4.2 - How Do We Control Fire

Fire is a chemical reaction that produces light and heat, known as combustion. However, it can be dangerous if not controlled properly. Understanding how to control fire is essential for safety. In this section, we will learn the various ways to control fire, based on the principles of combustion.

There are three basic elements required for a fire to occur, commonly referred to as the "Fire Triangle":

• Heat: The energy required to start and sustain a fire.
• Fuel: A material that can burn, such as wood, paper, or petrol.
• Oxygen: A gas that supports combustion, which is present in the air.

In order to control or extinguish a fire, one or more of these elements must be removed or reduced. The following methods can be used to control fire:

1. Removing Heat

If the heat is removed, the fire cannot continue. This can be done by:

• Applying water: Water absorbs the heat from the fire, reducing the temperature below the ignition point.
• Using fire extinguishers: These contain chemicals that absorb heat or lower the temperature of the fire.
• Cooling agents: Other cooling agents such as foam can also be used to absorb heat and suppress the fire.

2. Removing Oxygen

Oxygen is needed for the combustion process. If the supply of oxygen is cut off, the fire will not continue. Some ways to remove oxygen are:

• Smothering the fire: Covering the fire with a blanket or fire-resistant cloth cuts off the oxygen supply.
• Using carbon dioxide (CO₂): CO₂ is a gas that displaces oxygen. Fire extinguishers that use CO₂ help in extinguishing fires by suffocating the flames.
• Using sand: Pouring sand over a small fire can block oxygen from reaching the fuel, thus controlling the fire.

3. Removing Fuel

If the fuel supply is cut off, the fire will not have anything to burn. This method is more applicable to large fires, where:

• Clearing the area: Removing combustible materials such as paper, wood, or other flammable substances from the vicinity of the fire will prevent it from spreading.
• Preventing the spread: Firebreaks, which are gaps in vegetation or other materials, are created to stop the spread of fire, especially in forest fires.

Fire Extinguishers

Fire extinguishers are commonly used to control fires in homes and workplaces. There are different types of fire extinguishers, each designed for specific types of fires:

• Water extinguishers: Used for Class A fires (solid combustibles like wood, paper, etc.).
• Foam extinguishers: Suitable for Class A and B fires (liquids like petrol and oils).
• CO₂ extinguishers: Effective for electrical fires and flammable liquids (Class C and D fires).
• Dry powder extinguishers: Can be used for most types of fires, including electrical and liquid fires.

Fire Triangle and Fire Tetrahedron

While the Fire Triangle shows the three essential elements needed for fire (heat, fuel, and oxygen), the Fire Tetrahedron expands this idea. It adds a fourth element: chemical chain reaction. This reaction occurs at the molecular level during combustion, and without it, fire cannot continue. Therefore, stopping the chemical reaction can also help extinguish a fire.

Fire Safety Tips

It is important to always follow fire safety rules to prevent accidents:

• Always keep fire extinguishers within reach and ensure they are properly maintained.
• Install smoke detectors in your home and check them regularly.
• Avoid placing flammable materials near open flames or heat sources.
• Learn how to use a fire extinguisher effectively, following the PASS method: Pull, Aim, Squeeze, and Sweep.