Fire Fundamentals - The 3 Fire Triangle Elements! (2024) - FFG (2024)

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Fire can’t exist without the three fire triangle elements. We, humans, have an extraordinarily long relationship with fire. For one, fire has both life-giving and life-taking powers. Sometimes we crave it for cooking and warmth but cannot have it. Other times it swallows our homes and lives.

Fires can be deadly and incredibly difficult. However, you can control the fire by reducing or eliminating only one of these three elements.

Therefore, knowing the three elements of fire enables us to learn how to control the fire to light it, keep it lit, and put it out on our terms.

What are the Fire Triangle Elements?

The fire triangle is a model that demonstrates the three elements required for a fire.

The three elements of the fire triangle are:

• Oxygen
• Heat
• Fuel

Every fire triangle element is required for a flame to start and continue burning.

The Fire Tetrahedron

Sometimes we call the fire triangle a ‘fire tetrahedron.’

A tetrahedron is a 3D fire triangle. The extra point in the tetrahedron is the ‘chemical reaction’ (combustion) that occurs when the three elements of the fire triangle are present in enough quantity.

A chemical reaction (precisely an “exothermic” reaction) constantly occurs during a fire. The effects of this chemical reaction are the heat and light that we see as ‘fire.’ The stored energy in the fuel reacts with the oxygen and heat to let off excess heat and light.

Review each of the Three Fire Triangle Elements

Quick Review: The three fire triangle elements are oxygen, heat, and fuel.

1. Oxygen

In most situations, you require oxygen to create combustion (the fire’s chemical reaction). In most cases, this is simply the oxygen in the air.

So, the air in our atmosphere is a good source of oxygen for fires to take off.

During large wildfires, the fire extracts oxygen out of the air at an incredible rate. As a result, firefighters often report a sense that they cannot breathe when stuck in raging fires.

In exceptional circ*mstances, one can use elements other than oxygen to start a fire. We call these elements ‘oxidizers’ or oxidizing agents.

Oxidizing agents can create the same chemical reaction as oxygen during a fire. That chemical reaction involves the transfer of oxygen atoms or electrons, which causes the chemical reaction in a fire known as combustion.

We often use oxidizing agents when oxygen in the atmosphere is not present, such as in space. For example, spaceships must carry their oxidizing agents to cause their rockets to fire.

Another example of using an oxidizing agent to cause fires is NOS in drag racing cars. NOS (Nitrous oxide) is injected into a car’s engine to increase the concentrated amounts of oxygen present during combustion. This injection strengthens the engine’s combustion and forces the pistons to move faster than they usually would.

Here they are using NOS in theFast and Furious movie:

Common oxidizing agents include:

• Oxygen (O2)
• Ozone (O3)
• Nitrous oxide (N2O)
• Hydrogen peroxide (H2O2)
• Sulfuric acid (H2SO4)

2. Heat

Heat is required to start a fire. But, once the fire begins, it often generates enough heat to keep the fire going without needing to add continually.

There are three temperatures for a fuel that will demonstrate when combustion will occur:

1. Flashpoint: The temperature at which a substance will burn when exposed to an open flame (such as a match).
2. Autoignition temperature: The temperature at which a substance will burn without exposure to an open flame.
3. Fire point: The temperature at which a substance will continue to burn on its own after ignition (usually a few degrees higher than the flash point).

The heat needed to burn something is called the ‘autoignition temperature.’ This condition happens when enough vapor molecules are extracted from the fuel to cause the fuel and oxygen to combust. It’s where oxygen atoms or electrons transfer between the oxygen and fuel source, and the stored energy releases energy, heat, and light (e.g., a fire).

Depending on the material, the heat transfer will be faster or slower. That is the reason why some materials can withstand fire better than others.

The ‘flash point‘ is another temperature at which combustion may occur. However, this is the temperature at which something will burn if exposed to an open flame, like a match. It’s lower than the substance’s autoignition temperature.

The ‘fire point‘ is the heat point at which combustion will self-sustain for at least 5 seconds without needing more heat. This point is usually a few degrees above the flashpoint of the fuel source.

Here are the flashpoints and autoignition temperatures of usual fuel sources:

For more, see https://www.engineeringtoolbox.com/fuels-ignition-temperatures-d_171.html.

When we rub sticks together to light a fire, we generate heat through friction.

3. Fuel

The third and final fire triangle element is fuel, which is the heart and soul of fire. It releases the stored energy in heat and light during combustion.

Fuels for fire are different from other forms of power, like batteries that release electrical energy or springs that release mechanical energy. In contrast, all these different types of fuels all release stored energy, while fuels for fire release them in the form of heat and light.

The traditional form of fuel for a fire is wood. Humans have controlled wood fuel for fires for more than 2 million years.

Since 800 BC, people have been using fossil fuels such as coal ever since Persian chemists used them. But it wasn’t until the Industrial Revolution in the 1700s that humanity used fossil fuels on a large scale. In this era, machines translated the stored energy in fire fuels into mechanical and electrical power through steam and combustion engines.

Standard fuels for fires include:

How hot is fire? To what temperature can fire get?

The fire’s temperature depends on the fuel type, amount, and available oxygen or oxidizing agent. If you want a broad temperature range for your average fire, it can go between 400°F (200°C) and 9000°F (4,982°C).

Estimating the fire temperature is done by looking at the flame’s colors. Check this article for a full in-depth view of this subject!

Of course, it depends on the material burning (fuel). However, given standard burning conditions, an estimated range based on colors would be:

• Blue Flame: the hottest of them all, blue flames can get from a 2,732°F (1,500°C) to a mighty 5,432 °F (3,000°C). Not many elements can withstand this heat intensity.
• White flame: not signifying purity at all in this context, white flames can range between 2,372°F (1300°C) to 2,732°F (1,500°C)
• Orange flame: on this flame level, temperatures oscillate between 2,012 (1,100°C) and 2,372°F (1300°C)
• Red flame: the most common color is red, especially during house fires. Red flames burn between 600 to 850 °C (1,112 to 1,562 °F).

Our friends at Nasa went a step further and analyzed a flame in microgravity. Their experiment demonstrated that in space, a normal candle fire is blue. This color is not because it runs hotter but because the missing gravity means that there are no convective flows and therefore burns without soot.

Nasa microgravity experiment

Implications for Fire Control

Quick Review: Fires need all three elements in the fire triangle to burn. The fire will dwindle or extinguish if one of the three elements diminishes.

The fire triangle is a model for firefighters to conceive ways to extinguish fires out of control.

Most firefighting and fire extinguishing equipment strive to minimize one of the three elements of a fire.

Here are some examples:

1. Backburning

To reduce the element of fuel.

Firefighters can often put it out when a wildfire is out of control. However, the fire has too much heat, oxygen, and fuel, so it will keep going. We don’t have the tools to extinguish the fire.

Backburning is a strategy that involves moving ahead of the fire and removing the fuels that are in the fire’s path. Usually, this will include running controlled burns ahead of the central fire to burn away any potential fuels for the primary fire. Firefighters extinguish these smaller fires before the primary and out-of-control one arrives.

When the fire arrives, it finds no fuel to burn, so it stops.

An alternative to backburning is bulldozing trees in a strip of land and carrying them away, creating a gap in the forest that the primary fire cannot leap.

2. Water

To reduce the element of oxygen.

Water from a fire fighting pump or sprinkler can smother a fire to reduce its access to oxygen.

Similarly, suppose you plunge a burning log into a river. In that case, the water will extinguish it because its access to the oxygen in the atmosphere gets cut off.

Water can lower the temperature of a fire, helping us to bring it under control.

Fire extinguishers that use water, also known as Air-Pressurized water Extinguishers, are not very common. However, contrary to popular belief, water is not good at lighting a fire.

Here are some issues with water extinguishers:

• Water will often run off a fuel source, so it does not suppress oxygen access for all that long.
• Grease floats on top of the water for grease fires, so the fire will continue to burn ‘on the water.
• For electrical fires, water is an electrical conduit. So the water will become electrified and can cause severe electrocution of the firefighters.

3. Sand / Soil

To reduce the element of oxygen.

You’ll often throw sand and soil over the fire when you put out a campfire. By effectively burying the fire, you’re depriving it of access to the oxygen in the atmosphere, causing it to extinguish. However, the fire could burn for a while after being buried. Therefore it’s an excellent recommendation to continue to monitor the fire even after covering it.

4. Fire Extinguisher

To reduce the element of oxygen.

The fire extinguisher you will find lying around your home will probably be an ABC fire extinguisher.

These extinguishers put out the most common household fires – Class A, Class B, and Class C. In addition, they put out the trash, wood, and paper fires (Class A), liquid and gas fires (Class B), and energized electrical fires (Class C).

An ABC fire extinguisher works by shooting out a dry chemical called mono ammonium phosphate. This chemical smothers a fire and deprives it of oxygen.

5. Fire Blanket

To reduce the element of oxygen.

A fire blanket smothers a fire source and is excellent for small house fires. Therefore, I wholeheartedly recommend you keep some in your house at critical locations. The main component of fire blankets are woven glass fiber fabrics that are highly fire-resistant, and air doesn’t pass through them.

When the fire blanket is thrown correctly over the whole fire, it will create a barrier between the fire and the oxygen, putting it out.

It works similarly to when you put a saucepan over a candle holder to put out a candle. You can see the candle splutter as it sucks up all the last little bits of oxygen under the saucer before it finally subsides.

FAQ

Conclusion

The fire triangle is a great model for learning what a fire needs to burn. A complicated mix of different fuels might determine how strongly a fire burns. However, there are only three requirements at its core: oxygen, energy, and heat.

This model helps us think about what we need to start and extinguish a fire. All modern firefighting methods deprive a fire of at least one of the fire triangle elements.