Fire Extinguisher 

Fire can cause significant damage to property, harm people, and destroy natural resources. A fire extinguisher helps by quickly suppressing small fires from growing large enough that they spread. It can be an important tool in minimizing damage and ensuring safety during the early stages of a fire. 

1.0What is a Fire Extinguisher? 

A fire extinguisher is a portable device meant to put out small fires or control them until such a time when they could be handled by professional firefighters. The component mainly used in making a fire extinguisher is dry Carbon dioxide. There are different Fire extinguisher types that are used depending on the nature and severity of a fire. Some of them are as follows:   

2.0Types of Fire Extinguishers

Water-Fire Extinguishers (Class A)

Used for Solid combustibles (e.g., wood, paper, textiles).

Working Principle: Water cools burning material below its ignition temperature, thus extinguishing fire. However, water shall never be used on electrical fires or flammable liquids since it only creates more hazards.

Carbon Dioxide (CO₂) Fire Extinguishers (Class B & C)

Used for flammable liquids and electrical fires.

Working principle: It works by displacing oxygen so the fire suffocates. The CO₂ does not conduct electricity and doesn't leave any residue. Thus, it is recommended for use in electrical fires or around sensitive equipment.

Dry powder fire extinguishers come in Class A, B, C, and Electrical:

Used for: Types of fires include solid, liquid, gas, and electrical.

Working Principle: It works by covering the fuel, interrupting the chemical reaction process, and stopping the spread of fire. They are quite effective but can be messy.

Wet Chemical Fire Extinguishers (Class F)

Used for: It is used for kitchen fires, especially deep fat fryers and cooking oils.

Working principle: Wet chemical extinguishers produce a fine mist, which cools the flame and chemically reacts with oils or fats to form a soapy layer, thus suffocating the fire.

Foam Fire Extinguishers (Class A & B)

Used for: Solid combustibles and flammable liquids, such as gasoline and oils.

Working Principle: Foam forms a blanket over the fuel, cutting off the oxygen supply and cooling the material. Foam extinguishers are not suited for electrical fires or metal fires.

3.0Working Principle of Fire Extinguisher

Fire Triangle 

To understand how fire extinguishers work, it's important to know the fire triangle. A fire requires three elements to maintain combustion:

• Fuel: The material that is burning.
• Oxygen: The gas that feeds combustion.
• Heat: It is the energy to maintain the chemical reaction.

Fire extinguishers seek to eliminate one of these factors, typically by cooling, suffocating, or inhibiting the chemical reactions.

Working of a Fire Extinguisher

As mentioned earlier, the principle of a fire extinguisher is to remove one of the elements of the fire triangle by: 

• Cooling: In the case of most water and foam extinguishers, cooling extinguishing occurs by bringing the burning material temperature below its ignition point.
• Suffocation: CO₂ and foam extinguishers cut off the oxygen supply to the fire, thereby stopping the combustion process.
• Chemical Inhibition: Dry powder extinguishers, such as sodium bicarbonate, chemically inhibit combustion by coating the fuel with a non-reactive layer.

4.0Fire Extinguisher Uses

The different fire extinguisher types are used based on the type of fire it is used on. The applications include:

• Water extinguishers: for solid combustible materials Class A
• Foam extinguishers: for flammable liquids Class B and solid combustibles Class A
• CO₂ extinguishers: for electrical fires Class C and flammable liquids Class B
• Dry powder extinguishers: for a wide range of fires, including electrical, flammable liquids and solids, Classes A, B, C.
• Wet chemical extinguishers: For kitchen fires, especially deep fat fryers (Class F).
• Class D extinguishers: For metal fires (Class D).

Using a Fire Extinguisher: PASS technique 

The PASS technique is the standard method for using a Fire Extinguisher, and PASS stands for: 

• P – Extract the safety pin from the handle.
• A – Point the nozzle or hose at the base of the fire.
• S – Squeeze the handle to release the extinguishing agent.
• S – Sweeps the nozzle side to side, covering the base of the fire.

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