FUNDAMENTALS OF FIRE BEHAVIOR.

There are only three things you can do to stop a fire-rob it of its fuel, keep it from being heated to the ignition point, or shut oil' the oxygen supply. When it comes to lire behavior, there are likewise only a few basic variables. The big one is fuel moisture, and when our fuel moisture indicator sticks are below 5 percent you can expect your tires to blow up and explode. As that moisture content rises above 5 percent your tires become less and less explosive and you know that they are then more and more influenced by another major variable, wind. Both fuel moisture and wind are measured every day of the tire season at numerous stations. Those measurements will show you clearly and accurately what the present moistures and velocities are, and how they are changing, whether getting better or worse. These are facts. They are available to you. They were not available to the rangers and supervisors who thought the tires of 1910 and 1919, nor to many men in 1928 and 1929. You therefore have this accurate knowledge that those men did not have. Furthermore, you have some knowledge of how both fuel moisture and wind velocity differ according to altitude and aspect. The outstanding general differences are known. Very few if any of the most experienced old-time fire fighters knew these things. And finally you have not only excellent topographic maps to help you visualize your fire area, hut you have the major differences in fuel types shown clearly so that you can calculate what you should expect your tire to do on this particular slope in the next few hours. It is true that you still have to estimate how much different the fuel moisture will he at your tire from what it is at the tire danger station. You also may still have to guess what the exact wind direction and velocity will he on your tire even after you find out what they are at the nearest ranger and lookout station. [ABSTRACT FROM AUTHOR]

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