How Fire Works

Fire is a chemical reaction that releases heat and light energy. It can burn many different types of fuels, such as wood or oil. When burning, these fuels combine with oxygen from the air to form water and carbon dioxide. The release of carbon dioxide makes the air seem smoky, which is why we use fire to cook our food and keep it hot.

Besides producing heat and light, fire is also useful in destroying harmful organisms. It is also a valuable tool in reducing the buildup of dead plants, which could choke out the growth of new vegetation. It can help clear the way for plants to access nutrients in the soil, which allows them to grow faster. In this sense, a fire is like a natural fertilizer.

The way a fire spreads depends on what type of fuel it is made of. Some fuels have a very low moisture content, which means that they burn quickly. Other fuels, such as coal or petroleum, require a lot of oxygen to ignite and burn.

When fuels are exposed to heat, they react with oxygen in the air and produce gases, which make the flame look brighter. Some fuels, such as gasoline, burn quickly, resulting in very little char. To get the best results from these fuels, people often start a fire with kindling (small pieces of wood) that they criss-cross to increase surface area and allow for lots of oxygen contact.

As the flame heats the surrounding fuel, it ignites any gases released, which spreads the fire. The heat from the flame also keeps remaining fuel at its ignition temperature, causing it to continue burning. Eventually the available fuel runs out and the fire dies.

Several factors affect the behavior of wildfires, including terrain and weather. Steep slopes preheat fuels through convection and radiation, which increases the speed at which a fire spreads. If the weather is windy, it may carry the fire in a particular direction or sweep it from one side to the other.

In addition, the way a fuel consists of compounds and how much oxygen it contains can affect how fast it burns. Some fuels, such as petroleum, burn slowly because they consist of a mix of compounds that react with oxygen differently. Others, such as wood, burn quickly because they are a mix of simpler compounds that burn more easily.

Another factor affecting fire is the amount of fuel it has and how dry it is. A large amount of fuel in a very dry state can burn very rapidly, even though it may not be particularly hot. Conversely, a small amount of fuel in a moist or wet state will burn slowly. A well-planned burn, such as that performed by humans, can be used to accomplish specific management goals for an area of land. This type of fire is called a prescribed burn. The goal of a prescribed burn is to reduce the amount of organic matter that builds up on the ground and prevents other vegetation from growing.