3. Classification of Fire

Fire Safety Book - August 04, 2025

Infographic showing all fire classes with examples and extinguishing methods.

In this post, we welcome you to explore the critical topic of fire classification, where we break down the science behind various fire types and how to combat each one safely and efficiently.

While fire may appear uniform in its appearance—flames, heat, and smoke—its behavior, hazards, and methods of suppression differ greatly depending on the type of material involved in combustion. This led to the development of a universal classification system used by fire protection agencies, safety engineers, and emergency responders worldwide. The classification of fire is essential in identifying the correct firefighting approach, selecting appropriate extinguishing agents, and preventing escalation during fire emergencies. Each class of fire is associated with a particular fuel source and thus requires tailored extinguishing techniques. Misapplying the wrong suppression method—such as using water on an oil or electrical fire—not only proves ineffective but may cause further danger. The following section outlines and explains each recognized class of fire in detail, including Class A, B, C, D, and K/F, based on international standards such as those from NFPA (USA) and IS:2190 (India).

🔥 Types / Classes of Fire

🔴 Class A – Fires Involving Ordinary Combustibles


Wood or paper burning in open air, representing Class A fires.

  • Definition: Fires involving materials like wood, paper, cloth, rubber, and plastics.
  • Fuel Type: Solid organic materials that leave ash.
  • Common Settings: Households, offices, schools, and forests.
  • Extinguishing Method: Water (to cool), Class A extinguishers (foam, water spray).
  • Key Caution: These materials may reignite if not properly cooled.

🟠 Class B – Fires Involving Flammable Liquids and Gases


Fire ignited from spilled gasoline or flammable liquid, showing a Class B fire.

  • Definition: Fires caused by liquids or gases such as petrol, diesel, paint, alcohol, propane, butane, etc.
  • Fuel Type: Flammable or combustible liquids/gases.
  • Common Settings: Fuel stations, chemical plants, garages.
  • Extinguishing Method: Foam, CO₂, Dry Chemical Powder (DCP).
  • Key Caution: Never use water—it can spread the flammable liquid and worsen the fire.

🔵 Class C – Fires Involving Electrical Equipment


Electrical panel or appliance emitting flames and sparks due to short circuit – Class C fire.

  • Definition: Fires originating from energized electrical sources—short circuits, faulty wiring, transformers, appliances.
  • Fuel Type: Electricity (indirect fuel) + surrounding combustible materials.
  • Common Settings: Data centers, offices, industrial units, residential wiring.
  • Extinguishing Method: CO₂ or non-conductive dry powder extinguishers.
  • Key Caution: Disconnect power source before suppression. Never use water on live electrical fires.

🟡 Class D – Fires Involving Combustible Metals


Magnesium or aluminum powder fire showing Class D hazardous metal combustion.

  • Definition: Fires caused by reactive metals like magnesium, titanium, lithium, sodium, potassium, and aluminum dust.
  • Fuel Type: Combustible metallic elements.
  • Common Settings: Laboratories, metal workshops, battery factories.
  • Extinguishing Method: Special Class D dry powder extinguishers (non-water-based).
  • Key Caution: Water or foam reacts violently with these metals—can cause explosions.

⚫ Class K (USA) / Class F (UK & India) – Cooking Oil/Fat Fires


Grease fire on a stovetop from cooking oil, common in domestic or commercial kitchens.

  • Definition: Fires involving cooking oils and fats—common in kitchens and restaurants.
  • Fuel Type: Vegetable oils, animal fats (high flash points).
  • Common Settings: Commercial kitchens, cafeterias, home stoves.
  • Extinguishing Method: Wet chemical extinguishers (potassium acetate-based).
  • Key Caution: Never use water—it causes oil to splatter, leading to fire spread or burns.

Chart showing which fire extinguisher types (water, foam, CO₂, DCP) are used for which fire class.
Conclusion: Why Fire Classification Matters


Understanding the classification of fire is more than academic knowledge in the broader study of fire science. Each class of fire is defined by its unique fuel source, behavior, and the appropriate method of suppression—whether it involves common combustibles, flammable liquids, electrical equipment, reactive metals, or kitchen fats. Recognizing these distinctions is not only essential for selecting the correct fire extinguisher but also for preventing escalation during emergency scenarios. However, knowing what type of fire is burning is only part of the equation. Equally important is understanding how a fire evolves over time, from its initial ignition to its fully developed and decaying stages.

In the next section, we will examine the Stages of Fire Development, a crucial topic for anticipating fire behavior, designing safety protocols, and implementing effective evacuation and suppression strategies.

Post a Comment

0 Comments