Portable Fire Extinguishers

© 2008 Delmar, Cengage Learning

Portable Fire Extinguishers

Chapter 11


Introduction• Portable fire extinguishers are intended for use

in incipient stage where water is ineffective– Useful if there is quick access, the correct type is

available, and person is trained– Has fixed amount of suppression agent– Are clearly labeled and require little training

• Rapid access to the extinguisher is critical


Requirements for Fire Extinguishers

• Code requirements exist in all of the model codes for fire extinguishers– Requirements center on use and occupancy

conditions and processes• IFC requires extinguishers installed in almost

every new and existing occupancy classification• NFPA 10 lists the requirements for fire

extinguishers


Fire Extinguisher Classification• Through the classification system, extinguishing

agents matched to fire hazards• Classification designated with letters

– Class A fires: ordinary combustibles– Class B fires. flammable and combustible liquids and

gases– Class C fires: energized electrical equipment– Class D fires: combustible metals– Class K fires: cooking media


Fire Extinguisher Ratings• Class A and B have a number rating to indicate

performance capability of the extinguisher– Expresses how much fire the extinguisher can handle

• Class A extinguishers are tested using a wood crib on fire, allowing it to burn for a time

• Class B extinguishers are tested with a flammable liquid fire in a pan– Flammable liquid is usually heptane

• Class C extinguishers do not receive a rating


Figure 11-1 Wood cribbing for Class A extinguisher test


Figure 11-3 Class C test for conductivity


Types of Fire Extinguishers• Pumped, stored pressure, and cartridge

pressure categories• Many suppression agents:

– Water, foam, carbon dioxide, dry chemical, wet chemical, dry powder, halon, clean agents

• Some agents will not work well with a particular category of extinguisher


Pump Extinguishers• Require manual operation of a pump mechanism

– Creates pressure in the tank to expel extinguishing agent

• Extinguishing agent is either water or antifreeze solution

• Easy to operate and fill• Backpack type extinguisher has external pump

– Mechanism similar to hand-held


Stored Pressure Extinguishers• Mix pressurized gas and extinguishing agent in

the same tank• Gas is above the agent and keeps constant

pressure on the agent• When operated, the pressure of the gas forces

the extinguishing agent out of the tank• Air or nitrogen frequently used as expelling gas• Pressure gauge indicates if pressure is sufficient


Cartridge Pressure Extinguishers• Similar to stored pressure type, but pressurized

gas is in a separate cartridge– Attached to the side of the extinguishing tank

• Activating the extinguisher punctures the cartridge that expels the gas into the tank

• Allows for easy maintenance of certain types of agents– Top removes without dumping the agent or losing the

gas pressure• Good for agents that settle and need stirring


Common Fire Extinguisher Agents• Same agents used in sprinkler and suppression

systems are common in fire extinguishers– Present in smaller amounts


Water• One of the best agents because it absorbs more

heat per pound than any other material• Most effective on Class A fires• Not effective on some fuels; dangerous to use

on others• When used in an extinguisher, extinguisher must

not be exposed to cold


Foam• Good agent for Class A but better for Class B

fires• Foam forms a vapor barrier between the fuel

and the atmosphere• Agent must discharge through special aspirating

nozzle so that air can mix with the agent• Two types of foam:

– Aqueous film-forming foam– Film-forming fluoroprotein


Carbon Dioxide• Carbon dioxide gas effective in Class B and C

fires; limited use on Class A fires• In extinguisher tank, carbon dioxide is a high-

pressure liquid state– Expands to a gas when released

• Depletes the oxygen supply• Must be discharged at close range to the fire

because air movement carries the gas away• Operator must have oxygen supply available to

avoid asphyxiation


Dry Chemicals• Small solid particles propelled by pressurized

gas• When discharged, chemical smothers the

burning material• Not considered dangerous or toxic; do not react

with flammable liquids or gases; not conductive• Once discharged, create a cloud that limits

visibility; may cause respiratory problems• May leave a corrosive residue


Wet Chemicals• Wet chemical agents most effective with Class K

fires• Water-based solutions that mix with potassium

carbonate, potassium acetate, potassium citrate• React with fat in the cooking medium or food to

develop a soapy foam blanket on the surface– Smothers, cools, and extinguishes the fire

• Liquid in the agent cools the cooking media adequately to maintain the foam blanket


Dry Powders• Class D fires present a challenge

– Water is not a good choice because it can react with metals to liberate oxygen and fuel the fire

• Dry powders are one of the most effective agents– No one powder effective on all metals

• Some agents do not work in an extinguisher– Applied by shovel, scoop or by hand


Halon and Other Clean Agents• Halon still in use but less available

– Gradual fade-out for environmental concerns• Leaves no residue; not conductive; more effective

than the same amount of CO2 • Halons are somewhat toxic and exposure can

cause physical problems– Vertigo, loss of agility, loss of coordination

• Two types still in use: 1211, 1301• Inert gases generally safe for humans


Summary• Portable fire extinguishers

– Are intended to suppress small incipient fires– Hold a fixed amount of suppression agent, so access

should be quick– Must have knowledgeable operator

• Extinguishing agent must be suitable for the type of fire

• Three categories of extinguishers: pumped, stored-pressure, cartridge pressure


Introduction• Smoke and toxic gases can migrate outside of the

fire area– Smoke travels along stairways, ducts, corridors, elevator

hoistways, etc.• Spread of smoke and toxic gases can cause much

damage, injuries, and death• Passive design approach uses walls, etc., to create

barriers• Active design approach uses mechanical systems to

exhaust the air


Figure 12-1 Manually operated smoke and heat vent in stairway


Code Required Smoke Control and Smoke Management

• Code-mandated installation of smoke control limited to certain structures

• Many structures facilitate quick evacuation– Significantly compartmentalized to inhibit smoke

travel• Installation of these systems in every structure is

unnecessary• Requirements exist for occupancies with

significant evacuation challenge


Smoke Containment, Removal, and Opposed Airflow

• Basic goal of smoke control is to mitigate the spread of smoke

• Smoke control techniques can be standalone or integrated into a building-wide approach

• Systems use 100% outdoor air for positive pressurization– 100% exhaust to the outdoors for smoke relief

• General approaches: containment, removal, opposed airflow


Containment by Pressure Differentials

• Stairway pressurization: prevents or reduces smoke intrusion into egress stairways

• Floating zone/floor-by-floor pressurization: uses the HVAC system

• Elevator hoistway pressurization: similar to stairway pressurization

• Refuge area pressurization: prevents smoke intrusion into refuge areas


Figure 12-2 This mechanical fan and duct line supply air to pressurize a stairway


Figure 12-3 Air supply grill for stairway pressurization


Figure 12-4 Mechanical fan unit for “sandwich effect” pressurization


Figure 12-5 Exhaust vent in corridor for “sandwich effect” pressurization


Smoke Removal• Best suited for large volume spaces, such as

atriums, indoor stadiums, and airport terminals• Provides vertical cross-flow ventilation from floor

to roof• Large volume spaces have no barriers

– Smoke and toxic gases will rise and spread throughout the area

• Unpolluted air fed at a slower rate than the exhaust system rate– Fed from a level lower than the fire


Figure 12-6 Atrium

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Portable Fire Extinguishers