What is Fire?

Fire is the rapid oxidation of material in the exothermic chemical process of combustion, releasing heat, light and other reaction products. It is a self-perpetuating chemical reaction that will continue as long as there is fuel and oxygen. The burning fuel vaporizes, releasing gases that ignite the flame to keep it going. The heat of the flame keeps the remaining fuel at its ignition temperature and it vaporizes other nearby fuel as well, causing it to burn, and so on. A fire is often characterized by its colour: hotter fuels emit brighter colours, such as red and yellow, while cooler fuels produce less intense or even colourless flames.

Fire can be caused by both deliberate human action and by accidents or natural processes. Humans have learned to use fire to cook food, clear land and furnish warmth in caves or hovels, hunt game and destroy disease-causing organisms. It is also used in industrial settings to produce electricity, for welding metal and other purposes.

The chemical reactions of burning fuels produce heat energy, which is transferred from the atoms of the fuel to the surrounding air molecules, which become excited by the fusion and rearrangement of their electrons, making them vibrate faster. This vibration is what produces the visible light of a fire. The vaporized fuel gases also produce carbon dioxide, which is expelled into the atmosphere. Incomplete combustion can result in smoke, which is produced as the gases are released.

What makes fire a dangerous and destructive phenomenon is that it can easily go out of control. If the fuel supply runs out or if the fire can no longer re-ignite, it will eventually diminish to nothing. When a fire is out of control, the hot and glowing embers can fall on people or property, resulting in burns or explosions.

Some fuels are not combustible without the presence of some kind of oxidizer, such as oxygen gas or another compound that is rich in oxygen. Other fuels are not combustible until heated to a high enough temperature. Once the fuel reaches its “ignition point,” the oxidizer can quickly combine with it to form a chain reaction, causing the fuel to burn and emit gases, including the characteristic flames of fire. This combination of elements, called the fire triangle or fire tetrahedron, is what makes it possible to create a fire.

The conditions for the formation of a fire are controlled by the type of fuel and its moisture content, the ambient air temperature and the wind. Wind influences both the rate of combustion by heating the fuel to its ignition temperature and by blowing unburnt fuels away from the flames (controlling combustion). In addition, wind can dry out fuels or carry combustible materials from one area to another. These are all factors that can contribute to wildfires, which occur whenever a natural ecosystem has been disrupted and moved into a different state than it was in before.