Portable Fire Extinguishers

Fire Dynamics: The A, B, C, D and K’s of Fire

Learning Objective: The student will be able to explain fire types by their letter designations.

One of the first tasks that firefighters and inspectors learn is how to classify fires in accordance with the common letter designations.

Knowing the correct fire type enables one to select the appropriate fire-extinguishing media to safely suppress a fire.

Fires are classified into one of five categories based on the burning products.
Class A – Fires in ordinary combustible materials, such as wood, cloth, paper, rubber, and many plastics.
Class B – Fires in flammable liquids, combustible liquids, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, alcohols, and flammable gases.
Class C – Fires that involve energized electrical equipment.
Class D – Fires in combustible metals, such as magnesium, titanium, zirconium, sodium, lithium, and potassium.
Class K- Fires in cooking appliances that involve combustible cooking media (vegetable or animal oils and fats).

There are circumstances where:
• More than one class of fire may be involved. For example, a liquefied petroleum gas vessel that is venting as a result of a wildland fire exposure would be a combined Class A (vegetation) and Class B (flammable liquid/gas) fire that might require special fire suppression approaches.

• A fire can change from one class to another. Class C fires are those that involve “energized electrical
equipment.” Once the electrical energy is removed, the fire is classified based on the burning material.
A flaming television set becomes a Class A fire when the electricity is disconnected.

With the wide variety of extinguishing agents that exist (e.g., water, dry chemical, dry powder, clean
agent), it is essential to select the correct agent for the fire type.

 

Try the ABCs of Portable Extinguishers