Forest Fire Danger 



U. S. Deportment of Agriculture 



Forest Service 



Southeastern Forest Experiment Station 



Asheville, N. C. 



Meter Type 5-W 

 July 1,1947 



used to weigh the sticks to detect 

 changes in moisture accurately. The 

 measurements are integrated by a de- 

 vice called a fire-danger meter into a 

 single numerical rating. In the eastern 

 part of the United States, five danger 

 classes are recognized, in which class 1 

 represents the lowest, and class 5 the 

 highest. 



Although the discussion to follow is 

 based on these classes, the meter has 

 recently been converted to one with 

 100 classes. The conversion permits 

 more detailed expression of gradations 

 in fire danger and a more precise 

 evaluation of it. The chart illustrates 



how this new danger meter works, and 

 shows the relation between the five 

 danger classes and the newer 100-class 

 scale. 



A scale of fire danger is much like 

 the Fahrenheit scale of temperature. 

 Many phenomena are related to tem- 

 perature, such as the freezing and boil- 

 ing points of water and the melting 

 points of the different metals. Likewise, 

 many of the most significant fire phe- 

 nomena are related to fire danger : The 

 likelihood that fires will start, their rate 

 of spread, the cost of suppression, the 

 damage they cause, and the amount of 

 work needed to suppress them. Rec- 



