What Happens When a Fire Starts?

A hypnotic, primal force, fire is a fascinating and powerful phenomenon. Its flickering light, crackling sounds, and distinctive smell have a relaxing effect that may be rooted in evolution—prehistoric campfires offered protection, warmth, food, and social cohesion for hunter-gatherers.

When a fire starts, it’s because of a chemical reaction called combustion that turns fuel into gases and heat. The heat breaks apart carbon atoms and hydrogen molecules in the fuel, releasing energy in the form of light and heat. The atoms of the fuel are so hot that they glow, a process known as incandescence (you can try this at home with a candle). The color of the flame varies; the hottest parts of a fire glow blue, while cooler areas are orange or yellow.

Once the gaseous fuel is ignited, the heat from the atoms and molecules quickly breaks apart even more of the atoms, forming more gases. These gases then react with oxygen in the air to produce more flames and more heat. The resulting chain reaction is self-sustaining, so long as there is enough fuel and oxygen in the area.

The fire also releases some of its heat into the environment around it, causing it to warm up and dry out. This drying out of the soil increases its ability to absorb nutrients from organic matter, which is important for plant growth and ecosystem health. The cycle of burning and drying out of the land is sometimes referred to as a “fire regime,” and humans can intentionally create this cycle in a controlled way to accomplish management goals for the landscape. This is known as a prescribed burn.

While it may seem counterintuitive that a phenomenon such as fire, which destroys plant life and endangers animals within an ecosystem, can promote ecological health, periodic wildfires are vital to many ecosystems. For example, dead or dying plants and animals can build up on the ground to the point where they prevent other organisms in the soil from accessing essential nutrients. When the dead material is burned in a controlled setting, such as a prescribed burn, it allows these other organisms to thrive and provides fresh nutrients for new plants to grow.

Fire has other uses as well, including a source of light and heat for cooking, heating, and signaling. The light emitted from the burning of wood and other materials is used in street lamps, car headlights, flashlights, and candles. It is also used to provide light for astronomical observations.

It might seem surprising that a natural phenomena such as fire could cause harm to the environment, but this is because we are not used to seeing it in its natural state. Unless we control the ignition of fuel and the release of oxygen, fire can be a dangerous force to be reckoned with. For this reason, it is important to follow Smokey’s ABCs: Always Be Careful with Fire!