Check the inspection tag to determine if maintenance is due.

(Continued)


1-23

Inspecting Extinguishers (cont.)

• Examine the nozzle or horn for obstructions.

• Check lock pins or tamper seals to make sure that they are intact.

• Check for signs of physical damage.

• Check that the extinguisher is full of agent.

• Check that the pressure gauge indicates proper reading.

(Continued)


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• Check collar tag for current information and/or damage.

• Check that required signage is in place.

• Check to see if the operating instructions on the extinguisher nameplate are legible.

• Check that the extinguisher is suitable for the hazard protected.

Inspecting Extinguishers (cont.)


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Maintaining Extinguishers

• Mechanical parts

• Extinguishing agent

• Expelling means


1-26

Recharging Extinguishers

• Importance of following correct schedule

• Using proper extinguishing agent

• Pressurizing

• Moisture contamination in nonwater extinguishers

• Qualifications and training


1-27

Hydrostatic Testing of Portable Extinguishers

• Failure of pressure vessels

• Hydrostatic test: filling the cylinder with water and then applying appropriate pressure by means of a pump— Determining appropriate pressure

— Signs that preclude testing an extinguisher

— Record keeping


1-28

Using Portable Extinguishers

Step 1: Activate alarm system.First, call appropriate fire department.

Second, initiate local alarm.

Step 2: Select a suitable extinguisher.Match extinguisher to fire.

Analyze the type of hazard being protected and provide, in a conspicuous location, an extinguisher of the proper size and type.

(Continued


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Using Portable Extinguishers

Step 3: Activate the extinguisher effectively.

Stored pressure: remove safety pin and squeeze valve handle.

Cartridge: remove nozzle from holder and depress lever that punctures cartridge seal.

Step 4: Apply the extinguishing agent properly.(Continued)


1-30

Using Portable Extinguishers (cont.)

• P.A.S.S. Method— Pull the pin

— Aim

— Squeeze

— Sweep(Continued)


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• Attacking Class A fires— Water-based extinguisher

– Aim stream at seat of fire

– Initial distance = 10–30 feet (3 m to 10 m)

— AFFF extinguisher: same method as water-based

— Multipurpose dry chemical

– Attack fire at base

– Sweep nozzle from side to side

– Coat all fuel surfaces(Continued)


1-32


• Attacking Class B fires— Regular or multipurpose dry chemical

extinguishers– Begin discharge at about 10 feet (3 m), sweeping

leading edge of fire and moving forward.

– Begin second attacks with second full extinguishers.

— C02 extinguishers– Apply at close range, sweeping surface of burning

liquid with overlapping strokes.

– Continue discharge after initial extinguishment(Continued)


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• Attacking Class C fires— Dielectric or nonconductive agent

– Carbon dioxide*

– Water mist*

– Halon

– Dry chemical (involves substantial cleanup)

*Best choices

— De-energize equipment if possible(Continued)


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• Attacking Class D fires— Dry powder agents

– Apply with extinguisher or shovel

– Cover fuel with 2-inch layer

– Avoid disturbing fuel

— Limitations of individual agents(Continued)


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• Attacking Class K fires— Class K fire extinguisher recommended

— Class A:B:C or Class B:C extinguisher: reignition possible

— Application– Begin from distance of 10 to 12 feet (3.5 – 4 m)

– Hold application wand at edge of flames and coat surface of fuel with side-to-side sweep.

– Continue to apply agent until the fire extinguisher is completely empty.

Documents

Fire Detection and Suppression Chapter 1 Fire Extinguishing Agents and Portable Fire Extinguishers