Fire class is a term used to denote the type of fire in relation to the combustion matter which have or could be ignited. This has onward impacts on the type of suppression extinguishing materials which can be used. Class letters are often assigned to the different types on fire, but these differ between territories. There are separate standards in the United States, Europe, and Australia. 3.2.
Types of Fire and Extinguish methods:
Types of fire:
Class A fires are those fuel by materials that, when they burn, leave a residue in the form of ash, such as paper, wood, cloth, rubber, and certain plastics. Fires of Class B involve flammable liquids and gasses, such as gasoline, paint thinner, kitchen grease, propane, and acetylene.
These are fires in ordinary combustibles such as wood, paper, cloth, trash, and plastics.
Class B fires are fires in flammable liquids such as gasoline, petroleum oil and paint. These fires also include flammable gases such as propane and butane. These fires do not include fires involving cooking oils and grease.
Class C fires are fires involving energized electrical equipment such as motors, transformers, and appliances. Remove the power and the Class C fires becomes one of the other classes of fire.
These fires are fires in combustible metals such as potassium, sodium, aluminium and magnesium.
Class K fires are fires in cooking oils and greases such as animals fats, and vegetable fats.
Others have warnings where it would be dangerous for the operator to use a particular fire extinguishing agent.
- Depending upon the fuel involved the fire is classified into 5 classes:
‘A’ Class Fires: The fuel involved is ordinary carbonaceous solid fuels such as Wood paper Textiles Paper etc.
‘B’ Class Fires: The fuel involved is in liquid form such as Kerosene Oil, Petrol, Oils, etc.
‘C’ Class Fires: The fuel involved is in gaseous for much as Acetylene, Ethylene, LPG, Hydrogen etc.
‘D’ Class Fires: The fuels involved are metals such as Sodium, Potassium. Magnesium etc.
‘E’ Class fires: The fuel Involved is ‘Live’ Electrical equipment’s such as Transformers, Motors Switch boards etc.
‘F’ Class Fires: The fuel involved is ‘Cooking Oil/Fats etc.
Fire Extinguishing Methods:
Fire can be extinguished by employing one or more of the following modes.
This means removal of heat this can be achieved by the use of water. Generally ‘A ‘class fires can be extinguished by this method.
Removal of Fuel. By cutting out the fuel supply to the fire. This can be achieved by physical removal of fuel e. g. pumping out the fuel from the tank on fire or isolating the supply valve etc.
Removal of oxygen (Air) or diluting the same to below the minimum requirement. This can be achieved by applying an inert gas such as C02 or Nitrogen or dry chemical powder or Halons etc.
Chain Breaking Mechanism:
This can be achieved by the application of halogenated hydrocarbons or Dry Chemical Powders.
Suitability of various types of extinguishers for different types of classified fire risks:
|Class of Fire||Material Involved||Mode of Extinction||Type of Suitable Extinguisher|
|A||Ordinary Carbonaceous material (paper, wood, textile etc.)||Cooling’ Blanketing|
Soda Acid Water type (Co2 Cartridge type), Water
( Stored Pressure Type), Water Fire Bucket, Sand fire Bucket
|B||Inflammable liquids ( Benzene, Styrene, kerosene, petrol etc.)||Smothering’ Blanketing Starvation|
Foam BCF, Co2 Dry Powder, Sand Fire Bucket,
BCF Co2 Dry Powder
|C||Inflammable gaseous (Ethylene, H2, LPG, Acetylene etc.)||Smothering Starvation||BCF Co2 Dry Powder|
|D||Metals ( Magnesium, Strontium, Sodium, Potassium etc.)||Smothering||Special Type Dry Powder|
|E||Live Electrical Apparatus (Motors, Switchgear etc.)||Blanketing||BCF Co2 Dry Powder|
|F||All Kitchen Fires (LPG, Kerosene etc.)||Blanketing||1% AFFF Fire Extingisher|
Suitable Extinguishers for each class of fires:
|1||“A” Class Fire||–||Soda Acid/Stored Pressure/Gas Cartridge water |
type extinguishers, Co2 & DCP Extinguishers
|2||“B” Class Fire||–||Foam Extinguishers (Both Mechanical and |
Chemical Foam Extinguishers, Co2 &
|3||“C” Class Fire||–||Co2 Extinguishers|
|4||“D” Class Fire||–||DCP Extinguishers/Sand with sand buckets |
(Composition of DCP has to be change depending
upon the metals under fire)
|5||“E” Class Fire||–||DCP Extinguishers and Co2 Extinguishers |
can also be used.