Types of Fire & How to Extinguish Them (Class A, B, C, D, K/F Explained)
Fire is a chemical reaction — specifically rapid oxidation — that releases heat, light, and various reaction products. But not all fires are the same. Understanding the type of fire is essential because using the wrong extinguishing method can make the fire worse or even explode.
Every fire requires three key components (Fire Triangle):
- Fuel
- Heat
- Oxygen
Extinguishing a fire means removing any one of the three.
Let’s break down the major fire classes and how to handle them safely.
π₯ Class A Fire – Solid Combustible Materials
Examples
- Wood
- Paper
- Cloth
- Rubber
- Plastic (common household plastics)
How they burn
These materials undergo pyrolysis — they break down into volatile gases that burn in oxygen.
How to extinguish Class A Fires
- Water (most effective)
- Cools the burning material below ignition temperature.
- Foam extinguishers
- Smother and cool simultaneously.
- Dry chemical extinguishers (ABC type)
- Work by interrupting the chemical reaction.
π« Do NOT use:
- CO₂ alone (ineffective outdoor; fire may re-ignite)
- Dry sand (very slow)
π₯ Class B Fire – Flammable Liquids
Examples
- Petrol
- Diesel
- Kerosene
- Paint
- Alcohols
- Oils & solvents
How they burn
Flammable liquids burn in their vapours, not the liquid itself.
How to extinguish Class B Fires
- Foam extinguishers (AFFF)
- Create a foam blanket and cut off oxygen.
- CO₂ extinguishers
- Displace oxygen; good for labs, kitchens, and workshops.
- Dry chemical powder (DCP/ABC)
- Interrupt chemical reaction and smother vapours.
π« Never use water
Water spreads the liquid → fire becomes bigger.
π₯ Class C Fire – Flammable Gases
Examples
- LPG
- CNG
- Propane
- Methane
- Hydrogen
- Acetylene
How they burn
Gas leaks create explosive mixtures with air. Ignition causes rapid combustion or explosion.
How to extinguish Class C Fires
- Shut off the gas supply immediately (most important).
- Use CO₂ or Dry Chemical Powder extinguishers.
- Cool nearby objects using water spray to prevent re-ignition.
π« Do NOT use:
- Water jet (can spread burning gas flame)
- Foam
π₯ Class D Fire – Combustible Metals
Examples
- Sodium
- Magnesium
- Potassium
- Aluminium
- Titanium
- Lithium batteries (partial overlap with electrical fires)
How they burn
These metals burn at very high temperatures and react explosively with water.
How to extinguish Class D Fires
-
Special Class-D dry powder extinguishers
- Sodium chloride-based
- Graphite powder
- Copper powder
These smother and absorb heat.
-
Cover with dry sand (only if no extinguisher available).
π« Never use
- Water (causes explosion)
- Foam
- CO₂
These can all react violently with burning metals.
π₯ Class E / Electrical Fires (Now Considered a Source, Not a Class)
Examples
- Short circuits
- Overloaded wires
- Burning computers, appliances, switches
How to extinguish
- Turn off the main power supply.
- Use CO₂ extinguishers.
- Use ABC Dry Chemical Powder extinguishers.
Why not water?
Water conducts electricity → risk of electrocution.
π₯ Class K / Class F Fire – Cooking Oils & Fats (Kitchen Fires)
Examples
- Hot oil
- Deep fryer fires
- Ghee/oil catching fire during frying
How they burn
Superheated oils reach auto-ignition temperature and self-ignite.
How to extinguish Class K/F Fires
- Wet chemical extinguishers (Potassium acetate)
- Create a soapy layer called saponification → smothers the fire.
- Smother with a metal lid
- If small and manageable.
- Turn off the heat source.
π« Never use
- Water (violently splashes oil → fireball)
- Dry powder (less effective on deep oil fires)
Quick Summary Table
| Fire Class | Fuel Type | Best Extinguishing Method | Avoid |
|---|---|---|---|
| A | Solid combustibles | Water, Foam, ABC Powder | CO₂ alone |
| B | Flammable liquids | Foam, CO₂, DCP | Water |
| C | Flammable gases | Shut gas, CO₂, DCP | Water jet |
| D | Metals | Class-D Powder, Sand | Water, Foam |
| E | Electrical sources | CO₂, ABC Powder | Water |
| K/F | Cooking oil/fats | Wet Chemical | Water, DCP |
How to Use a Fire Extinguisher (PASS Method)
Even if you know the fire class, using the extinguisher correctly matters.
P – Pull the pin
A – Aim at the base of the fire
S – Squeeze the handle
S – Sweep side to side
Final Advice
Fire safety is chemistry in action. Knowing the fire type means choosing the right strategy. For homes, schools, and coaching centers, keep:
- 1 ABC Dry Powder extinguisher
- 1 CO₂ extinguisher for electrical areas
- 1 Small fire blanket for kitchen use
If the fire is growing or filling the area with smoke — evacuate immediately and call emergency services.
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