Chapter 7: Portable Fire Extinguishers

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Questions and Answers

What is a Class A fire?

Class A fires involve ordinary combustibles such as textiles, paper, plastics, rubber, and wood.

What can extinguish Class A fires?

These fires can be easily extinguished with water, water-based agents such as Class A foam, or dry chemicals.

What is a Class B fire?

Class B fires involve flammable and combustible liquids and gases, such as alcohol, gasoline, lubricating oils, and liquefied petroleum gas (LPG).

What can extinguish Class B fires?

Agents used to extinguish Class B fires include carbon dioxide (CO2), dry chemical, and Class B foam. Signup and view all the answers

What is a Class C fire?

Class C fires involve energized electrical equipment. Signup and view all the answers

How are Class C fires extinguished?

Class C extinguishing agents will not conduct electricity making them suitable for electrical fires. Once the power supply has been turned off or disconnected, the fire can be treated as a Class A or B fire. Signup and view all the answers

What makes Class C fires more complex than Class A or B fires?

Because water and water-based agents will conduct electrical current, they cannot be used on Class C fires until the electrical energy has been eliminated. Signup and view all the answers

What is a Class D fire?

Class D fires involve combustible metals and alloys such as lithium, magnesium, potassium, and sodium. Signup and view all the answers

How are Class D fires extinguished?

Class D dry powder extinguishers work best on these types of fires; however, dry chemical units should not be used on Class D fires. Signup and view all the answers

What is a Class K fire?

Class K fires involve combustible cooking oils such as vegetable or animal fats and oils that burn at extremely high temperatures. Signup and view all the answers

How can Class K fires be extinguished?

Wet chemical systems and portable fire extinguishers are used to control and extinguish Class K fires. Signup and view all the answers

What are methods of extinguishing a fire?

Smothering, Cooling, Chain breaking, Saponification. Signup and view all the answers

What is the primary use for Pump-type water extinguishers?

On ground cover fires, although they may also be used for small Class A fires. Signup and view all the answers

What class of fire are Wet Chemical Stored-Pressure Extinguishers intended for?

Class K fires involving cooking fats, greases, and vegetable and animal oils in commercial kitchens. Signup and view all the answers

What types of fires can Clean Agent Extinguishers be used on?

They effectively cool and smother fires in Class A and Class B fuels, and can be used on energized electrical equipment (Class C) fires. Signup and view all the answers

What are dry powder agents used for?

Class D fires only. Signup and view all the answers

What is another type of extinguisher that was developed to replace Halon Extinguishers?

Halotron extinguishers are approved by the U.S. Environmental Protection Agency (EPA). Signup and view all the answers

What is a disadvantage of CO2 extinguishers?

Because their discharge is in the form of a gas, they have a limited reach and the gas can be dispersed by wind. Signup and view all the answers

How does a CO2 extinguisher operate?

Carbon dioxide is stored under pressure as a liquefied gas ready for release. The agent is discharged through a plastic or rubber horn. Signup and view all the answers

Why should the hose on wheeled dry chemical extinguishers be fully stretched out?

To prevent difficulty in removing the hose and to avoid clogging of the powder in sharp bends. Signup and view all the answers

Is there any one extinguishing agent that will extinguish any combustible metal?

False Signup and view all the answers

What class fire do dry chemical agents extinguish?

Class D combustible metals. Signup and view all the answers

Are all dry powder agents applied the same?

False Signup and view all the answers

How should dry powder be applied?

In sufficient depth to completely cover the burning area and gently to avoid breaking any crust. Signup and view all the answers

What models do dry powder extinguishers come in?

Handheld and wheeled models. Signup and view all the answers

What are the ratings for Class A?

From 1-A through 40-A. Signup and view all the answers

How is the Class A rating determined?

Based on the amount of extinguishing agent and the duration and range of the discharge used in extinguishing test fires. Signup and view all the answers

What is an example of a 1-A rating conversion?

1-A rating requires 1.25 gallons (5 L) of water. Signup and view all the answers

What is the range for Class B ratings?

From 1-B through 640-B. Signup and view all the answers

How is the Class B rating determined?

It is based on the approximate square foot area of a flammable liquid fire that can be extinguished by a nonexpert operator. Signup and view all the answers

How is the Class C rating described?

Class C extinguishers are rated because they are for fires involving energized electrical equipment. Signup and view all the answers

What are Class C ratings designed for?

Class C ratings confirm that the extinguishing agent will not conduct electricity. Signup and view all the answers

How are Class D ratings established?

Through test fires that consider the reactions between the metal and the agent, toxicity, and effectiveness. Signup and view all the answers

What must Class K fires be capable of?

Saponifying vegetable oil, peanut oil, canola oil, and other oils with little or no fatty acids. Signup and view all the answers

How do wet chemical agents suppress a fire?

By suppressing vapors and smothering the fire. Signup and view all the answers

What is the minimum criteria for a Class K rating?

Agents must extinguish a fire from a deep fryer with a surface area of 2.25 square feet (0.2 m2). Signup and view all the answers

What are common examples of multiple markings?

Class A-B-C, Class A-B, and Class B-C. Signup and view all the answers

What does NFPA 10 pertain to?

Pictographs to identify classes of extinguishers. Signup and view all the answers

How are Class A extinguishers identified?

With a green triangle. Signup and view all the answers

How are Class B extinguishers identified?

With a red square. Signup and view all the answers

How are Class C extinguishers identified?

With a blue circle. Signup and view all the answers

How are Class D extinguishers identified?

With a yellow star. Signup and view all the answers

How are Class K extinguishers identified?

With a black hexagon. Signup and view all the answers

What should you consider when selecting a fire extinguisher?

Classification of the burning fuel, rating of the extinguisher, hazards to be protected, and more. Signup and view all the answers

What must firefighters be cautious around computer equipment related to fire extinguishment?

Do not use dry chemical extinguishers due to corrosive particulate residue. Signup and view all the answers

What must you check immediately before use of a portable fire extinguisher?

External condition, hose/nozzle, weight, and pressure gauge. Signup and view all the answers

What does PASS stand for in relation to fire extinguishers?

Pull, Aim, Squeeze, Sweep. Signup and view all the answers

Study Notes

Types of Fires and Extinguishing Agents

Class A Fires: Involve ordinary combustibles such as textiles, paper, plastics, rubber, and wood. Easily extinguished with water or water-based agents.
Class B Fires: Involve flammable liquids and gases (e.g., alcohol, gasoline). Extinguished using carbon dioxide (CO2), dry chemicals, or Class B foam.
Class C Fires: Involve energized electrical equipment. Must ensure electricity is turned off before treating as Class A or B fire.
Class D Fires: Involve combustible metals (e.g., lithium, magnesium). Identified by bright white emissions; dry powder extinguishers are recommended.
Class K Fires: Involve cooking oils (fats and oils). Found primarily in commercial kitchens and extinguished using wet chemical systems.

Extinguishing Methods

Smothering: Excludes oxygen from the fire.
Cooling: Reduces burning material temperature to below ignition point.
Chain Breaking: Interrupts chemical reactions in the fire.
Saponification: Forms a soapy foam to exclude oxygen.

Properties of Extinguishing Agents

Water: Primarily cools; secondary method is oxygen depletion.
Carbon Dioxide: Primarily depletes oxygen; secondary method is cooling.
Foam: Primarily depletes oxygen; secondary method is vapor suppression.
Clean Agents: Primarily inhibit chemical chains; secondary method is cooling.
Dry Chemical: Primarily inhibits chains; secondary is oxygen depletion.
Wet Chemical: Primarily depletes oxygen; secondary is vapor suppression.
Dry Powder: Primarily depletes oxygen; secondary involves heat transfer cooling.

Types of Extinguishers

Manual Pump Extinguisher: Operator uses a pump to create pressure to expel the agent.
Stored Pressure Extinguisher: Compressed air or inert gas inside the container forces the agent out when the handle is pressed.
Pressure Cartridge Extinguisher: Uses a separate cartridge containing gas to pressurize the agent for discharge.
Common types: Pump-Type Water, Stored-Pressure Water, Wet Chemical, AFFF, Clean Agent, CO2, Dry Chemical, Dry Powder extinguishers.

Specific Extinguisher Functions

Pump-Type Water Extinguishers: Best for ground cover and small Class A fires, used manually.
Stored-Pressure Water Extinguishers: Effective for small Class A fires; pressurized air forces the water out.
Wet Chemical Extinguishers: Designed for Class K fires; uses potassium-based agent to form a foam barrier.
AFFF Extinguishers: Ideal for Class B fires; utilizes foam solution to suppress flammable liquid fires.

Disadvantages and Precautions

Halon Extinguishers: Effective but harmful to the ozone layer; being replaced by clean agents.
CO2 Extinguishers: Limited reach due to gas dispersion; do not require freeze protection.
Dry Chemical Disadvantages: Can obscure visibility and may cause respiratory issues; not all dry chemicals are compatible with foam.

Specific Applications for Extinguishing Agents

Combustible Metals: Class D fires require specific dry powder agents; no single agent is effective for all metals.
Dry Chemical Extinguishers: Common for Class A-B-C fires; should not mix agents to avoid dangerous reactions.
Wheeled Dry Chemical Units: Larger capacity, rated for Class A, B, and C fires; similar operation to handheld units.

Application Techniques

Dry Powder Application: Must cover the burning area sufficiently to create a smothering effect, often requiring a shovel for certain agents.### Fire Extinguishment Techniques
Apply extinguishing agents gently to avoid breaking any crust over burning metal.
Breaking the crust may cause flare-ups and expose more materials to combustion.
Avoid scattering burning metal; it can complicate extinguishment efforts.
Cover small amounts of burning metal on combustible surfaces with powder, followed by additional powder layers as needed.
Develop a 1 to 2 inches (25 mm to 50 mm) deep powder layer for shoveling burning metal onto.
Leave extinguished materials undisturbed until completely cooled before disposal.

Class D Fire Extinguishers

Available in both handheld and wheeled models designed for combustible metals.

Class A Fire Extinguishers

Rated from 1-A to 40-A.
The rating is based on the amount of extinguishing agent, discharge duration, and range.

Class A Rating Conversion

A 1-A rating requires 11/4 gallons (5 L) of water; a 2-A rating needs double that amount, 21/2 gallons (10 L).

Class B Fire Extinguishers

Classified with ratings from 1-B to 640-B.
Ratings reflect the area of flammable liquid fire a nonexpert can extinguish with one full extinguisher.

Class C Fire Extinguishers

No specific fire extinguishing capability tests are conducted for Class C ratings.
Rated because they are essentially for Class A or B fires involving energized electrical equipment.
They ensure that the extinguishing agent does not conduct electricity.

Class D Fire Ratings

Established through tests considering metal reactions, agent toxicity, fume toxicity, and extinguishment times.
Safe and effective agents have application instructions on the extinguisher faceplate, but without a numerical rating.

Class K Fire Extinguishers

Must saponify vegetable and animal cooking oils.
Wet chemical agents work by smothering and vapor suppression.

Multiple Markings on Extinguishers

Common combinations include Class A-B-C, Class A-B, and Class B-C, where each rating operates independently.

Identification of Fire Extinguishers

Class A: Green triangle
Class B: Red square
Class C: Blue circle
Class D: Yellow star
Class K: Black hexagon

Considerations in Fire Extinguisher Selection

Identify the burning fuel classification, extinguisher rating, potential hazards, fire size/intensity, atmospheric conditions, and availability of trained personnel.

Precautions with Computer Equipment

Avoid dry chemical extinguishers near sensitive computer equipment; residues can damage electronics.
Clean agents or carbon dioxide extinguishers are preferable in such environments.

Pre-Use Check for Portable Fire Extinguishers

Evaluate external condition for damage, ensure hose/nozzle is in place, check weight for agent presence, and ensure the pressure gauge is within operable range.

PASS Technique for Fire Extinguishers

Pull the pin to break the seal.
Aim the nozzle at the fire base.
Squeeze the handles to release the agent.
Sweep the nozzle back and forth to cover the burning area.

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Test your knowledge on portable fire extinguishers with these flashcards from Chapter 7. Learn about different classes of fires and the appropriate methods for extinguishing them. Perfect for students and professionals in fire safety training.