How wildfire fighting works
By Marshall Brain
http://www.JewishWorldReview.com | (MCT) If you have been watching firefighters battle the wildfires in California, you know that they are using many different technologies. Some of these technologies are as old as human intelligence, while others are brand new.
The most photographic of all the technologies involves airdrops. You have probably seen news footage of airplanes and helicopters dropping huge plumes of red fire retardant on the fires. What is the liquid, and why is it red?
A typical airplane to use is the C-130. Inside the C-130 are tanks that hold 3,000 gallons of liquid. It is possible to dump 3,000 gallons of normal water, but usually they add two things to the water when fighting a wildfire. The first is a red dye. The dye is handy because it leaves a big red mark on the ground to let the next pilot know which areas have already been hit.
The second is a product called Phos-Chek. It's what is known as a "Long-Term Fire Retardant". The two main ingredients in Phos-Chek are ammonium phosphate and diammonium sulfate, both of which are forms of fertilizer.
One advantage of Phos-Chek is the fact that it lasts. It creates a no-burn zone until it is washed off by a strong rain.
You may have also seen trucks covering houses in what looks like foam. In most cases it is actually a polymer gel made of sodium polyacrylate. This is the same chemical that you find in disposable diapers to absorb liquid and prevent leaks.
The polymer mixes with water to form a gel that coats the house and can last 12 to 24 hours. When the fire comes, it has to boil off all the water in the gel coating before it can light the house on fire. With a gel coating about a quarter of an inch thick, the fire is gone before all of the water in the gel evaporates, and the house is untouched by the fire.
NASA was also helping out this year, providing robotic airplanes with infrared cameras. The cameras can penetrate smoke to map out new fires and hot spots, making it easier to track the blaze as it develops.
There are also the old standbys. Bulldozers can cut firebreaks through fields and forests on level terrain. The basic idea here is to simply remove burnable material from the path of the fire so that the fire dies when it hits the firebreak. In remote areas and in hilly terrain, the bulldozers aren't available. It's up to human beings to build the firebreaks by hand.
The people who fight fires this way are called hotshots. It's a dangerous job. Hotshots work in teams and are often very close to the fire. For protection they wear fireproof Nomex shirts that are usually bright yellow to improve visibility. Using shovels, axes and chainsaws, hotshots create a firebreak. Hotshots use radios and GPS receivers to keep track of the fire, and helicopters drop drinking water and supplies.
Sometimes things get out of control. A change in wind direction can bring the fire right on top of a hotshot team. In that kind of situation, hotshots carry a piece of technology that they use as a last resort. It is a small tent-like structure called a fire shelter and it only weighs about half a pound. The key is a reflective aluminum foil shell that reflects the radiant heat of the blaze.
Even with all of this technology and manpower, a wildfire is still a powerful enemy with a mind of its own. As we saw this year, hundreds of thousands of acres can be consumed by a big fire before people can bring it under control.
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© 2007, How Stuff Works Inc. Distributed by McClatchy-Tribune Information Services.