Tuesday, 29 December 2015

Triangle of Combustion

Triangle of Combustion 
What is the Fire Triangle?

The fire triangle is used to show the three elements that when present together can cause a fire to start. These three ingredients are fuel, heat and oxygen, under all circumstances they should be kept apart to avoid a fire starting. Understanding the basic principles of the fire triangle is essential in helping to protect your business and prevent fires from breaking out.

How does the fire triangle work?

When fuel or flammable materials are heated, the energy stored inside starts to react with oxygen in the air, giving off heat. This creates a vicious cycle, which causes the fire to spread. To stop the spread of a fire you have to remove one of these elements to break the triangle.

Lighting and preventing fires based on the fire triangle:


This makes up about 20% of the air we breathe, so there is a ready supply to fuel a potential fire if flammable materials come into contact with enough heat to start a fire. Once a fire has started, depriving it of oxygen will weaken extinguish it. This is a principle used by some fire extinguishers. Foam and dry powder extinguishers can be used to smother flames and deprive the fire of oxygen, whereas the CO2 in carbon dioxide fire extinguishers will replace the oxygen to deprive the fuel source of it.
Without a sufficient supply of Oxygen a fire will stop burning, so it’s always handy to keep appropriate fire extinguishers near areas with a high risk of fire. Always use fire extinguishers with care and check that you are using the correct type of fire extinguisher for the type of fire you are dealing with.


All flammable materials have a flash point, this is the lowest temperature at which they will ignite. If you are storing flammables on site then you will need to be aware of their flashpoints and make sure that all materials stored away from sources of heat and under their flash point temperature.
If a fire does break out then having a water fire extinguisher on standby is a good idea. Water has the effect of cooling the fire, thus removing heat from the equation. However remember not to use water on electrical appliances or cooking oil fires.


A fire will continue as long as there is fuel to burn. Fuel comes under three categories, solid, liquid and gas. Each type should be treated specially to ensure that their presence does not result in a fire.
The most common types of fuel are solid materials. Just look around you, everyday materials that surround you such as paper, card, clothing, fabrics and furniture could all be potential fuel for a fire. To reduce the chance of a fire starting, keep these materials away from electric heaters, radiators and direct sunlight.
Liquid fuel and flammable gases require more special attention. Ideally you should keep liquids and gases in a sealed container away from other flammables and possible sources of ignition or heat. You should regularly check for signs of damage to the containers and keep as small an amount as necessary on site. 
Of course following these tips can only help reduce the chance of a fire breaking out, so it is strongly advised to only keep flammable liquids and gases are absolutely needed and if no non-flammable alternative is available.
Once a fire has started it is very difficult to remove the fuel, but wet chemical fire extinguishers which are specially designed for cooking oil and grease fires can achieve this. The chemicals released react with oil to form non-combustible soapy layer, which stops the spread of fire in its tracks.
Each year there are many non-domestic fires that could have easily been prevented. By understanding the basic principles of the fire triangle you can ensure that your business is best prepared to avoid potential disaster caused by fire.

Types of Fires

Not all fires are the same. Different fuels create different fires and require different types of fire extinguishing agents.

Class A fires 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. Class B fires also includeflammable gases such as propane and butane. Class B fires do not include fires involving cooking oils and grease.
Class C fires are fires involving energized electical equipment such as motors, transformers, and appliances. Remove the power and the Class C fire becomes one of the other classes of fire.
Class D fires are fires in combustible metals such as potassium, sodium, aluminum, and magnesium.
Class K fires are fires in cooking oils and greases such as animals fats and vegetable fats.

Some types of fire extinguishing agents can be used on more than one class of fire. Others have warnings where it would be dangerous for the operator to use a particular fire extinguishing agent.
Posted by Indian Safety Association 

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