Apr. 15, 1925 
Use of Liability Ratings in Forest Fire Protection 
745 
To use these figures in estimating the 
general liability of a given forest unit 
it will be necessary to know the area 
and location of the different types of 
forest cover within the unit, and the 
hour-control that will be effected for 
all parts of the unit with the existing or 
proposed protective organization. 
Thus, the fire plan might show a forest 
in western Montana something like this: 
the fixed risks and varies for different 
units as the chance of occurrence of 
fires varies. In order to rate a unit it 
will be necessary to know what areas 
of each type are exposed to special risks, 
how many fires per year can be expected 
in each, and what hour control will be 
provided by the existing or proposed 
protection organization. The number 
of fires per year will be based on the 
J 
Forest type Area 
Hour control 
General 
liability 
Acres 
Western yellow pine_ 100,000 
Hours 
Less than 1_ 
Dollars 
79.00 
116. 50 
151. 00 
182. 50 
42.50 
157. 00 
414. 00 
204. 00 
59. 00 
59.50 
21.00 
42.00 
! 50,000 
50,000 
50,000 
Douglas fir_ _ 50,000 
2_ 
3 _ . 
4_ 
2 
100,000 
200,000 
50,000 
Lodgepole pine_ 100,000 
4_ 
6_ 
12 
6_ 
50; 000 
Subalpine_ _ 50,000 
8 _ 
10 
| 50; 000 
15_ 
Total general liability for the forest_ _ ! 
1, 528. 00 
r. I t * 
This means that, with the given 
amount of protection, the average an¬ 
nual loss plus suppression cost for gen¬ 
eral risk fires, for a period of years, 
ought to be about $1,500; some years 
might run above, others below this 
figure. It is hardly necessary to say 
that the example given is for a purely 
imaginary forest. 
Special Liability. —Rating of the 
special liability will be done in a slightly 
different way. It is not uniform for the 
whole area of a given type within a 
region, but is confined only to those 
parts of the type which are exposed to 
average number which have occurred 
in that particular unit during a period 
of years, making due allowance for 
changes in the hazard, such as adop¬ 
tion of spark arresters or of fuel oil, or 
construction of effective fire lines along 
railroads. The special liability will then 
be the products of losses plus costs 
per fire for different hour control peri¬ 
ods, found in the same way as described 
under general liability, multiplied by the 
number of special risk fires. For example, 
let us take the hypothetical western for¬ 
est already described. We find that areas 
exposed to special risks are as follows: 
1 
| FivpQ 
Class of risk, forest type, and area ! Hour control 
i pvl j vdl 
Loss 
plus cost 
per fire 
Product 
Railroad fires: 
Yellow pine type— Hours Number 
50,000 acres_ Less than 1_ 25 
20,000 acres__ 2_ 10 
Douglas fir type- 
20,000 acres_& 2_ 5 
Dollars 
25. 25 
74. 50 
83. 60 
Dollars 
631. 25 
745. 00 
418.00 
Total liability due to railroad - - ______ 
1, 794. 25 
Lumbering operations: 
Yellow pine type- 
25,000 acres_ Less than 1_ 8 
Douglas fir type- 
50,000 acres_ _ 2 _ _ 7 
25. 25 
83. 60 
202. 00 
585. 20 
Total liability due to lumbering__ 
787. 20 
Total special liability_!_ _ 
1 : 
_ ! 2,581.45 
