| Science - Introduction | | How Heat Moves | | Flashovers | | Smoke |

When you think of fire you probably just think it is a flame that is hot and burns stuff up. There is more to fire than that. Fire is uncontrolled burning. Burning, or combustion, is the chemical reaction between a fuel and oxygen.

Burning can occur two different ways. The first way is usually the most preferred way. It is controlled and is used for our benefit. This type of burning can produce heat from a woodstove or fireplace, light from our electric lights, a way to cook on our stove and in our oven, and many more things. The second way is uncontrolled and is the type we want to prevent. It causes forest fire, house fires, conflagrations, and explosions.

When burning happens slowly, and without flames, it is usually called smoldering. When this happens very quickly, like when there is a gas leak that mixes with the air, we sometimes get an explosion. In between these two speeds of burning we have flames and fire. For fire to burn continually it must have, fuel, oxygen, heat, and chemical reactions. If one of these four things is not available then the fire goes out.

All fires start with ignition. Three things are needed in order to have a successful ignition. There must be enough heat to give the right amount of energy for the chemical reaction to start, there has to be just the right amount of fuel vapor in the air, and there has to be enough air. The following paragraph explains the way ignition works so well that I am just going to let you read it instead of trying to explain it myself.

"If there is insufficient energy, the molecules do not react with each other. The energy to cause ignition might be in the form of the heat from a match or a spark or a cigarette. The energy makes the molecules of fuel and of oxygen nearby move faster. This energy is called kinetic energy. If they move fast enough, they will react when they collide. If they do not move fast enough they will bounce off each other when they collide." This paragraph was quoted from Fire Engineering - Fire Science.

Different kinds of fuels take different amounts of energy to ignite. It is also easier to ignite something that has a lot of surface area. A pile of sticks is easier to ignite than a log because it has so much more surface area.

The speed a fire can grow depends on what type of fuel it is burning and how much air can get to the fire. When a fire is burning liquid and gasses it can grow very fast. Some solid materials burn quickly, too. Thin curtains or cloth burns quickly but thicker things like a stack of paper or something burns a lot slower.

There are a few ways we can put fires out when they start. Remember the four things a fire needs in order to burn? If we take away any one of those four things the fire will go out. If you take away the fuel the fire has nothing to burn. You can take away the heat by throwing water on the fire. That is the most common way to put out a fire. You can take the oxygen away from the fire by putting dirt on the fire. That smothers the fire. When a fire starts in your home don't try to put it out alone. Call the fire department immeditly.

| Science - Introduction | | How Heat Moves | | Flashovers | | Smoke |