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Classification and Operation of Fire

Fire

Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. The flame is the visible portion of the fire

Fire Triangle: 


The triangle illustrates the three elements a fire needs to ignite, heat, fuel, and an oxidizing agent (usually oxygen). A fire naturally occurs when the elements are present and combined in the right mixture and a fire can be prevented or extinguished by removing any one of the elements in the fire triangle.


Fire Tetrahedron: The fire tetrahedron represents the addition of a component, the chemical chain reaction, to the three already present in the fire
triangle. Once a fire has started, the resulting exothermic chain reaction sustains the fire and allows it to continue until or unless at least one of the elements of the fire is blocked.

Classification of Fire:

Class A Fire: Ordinary combustible materials such as wood, cloth, paper, rubber and certain plastics etc which when burn, leave a residue in the form of ash
Class B Fire: Flammable Liquids, combustible liquids, petroleum greases, oils, paints, solvents, alcohols and liquefiable solids.
Class C Fires: Fires involving flammable gases under pressure including liquefied gases, where it is necessary to inhibit the burning gas at fast rate with an inert gas, powder or vaporising liquid for extinguishment also involving energized electrical equipment such as Computers, transformers & panel boards etc. Note that if the electricity to the equipment is cut, Class “C” fire becomes Class “A” fire
Class D Fires: Involve combustible metals, such as magnesium, sodium, aluminium, titanium, zirconium and potassium.

Fire Extinguisher:   A portable device that discharges Water, Foam, 


Gas, Dry Chemical powder or other material to extinguish a fire.  


CO2 Fire extinguisher : 

ü  Used for Class “B”- Flammable liquids & Class “C” Flammable gases and Electrical fires
ü  These extinguisher are filled with Non-flammable carbon dioxide Gas under extreme pressure
ü  Recognized by its hard horn and lack of pressure gauge
ü  The pressure in the cylinder is so great that when used, bits of dry ice may shoot out the horn
ü  These extinguishes by displacing oxygen, or taking away the oxygen element of the fire triangle
ü  Distinguished by a “Black” coloured band

DCP Fire extinguisher :  

Dry Chemical Extinguishers come in variety of types, you may be see them labelled:

ü  “ABC” indicating that they are designed to extinguish class A, B and C fires
ü  “BC” indicating that they are designed to extinguish class B and C fires
ü  Common agent for Dry Chemical extinguisher are Mono Ammonium phosphate, Sodium Bicarbonate, Potassium Bicarbonate etc
ü  Nitrogen gas is used to pressurized the extinguisher
ü  Dry chemical extinguishers put out fire by coating the fuel with a thin layer of dust, separating the fuel from the oxygen in the air.
ü  The powder also works to interrupt the chemical reaction of fire, so these extinguishers are extremely effective at putting out fire.
ü  Distinguished by a “Blue” Coloured band.

Operation of Fire extinguisher :  

Activating a fire extinguisher to apply the extinguishing agent is a single operation that involves four steps.

The PASS acronym is a helpful way to remember these steps: 

ü  Pull the safety pin.
ü  Aim the nozzle at the base of the flames.
ü  Squeeze the trigger to discharge the agent.
ü  Sweep the nozzle across the base of the flames





When using a fire extinguisher,
always approach the fire with an exit behind you. If you are outside, make sure the wind is at your back.


Put off the Fire with care

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