Ch. 6

Aqueous Film Forming Foam (AFFF) Extinguishers uses

- Class B fires • Useful in combating fires or suppressing vapors from small fuel spills • Most effective on static pools of flammable liquids • Not suitable for Class C, D, or K fuels • Not suitable for flowing fuels or fuel under pressure

Halogenated agents

- Effective for fires containing materials that are easily damaged by water or dry chemicals • Damaging effect on ozone layer

Flammable and combustible liquids and gases include:

Alcohol Gasoline Lubricating oils Liquefied petroleum gas (LPG)

Wet chemical systems and portable fire extinguishers are used to control and extinguish

Class K fires

Saponification

Forming an oxygen-excluding soapy foam surface

The following are commonly used dry chemicals:

Sodium bicarbonate Potassium bicarbonate Urea-potassium bicarbonate Potassium chloride Monoammonium phosphate

Manual pump

The operator physically applies pressure to a pump that increases pressure within the container which forces the agent out a nozzle at the end of a hose.

Stored-Pressure Wet Chemical Extinguishers

They are intended for use on Class K fires involving cooking fats, greases, and vegetable and animal oils in commercial kitchens

Class D fuel examples

Titanium Lithium Magnesium Potassium Sodium

When the extinguishers discharge carbon dioxide, a static electrical charge builds up on the discharge horn.

Touching the horn before the charge has dissipated can result in a shock.

Saponification converts the fatty acids or fats in the following oils to a soapy film:

Vegetable oil Peanut oil Canola oil Other oils with little or no fatty acids

Class A fires can be extinguished by

Water Water based agents- Class A foam Dry chemicals

The Class C rating is assigned in addition to

a rating for Class A and/or Class B fires

Class B fires involve flammable and combustible

liquids and gases

Dry Powder Extinguishers uses

• Class D fires • No agent will work for all combustible metals

Wheeled CO2 units

- Larger than handheld units • Usually have 50- to 100-pound (25 to 45 kg) capacities • Most commonly used in airports and industrial facilities • Operator must wheel unit to fire, then deploy the hose, otherwise operation is same as handheld units

Carbon Dioxide (CO2) Extinguishers- Function and application

- Limited discharge reach • Winds disperse extinguishing agent • Do not require freeze protection • Store CO2 under its own pressure as liquefied gas • Discharges agent through plastic or rubber horn at the end of a hose or tube • Gaseous discharge usually forms dry ice crystals or "snow" • Gas displaces oxygen and smothers the fire • Little cooling effect • Does not suppress surface vapors; fuels may reignite

Aqueous Film Forming Foam (AFFF) Extinguishers differences from stored-pressure water extinguishers:

- Tank contains specified amount of concentrate mixed with water to produce foam solution • AFFF has air-aspirating foam nozzle

The nonexpert operator is expected to extinguish

1 square foot (0.09 m2) for each numerical rating or value of the extinguisher rating

Class A portable fire extinguishers are rated from

1-A through 40-A

Class B portable fire extinguishers are classified with numerical ratings ranging from

1-B through 640-B

To calculate the water capacity of a Class A extinguisher, multiply the number in front of the "A" by

1¼ gallons (5 L). For a 1-A rating, 1¼ gallons (5 L) of water are required

Pressure cartridge

A separate cartridge on the side of the container contains inert gas. When the operator punctures the cartridge seal, the expellant enters the container and forces the agent out a nozzle on the end of a hose

Some common uses of magnesium are in:

Cameras Laptops Luggage Metal box springs for beds Wheels and transmission components for automobiles

Dry Chemical Extinguishers — Wheeled Units uses

Class A, B, and C fires

The three most common combinations of class extinguishers are

Class A-B-C, Class A-B, and Class B-C

Aqueous film forming foam (AFFF) extinguishers are intended for

Class B fires

Water and water-based agents conduct electrical current and cannot be used on

Class C fires until the electricity has been shut off

Fire extinguishing capability tests are not specifically conducted for

Class C ratings

Stored pressure

Compressed air or inert gas within the container forces the agent out a nozzle at the end of a hose when the operator presses the handle.

_________ agents are for use on Class A-B-C fires and/or Class B-C fires; _________ agents are only for use on Class D fires.

Dry chemical; dry powder

Smothering

Excluding oxygen from the burning process

When pressurizing a cartridge-type extinguisher, do not place your head or any other part of your body above the top of the extinguisher.

If the fill cap was not properly screwed back on, the cap and/or a cloud of agent can be forcibly discharged.

Pump-Type Water Extinguishers

Intended primarily for ground cover fires May be used for small Class A fires Usually worn on operator's back Use manually operated slide pump Nozzle produces straight stream, fog, or water-mist pattern

Chemical flame inhibition

Interrupting the chemical chain reaction in the burning process

All portable fire extinguishers expel their contents using one of the following mechanisms:

Manual pump Stored pressure Pressure cartridge

Class A Name

Ordinary combustibles

Water-type extinguishers must be protected against freezing if exposed to temperatures lower than 40°F (4°C).

Protection options include adding antifreeze to the water or storing them in warm areas.

Common portable fire extinguishers include:

Pump-type water extinguishers Stored-pressure water extinguishers Stored-pressure extinguishers Wet chemical stored-pressure extinguishers Aqueous film forming foam (AFFF) extinguishers Clean agent extinguishers CO2 extinguishers Dry chemical extinguishers Dry powder extinguishers

Class D- Testers consider the following factors during each test:

Reactions between the metal and the agent Toxicity of the agent Toxicity of the fumes produced and the products of combustion Time to allow metal to burn completely without fire suppression compared to the time to extinguish the fire using the extinguisher

Cooling

Reducing the burning material below its ignition temperature

There are two basic types of dry chemical extinguishers:

Regular B-C-rated Multipurpose and A-B-C-rated

These fire extinguishers contain a special potassium-based, low-pH agent formulated to operate on the principle of saponification in which the agent combines with the oils to create a soapy foam surface over the cooking appliance.

Stored-Pressure Wet Chemical Extinguishers

Class A/ ordinary combustibles examples

Textiles Paper Plastics Rubber Wood

Water applied to a combustible metal fire results in

a violent reaction that intensifies the combustion and causes bits of molten material to spatter in every direction.

Stored-pressure water extinguishers, also called

air-pressurized water (APW) extinguishers or pressurized water extinguishers

Dry chemical extinguishers are

among the most common portable fire extinguishers in use today

Agents used to extinguish Class B fires include

carbon dioxide (CO2), dry chemicals, and Class B foam

There are two basic designs for handheld dry chemical extinguishers:

cartridge-operated and stored-pressure

Certain extinguishing agents are only effective on

certain classes of fire or fuels

Class K fires involve

combustible cooking oils such as vegetable or animal fats and oils that burn at extremely high temperatures

Class D fires are those involving

combustible metals and alloys

The water/AFFF solution is expelled using

compressed air or nitrogen stored in the tank with the solution

Halons were extremely effective for extinguishing fires in

computer rooms, aircraft engines, and areas that contain materials that could easily be damaged by water or dry chemical agents

The Class C rating confirms that the extinguishing agent will not

conduct electricity

Class C extinguishing agents will not

conduct electricity which makes them suitable for electrical fires

Smothering extinguishing agents will not work on materials that

contain their own oxidizing agent

The Class A foam concentrate serves as a wetting agent and can aid in extinguishing

deep-seated fires in upholstered furniture or vehicle seats and wildland fires in densely matted vegetation

Similar in appearance to standard stored-pressure water extinguishers, stored-pressure water-mist extinguishers use

deionized water as the agent and nozzles that produce a fine spray instead of a solid stream

Do not confuse dry powder extinguishers with

dry chemical units used on Class A, B, and C fires

Class D ____________ extinguishers work best on these types of fires.

dry powder

Class C fires involve

energized electrical equipment

Because impurities in water make it conduct electricity, the deionized water also makes these Class A extinguishers safe to use on

energized electrical equipment (Class C)

To meet the minimum criteria for Class K rating, agents must

extinguish fire with surface area of 2.25 square feet (0.2 m2)

Use only Class D rated fire extinguishers to

extinguish metal fires

AFFF finished foam

floats on fuel surfaces and creates a vapor seal to prevent reignition

Some manufacturers add Class A foam concentrate to pump-type or stored-pressure water extinguishers to

increase their effectiveness

Firefighters may encounter these (Type K) fuels in

private homes, commercial and institutional kitchens, and industrial cooking facilities

Class A foam concentrate reduces the surface tension of water, allowing the water to

quickly penetrate the surface

Do not apply AFFF foam directly onto the fuel • Allow foam to

rain down onto fuel's surface or deflect foam off nearby object

Class D agents do not

receive a rating for use on other classes of fire

Fine spray enhances water's cooling and soaking characteristics and

reduces scattering of burning material

Class K rated extinguishers work because of

saponification

Wet chemical agents containing an alkaline mixture, such as potassium acetate, potassium carbonate, or potassium citrate, suppress the vapors and

smother the fire

AFFF extinguishers are most effective on

static pools of flammable liquids

Fire extinguishers are often

suitable to extinguish more than one class of fire while some are only designed for a particular class of fire

The Class A rating of extinguishers is primarily based on

the amount of water and the duration and range of the discharge used in extinguishing test fires

When an extinguishing agent is determined to be safe and effective for use on a combustible metal, manufacturers include

the application instructions on the faceplate of the extinguisher; they do not give a numerical rating

Class B extinguisher's rating is based on

the approximate square foot (square meter) area of a flammable liquid fire that a nonexpert operator can extinguish using one full extinguisher

Magnesium fires can be identified by

the bright white emissions during the combustion process

The use of water or water-based agents on Class D fires will cause

the fire to react violently, emit bits of molten metal, and could injure nearby firefighters

An extinguisher should be used only for

the fire type(s) for which it is intended

Select extinguishers that minimize

the risk to life and property and are effective in extinguishing the fire

Test fires for establishing Class D extinguisher ratings vary with

the type of combustible metal tested

In addition to being rated according the type of fire they will extinguish, portable fire extinguishers are also rated according to

the type of extinguishing agent and the mechanism used to expel the contents

Portable fire extinguishers are classified according to

the type of fire that each is designed to extinguish

Once the power supply has been turned off or disconnected, firefighters can

treat the fire as a Class A or B fire

Dry Chemical Extinguishers — Wheeled Units function and operation

• Agent in one tank and pressurizing gas in a separate cylinder • Position the unit, then stretch hose out completely • Introduce pressurizing gas into agent tank and allow it to pressurize before opening the nozzle • Significant nozzle reaction • Agent is applied in same manner as handheld, cartridgetype dry chemical extinguishers

Dry Chemical Extinguishers application

• Application may result in cloud of airborne particulate • Agents are nontoxic • Particulate cloud may reduce visibility and create respiratory problems • Class A fires — Direct agents at the fuel to cover it • Once flames are knocked down, apply agent intermittently on smoldering areas

Clean Agent Extinguishers uses

• Cool and smother Class A and B fires • Inhibit sustained chemical reaction in Class C fires • Nonconductive and can extinguish Class C fires • Developed to replace Halons

Carbon Dioxide (CO2) Extinguishers uses

• Handheld or wheeled units • Most effective for Class B and C fires

Dry Chemical Extinguishers- Additives and agents

• Make agents moisture-resistant and prevent them from caking • Keeps agents ready to use after long storage time • Many agents can be mildly corrosive • Some compatible with foam

Dry Powder Extinguishers- function and operation

• Powdered agents applied with handheld or wheeled extinguishers or a shovel or scoop • Completely cover burning area with the agent • Apply agent gently • Avoid scattering burning material • Additional applications as needed to cover hot spots • After extinguishment, leave material undisturbed until it is completely cooled

Handheld Cartridge operated:

• Pressure cartridge connected to agent tank • Operator pushes plunger to release gas from cartridge and pressurize the tank • Uses nitrogen or carbon dioxide as the pressurizing gas

Handheld stored-pressure:

• Similar design to air-pressurized water extinguishers • Agent storage tank maintains constant pressure of about 200 psi (1 400 kPa) • Uses nitrogen or carbon dioxide pressurizing gas

Stored-Pressure Water Extinguishers uses

• Small Class A fires • Small hot spots during overhaul

Stored-Pressure Water Extinguishers function

• Store water and compressed air or nitrogen • Gauge on valve assembly displays the pressure level • Stored pressure forces water up siphon tube and out the hose

halotron extinguisher

• U.S. EPA approved alternative clean agent • Does not harm the ozone