In this lesson, we're going to learn some ways that fire behaves so we can understand the fire triangle. This will require some matches, a candle, and of course, an adult to help or watch. Before you begin, take a moment to think about what you can do to make sure that your're safe while using fire? That's right - make sure there is nothing around you that can burn (on the table, curtains that are hanging, wall hangings, etc.). Also, make sure that your clothing isn't loose or flopping around, and that you have a safe place to put something burning (a metal ashtray or ceramic dish). I'm also going to be careful not to knock over the candle.
So what is the Fire Triangle? The three sides of the fire triangle are fuel, heat and oxygen. These are the three things a fire needs to burn. But it first needs to have an IGNITION to start it. When you strike a match, what happens? The friction produces enough heat so that the match starts to burn. The fuel is the match-head and matchstick, with enough heat, and the oxygen is keeping a chain reaction going. The three elements of the triangle - fuel, heat and oxygen - all have to be there, or the chain reaction is broken and the fire goes out. What happens if you put a lighted match into an ashtray (something that isn't flammable)? Which side of the fire triangle will break? It has plenty of oxygen from the air. It is still hot - we haven't cooled it off by putting it down. What happens? The match is small and it is the only fuel. When the fuel has all been burned or has COMBUSTED there is no more fuel, so the fire goes out. You can demonstrate cooling the match by dipping it in water or blowing on it.
When you watch an lighted candle you can see the flame. What colors do you see? If you put your hand a few inches over the flame, does it get hot? Do you see the whole flame? We can't see the gases at the top of the flame - they are invisible to our eyes. But we can feel the heat RADIATING from the flame gases. Radiant heat can be enough to ignite a fuel that is close enough.
Why is the flame bigger on a candle than on a match? More fuel means more flame and more heat being generated. Why does a flame keep burning? It's a chain reaction - the flame is heating the fuel, and the fuel is feeding the flame. There's plenty of oxygen. But we can break the triangle by putting a container over the candle. Which side of the triangle would we break? That's right - oxygen.
Grab a piece of paper. This is what we would call a fine fuel. It's light, dry, and will burn quickly. Next, grab a hold of a phone book. Drop it on the floor if you like. How about the phone book? What do you think? Will it burn as quickly as the single sheet of paper? Why not? It's because the phone book is a heavy fuel. Radiant heat might ignite it but it will take longer to burn through more fuel. The fuel also is densely packed so there is not a lot of oxygen (unlike crumpled pieces of newspaper you might use to start a campfire). But it can catch fire if there is enough heat, especially if something burning (like coals) were sitting on it for a while. In a wildfire, trees and bushes burn and create something we call EMBERS or FIREBRANDS. They are like little pieces of charcoal you would use in a barbecue, but they fly in the wind and can land in your yard, on your deck, or your roof and slowly burn anything flammable. There are lots and lots of them during a big wildfire, and they will pile up like snow.
What can we do to keep wildfires from burning our homes? Which sides of the triangle can we control? Oxygen? We can't we drop a giant pan lid on the wildfire! Heat? Can we control how cool it gets or whether it rains? No. We could put water on the fire but in a really big wildfire there isn't enough water to go around. And often it's very hard for fire fighters to get close enough to bring the water in without getting hurt. We could wet down our yards and walls and roofs but it might not be safe enough for us to stay near our homes during a really big wildfire.
So the answer must be...fuel! What can we do about fuel? Get rid of those fine fuels (like the sheet of paper) around the house. What are some fine fuels around the house or on the house? Pine needles, dry grass, and dry leaves are just a few. If you've ever made a campfire, you start with fine fuels for kindling. Look for things you could start a campfire with--these are the fine fuels that can allow a wildfire to spread to your home or community.