Fires are often unpredictable, destructive, and can cause tragic loss of life. Understanding how fire works can help us prevent it, predict it, and control it. One of the most basic concepts in fire safety is the fire triangle.
What is the fire triangle?
The fire triangle is a simple model that explains what elements need to be present for a fire to ignite and burn. It consists of three elements: heat, fuel, and oxygen. Without either of these three, a fire cannot start or sustain itself.
Heat: The First Element
Heat is necessary to ignite a fire. It can come from a variety of sources, including open flames, electrical sources, and friction. Once ignited, a fire will continue to produce heat, causing it to spread and intensify. This heat can cause burn injuries or ignite other combustible materials. The heat generated is what sustains the fire and keeps it burning.
Flash Point vs Fire Point
Heat also plays a vital role in determining the flash point and fire point of a material. The flash point is the temperature at which a material will ignite, while the fire point is the temperature at which the material will continue to burn. Knowing these points is important in preventing fires by understanding the danger of specific chemicals and materials.
Sources of heat
Sources of heat can be natural or man-made. The sun and lightning strike are examples of natural sources of heat. On the other hand, some man-made sources include welding equipment, cooking appliances, and matches. It is essential to be careful when using these sources not to ignite any flammable materials around them.
Fuel: The Second Element
Just like how a car needs fuel to run, a fire also needs fuel to sustain itself. Fuel refers to any combustible material that can burn when exposed to heat and oxygen.
Various types of fuels contribute to fires, ranging from natural materials such as wood, paper, and leaves to synthetic materials like gasoline and plastic. It is essential to note that different fuels burn at different rates and temperatures, producing various flames and smoke.
A flashover is a deadly phenomenon that occurs when all combustible materials in a room reach their ignition temperature simultaneously. When this happens, the heated gases burst into flames, creating a massive fireball that engulfs the room.
On the other hand, backdraft is a similar condition that occurs when oxygen- deprived fire conditions suddenly get access to fresh air, causing a violent explosion. Backdrafts are explosive and can cause severe harm to anyone in their vicinity.
Oxygen: The Third Element
Fire needs three elements to ignite and sustain: heat, fuel, and oxygen. The role of oxygen in a fire is to help oxidize or break down fuel molecules into smaller combustible compounds, releasing energy and heat. The oxygen contained in the surrounding air diffuses in and reacts with the fuel, making the fire hotter and brighter. Oxygen acts as an oxidizer, and without it, fires wouldn’t exist. Oxygen supports combustion, and an adequate supply of oxygen can make the flame burn brighter, hotter, and faster.
During a fire, there is a constant supply of oxygen as it diffuses from the surrounding air. The amount of oxygen present can influence the rate and intensity of the flame. To extinguish a fire, you can remove the oxygen supply by smothering the flame with an agent that blocks out the oxygen supply. In wildfires, oxygen concentration along with moisture and wind plays a crucial role in determining fire intensity and spread.
The Fire Tetrahedron is an extension of the Fire Triangle, adding a fourth element to the mix: the chemical chain reaction. The fire tetrahedron represents the addition of a component in the chemical chain reaction to the already existing three components (heat, fuel, and oxidizer) in the fire triangle. It mainly consists of the presence of a sufficient amount of free radicals.
Combustion is the chemical reaction that feeds a fire more heat, which allows it to continue. 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 removed.
The importance of understanding the fire tetrahedron lies in developing more effective strategies for preventing and extinguishing fires, especially for wildfires where free radicals contribute to an uncontrollable fire. Free radicals can create intense heat by reacting with available fuel sources, and quickly spread the fire to nearby dry foliage.
Extinguishing a Fire
Extinguishing a fire requires the removal of one or more elements of the fire triangle. The most common methods are using fire extinguishers, water, or simply removing the fuel or oxygen sources.
Fire extinguishers work by removing one or more elements of the fire triangle. For example, dry powder fire extinguishers contain a dry chemical powder that interrupts the chemical reaction of the fire by either creating a barrier between the fuel and oxygen that smothers the fire. With the right fire extinguisher, most fires can be extinguished relatively quickly, making them a valuable tool to have on hand.
In the case of some fires, water is an effective extinguishing agent. Water works by cooling the fuel source, reducing the heat necessary for ignition. As the fuel cools, the fire becomes less intense, until it finally can’t sustain itself. However, in some cases, using water can actually make the fire worse or can be very dangerous, especially when dealing with cooking oil fires or electrical fires.
Removing the oxygen or fuel source is another effective way to put out a fire. This is why smothering a campfire with dirt or sand works so effectively. This is the principle applied when using a fire blanket. Once the fuel source is cut off from the oxygen source, the fire can no longer sustain itself and will slowly die out.
It’s essential to remember that each fire is different, and the best way to extinguish it may vary. In some cases, using water may make the fire worse, while in other cases, removing the oxygen source could be more effective than using a fire extinguisher. Understanding the fire triangle and the different ways to combat fire is essential to prevent tragedies.
All firefighting agents seek to remove at least one side of the triangle. Water-based agents remove the heat from the fire. Powder and gaseous agents dispel the oxygen and suffocate the fire. Aerosol agents attack the free radicals and starve the fire of fuel.
Here at Blazequel – The Fire Protection Specialist, we employ advanced systems such as Water Mist Suppression systems which primarily removes the heat but due to processes during discharge, the volume of steam produced dispels the oxygen from the area. This removes two sides of the Fire Triangle and reduces the possibility of re-ignition, ensuring complete extinguishment and making this system extremely effective.
Let our expert fire service and consulting team ignite your path to greater safety and peace of mind. Contact us today to discuss your fire prevention, training, and emergency response needs at 01234 357357 or email sales@blazequel.com .
FAQ
What is Free Radical?
Free radicals form the basis of fire. When a material warms, molecules vibrate from side to side. As they do so, some break away from the main body of material. These are what is known as Free Radicals.
Due to now increased surface area of the material, sufficient oxygen can reach the free radical for combustion. Providing the temperature is high enough, an exothermic reaction ensues which emits radiation in the visible light band. This is what we call flame.
This exothermic reaction further increases the heat in the area, causing the molecules in the body of material to vibrate even more, thereby emitting more free
