Whether it occurs in the workplace, home, or elsewhere, it is difficult to overstate the unique and serious dangers fire poses to people, assets, equipment, and physical structures. A burning fire is a fascinating chemical chain reaction, and extinguishing a fire is a matter of disrupting that chain reaction. The better you understand how a fire starts—including the basic science of what components are required for it to ignite and burn—you’ll be better prepared when you need to extinguish a fire.
In this blog, we’ll break down the four components of a fire, and offer a few tips for better fire prevention and suppression.
How Does a Fire Start?
A fire starts when all three elements of what’s known as the “fire triangle”—heat, oxygen, and a fuel source—are present in the right conditions to create the fourth component, the fire itself. The fire itself is the combustion, an ongoing chemical chain reaction that continues to burn and grow until at least one of the three elements of the fire triangle is removed.
What Are the Three Elements of the Fire Triangle?
The three elements of the classic fire triangle are heat, oxygen, and fuel. Once the fuel reaches its ignition point (via heat), it reacts with oxygen in the surrounding air, causing combustion. Once a fire ignites, it will continue to burn until at least one of the three elements runs out.
The Fuel’s Role
When it comes to fuel for a fire, the first thing that comes to mind is probably a liquid accelerant, like gasoline or lighter fluid. However, fuels can actually be flammable solids, liquids, or gases. Technically, any substance that can combust can serve as the fuel for a fire. Since its fuel that burns, removing that fuel or the fuel running out, will cause the fire to die.
The Heat’s Role
How much heat is required for the chemical reaction depends on the fuel’s specific flash point—the lowest temperature at which the fuel will ignite. Heat can come from a number of different sources, and it doesn’t take a whole lot. For example, when you strike a match, the friction between the match’s head and the matchbook releases sufficient heat to light the match. When a fire is extinguished with a fire suppression chemical clean agent or water, it works by lowering the fuel temperature.
The Oxygen’s Role
A fire typically needs a constant supply of oxygen to ignite and burn. Considering just over one-fifth (21%) of the Earth’s atmosphere is oxygen, you can see why major fires (like wildfires) can burn and spread for days if not weeks or months, in some cases. Fire blankets and extinguishers are designed to quickly put out fires by cutting off the fuel from the supply of oxygen.
Why does a fire need oxygen?
Fire is the chemical reaction resulting from igniting a fuel source. The chemical processes behind fire simply can’t occur without oxygen being present—as a matter of chemistry. Basically, as fuel begins to burn, it reacts with the surrounding oxygen. This process, oxidation, releases heat as well as combustion products, like smoke or other gases. As long as the oxygen doesn’t run out, the fire continues to be fed. Other fire suppression agents work by lowering the oxygen concentration. For example, CO2 mainly does oxygen reduction and some heat removal while other inert gases are mainly oxygen concentration lowering
What Is the Fire Tetrahedron?
While the fire triangle is technically accurate in labeling heat, oxygen, and fuel as the three elements required for fire, a more advanced understanding incorporates a fourth element, transforming the fire triangle into the fire tetrahedron.
What Are the Four Components of the Fire Tetrahedron?
In addition to the three elements of the fire triangle, the fire tetrahedron includes a fourth element—a chemical chain reaction—as well. Adding this dimension gives a fuller picture of what causes fires to ignite and burn over time.
What Is the Role of Chemical Chain Reaction In the Fire Tetrahedron?
This chemical chain reaction keeps the fire burning by providing adequate heat to sustain the fire. As long as the chemical chain reaction is sustained, the fire will grow and continue to burn. When a fire is effectively suppressed, it is because at least one element of the fire tetrahedron—the ongoing reaction—has been removed from the equation.
How Do You Stop Combustion and Extinguish a Fire?
Stopping combustion requires depriving the fire of one or more sides of the fire triangle, or by stopping the chemical chain reaction that sustains combustion—and that’s how standard fire extinguishing work. It’s important to use the right type of agent to extinguish the fire, so we have created an overview of how the most common types of agents work to disrupt the fire triangle/tetrahedron.
- Carbon dioxide (CO2) and inert gases put out Class B and C fires by removing oxygen from the fire triangle. While inert gases will also put out Class A fires, CO2 can be used for surface Class A fires only.
- Water-based systems put out Class A fires by removing heat from the fire triangle.
- Dry powders are available in a few different types, with different applications appropriate for Class A, B, or C fires, work by applying a thin layer of material to separate the fuel from surrounding oxygen, interrupting the chemical chain reaction that keeps a fire going.
- Clean agents are highly effective against Class A, B, and C fires and disrupts the fire triangle by reducing the heat or separating the oxygen.
How Do You Extinguish a Fire Without Water or a Standard Fire Extinguisher?
In certain occupied or otherwise sensitive areas or equipment, it’s not always ideal to use water or a conventional-type fire extinguisher to put out a fire. The alternative is to utilize a clean agent fire suppression system, which requires no cleanup after discharge and poses no significant risk to equipment, people, or the environment. Clean agent fire suppression systems are suitable for use around equipment and assets, including precision machines, server rooms, electrical cabinets, data storage, and telecommunications systems, repositories holding records or files, artwork, and so on.
When it comes to protecting equipment, a key factor to understand is what class of fire may occur. As mentioned above, not all agents are effective for every class of fire. When selecting an ideal fire suppression agent and system, it is just as important to understand which class of fire you are protecting against.