756 
Journal of Agricultural Research 
Vol. XXX, No. 8 
A.-AREAS SUBJECT TO GENERAL RISK 
Unit 
F orest 
type 
Hour control 
Age Risk 
class class Less . 0 
! than hours Etc - 
j , hour , (acres) (acres) 
(acres) vaueb ' 
Quantity and 
value of 
timber and Gen- Total 
young growth end genera] 
x. A.. Ira- 
Total 
Per S 
acre 
! i I 
“General liability factors” are the 
factors for total liability per 1,000 acres, 
as already given in Table XII. With 
the data so far available there will be one 
uniform factor for each type in a given 
region, regardless of its age or risk class, 
but varying with hour control. When 
more detailed ratings can be made, it 
will be desirable to use different liability 
factors for stands of different ages and 
different relative risk. It will also be 
desirable to take into account the dif¬ 
ferences in quantities and values at 
stake, possibly by expressing liability 
of loss in terms of percentage of total 
values, instead of directly in dollars. 
The preliminary reconnaissance need 
not show age classes or risk classes, 
3. Special information should be 
given regarding areas of high liability, 
whether due to probability of occur¬ 
rence of fires, to probability of rapid 
spread and of difficulty in suppression, 
or to probability of heavy damage be¬ 
cause of the size of the area likely to 
burn over, or because of high destructi¬ 
ble values. Such information should 
describe the reasons for the high lia¬ 
bility, and, if possible, suggest means 
of reducing it. 
SPECIFICATIONS FOR CLASSIFYING 
RISKS 
The following specifications are sug¬ 
gested as a basis for the classification 
B.—AREAS SUBJECT TO SPECIAL RISKS 
Number of fires per year per unit area of the type, for the given unit and cause a 
1 Total 
Special special 
liability liability 
factor (for this 
cause) 
° The same data for each kind of special risk separately, as in A, except for the last two columns, for which 
should be substituted the last two columns of B. 
since we have not the data necessary 
to rate them separately. It is obvious, 
however, that both costs of suppression 
and amounts of damage will vary rather 
widely with differences in age or risk 
class within a single type, and separate 
ratings should be made as soon as fire 
records with the necessary basic in¬ 
formation accumulate. It is desirable 
to have information regarding the dis¬ 
tribution of age classes and risk classes 
for use in planning protection, even 
though we can not yet rate liabilities 
in such detail. The classification as to 
hour control should be based on what 
is reasonably possible with the existing 
or proposed protective organization, 
taking into consideration location of 
personnel and means and speed of 
travel. 
of areas indicated in the maps and 
tables described above. The limit of 
subdivision should be approximately 
40 acres for the intensive survey, or 
160 acres for an extensive one; or, in 
other words, no area should be dis¬ 
tinguished on the map, or counted in 
preparing the tables, unless it is at least 
40 or 160 acres, respectively, in extent. 
Smaller areas should be thrown with the 
neighboring ones. Exceptions to this 
rule may be made in the case of smaller 
areas of especially great liability. 
Forest types. —To be classified on 
the basis of present cover, because that 
is what is being protected and what de¬ 
termines the hazard and liability. All 
areas which are fairly satisfactorily 
stocked with tree growth, no matter 
how small, should be classed with the 
