It is fire season again in Arizona. We’ve already had some devastating fires up near Flagstaff, including the Schultz Fire which burned more than 15,000 acres. In fact, just this week, Flagstaff law enforcement had to deal with an additional THREE little fires. Officials are thinking arson…
Fires take up a lot of airtime on our summer news broadcasts: man-made fires, smoking restrictions, fire restrictions, wildfires, and really scary terms like: “defensible space”, percent contained, homes lost.
You all know how much I love s’mores (4 recipes in one cookbook!) and that I have written articles in the past about safe fire starting. But, one of the most important steps of the fire making process, I’ve only mentioned in passing. And, that’s the right way to put out a fire.
HOW FIRE WORKS
The Basic Elements of Fire
The word “fire” refers to the natural phenomenon that occurs whenever a combustible fuel comes into contact with oxygen at an extremely high temperature. Fire is the byproduct of a chemical reaction in which fuel stored in a combustible fuel is converted to a gas. A fire’s flame refers to the visual indication of light that occurs once the gas is heated, and is evidence that a fire has taken place.
Fires can be man made or natural. When lightning starts a fire in dry grass, it can be just as devastating as a campfire that gets away. A few summers ago, a wildfire in Arizona was actually started by a dust devil. The story goes that a dust devil scooped up a piece of tin, the tin hit a power line and gave off sparks. The sparks fell into dry grass and BANG! a fire was started.
The Fire Triangle
The Fire Triangle was developed by natural scientists as a simple way of understanding the factors of fire. Each side of the triangle represents one of the three ingredients of fire — oxygen, heat, and fuel — demonstrating the interdependence of these ingredients in creating and sustaining fire. Remove any of these three factors from the triangle, and a fire will die.
The interaction of the three equal sides of the fire triangle: heat, fuel and oxygen, are required for the creation and maintenance of any fire. When there is not enough heat generated to sustain the process, when the fuel is exhausted, removed, or isolated, or when oxygen supply is limited, then a side of the triangle is broken and the fire is suppressed.
A heat source is responsible for the initial ignition of wildland fire, and heat is also needed to maintain the fire and permit it to spread. Heat allows fire to spread by removing the moisture from nearby fuel, warming surrounding air, and preheating the fuel in its path, enabling it to travel with greater ease.
Matches, sparks, coals from a campfire not properly put out, a cigarette butt, etc are sources of heat.
Fuel could be defined as any kind of combustible material, and is characterized by its moisture content, size and shape, quantity, and the arrangement in which it is spread over the landscape. The moisture content of any fuel will determine how easily that fuel will burn.
In Arizona, the large number of dead pine trees (caused by drought and the pine beetle) are an easy source of fuel for a wildfire. Since it is still hot and dry here the moisture content is low. When it rains, even dead wood will have a moisture content, absorbed from the rain and the humidity in the air.
Slurry (the red stuff dropped from the planes in the case of a wildfire) is 85% water. It’s used to raise the moisture content and help stop fires.
Air contains about 21% oxygen, and most fires require at least 16% oxygen content to burn. Oxygen supports the chemical processes that occur during a wildland fire. When fuel burns, it reacts with oxygen from the surrounding air releasing heat and generating combustion products (i.e. gases, smoke, particles). This process is known as oxidation.
Make Sure it is Out!
1. Let the fire burn down as far as possible. This is why having a small fire is better than having a big fire. Don’t leave a fire unattended.
2. Pour water onto the fire and around the fire area. Use enough water to float the coals and totally soak the area. Roll back any rocks from around the fire and pour water in and around where they were. Be sure to put rocks back into the fire ring when you’re done.
Be prepared for ashes to kick up into your face so stand on the up-wind side and pour water on slowly, using a small stream of water. Don’t throw water on the fire since it can actually spread hot coals.
3. Stir the coals, ashes and dirt. At this stage, you’ll most likely need to add more water and then stir again.
4. Check the coals for heat with your bare hand when you think it is out to make sure there are no hot areas. If there are any hot areas, go back to step 2 and pour on more water!
Make putting the fire out one of the first things you do when breaking camp. Put it out well in advance, so you can watch it for some time before you leave. Make sure that no roots are burning. Do not bury your coals — they can smolder and break out.
Readers Weigh In:
- Have you had any experiences with a campfire that got away?
- Have you ever been traveling the back roads and needed to put out an unattended campfire?
- What tools do you carry with you to put out fires? (Shovel, water, etc)