6. Classes of fire and control

 

We know the fire triangle where all three components (oxygen, fuel, heat) are essential for a substance to burn. The absence of any one element ceases the reaction by causing a fire.

 

  

 

We have six different classes of fire based on the combustible material or material that is burning. Based on the flammable materials, we have different types of fire extinguishers which can control fire. Some of the common classes of fire in commercial areas are:

 

Class A: Organic combustible materials(wood, coal, books, etc.)

Class B: Combustible liquids and gases.

Class C: Electrical fire (short circuit from or electrical spark from equipment's).

Class D: Metallic fire (aluminium, magnesium, sodium, etc.).

Class K: Cooking oil fire or kitchen fire (animal or vegetable oil).

 

 

To choose the correct fire extinguisher for the fire, we must know the classes of fire and the combustible material on ignition. For fire from the electrical equipment's, we need to use ${\mathit{CO}}_2$ as this fire extinguisher to cut off the oxygen supply causing the chain reaction to cease. Using water in this type of fire causes shock to the human body, as water is an excellent conductor of electricity. The ${\mathit{CO}}_2$, water, foam are the types of fire extinguishers that cut off the supply of oxygen to the reaction. Water mist and wet chemical fire extinguishers remove the heating substances, whereas the dry chemical stops the chemical reaction by releasing ${\mathit{CO}}_2$.

 

  

We know a general concept that heavier objects sink, so when the ${\mathit{CO}}_2$ fire extinguisher is used on the fire, it cuts off oxygen around the fire causing it to cease.

 

FIRE-101