Apr. 15, 1925 
Use of Liability Ratings in Forest Fire Protection 
753 
THE USE OF LIABILITY RATINGS 
IN EIRE PLANS 
It is realized that the figures given in 
Tables VI to XIII are based on such 
incomplete data in many cases, per 
haps in all, that they can not be used 
as absolute guides in allotting funds 
for primary protection. It does seem 
reasonable to believe, however, that 
figures worked out in this way can be 
so used, as soon as sufficient data 
accumulate to afford a basis for reliable 
figures on spread of fires, on suppression 
costs, and on the damage done in dif¬ 
ferent types. It will also be desirable, 
perhaps, to have a more detailed clas¬ 
sification of fires based not only on 
mere segregation by types, but also 
according to differences in the age of 
the stands, differences in quality of 
sites, and differences in characteristics 
with respect to inflammability. 
Meanwhile, the figures given here 
may serve as valuable indicators in 
planning protection, provided they are 
not relied upon to too great an extent. 
In the first place, as fire plans for each 
of the national forests are worked out, 
showing the locations and areas of the 
different forest types classified accord¬ 
ing to the hour control now in effect, 
and ratings are made by the use of the 
tables, great differences in liabilities 
between different forests will undoubt¬ 
edly appear. It will then be proper 
to examine more closely those forests 
whose liability is rated especially high 
and extremely low, to see whether or 
not more protection should be given 
the former. 
Then, if the ratings could be relied 
upon absolutely, the justification of a 
suggested increase or decrease in pro¬ 
tection could be determined by weigh¬ 
ing its cost against the reduction or 
increase in total liability effected by 
such modification of tire protection 
organization. Ratings based on the 
present data are not good enough to 
decide such questions, but should at 
any rate be suggestive. 
A point which should be borne in 
mind is that it may not always be 
necessary to increase expenditures in 
order to increase the intensity of pro¬ 
tection or to reduce the hour control. 
This may be accomplished on any 
forest unit in other ways, such as 
changing the distribution of personnel 
so as to locate men nearest to where the 
greatest number of fires will start, or 
nearest to where fires may be expected 
to spread most rapidly or be most 
destructive or costly to control, such as 
slashings, for instance. Nor do in¬ 
creased protection expenditures neces¬ 
sarily mean increased personnel, but 
the expenditure may be made in such 
a way as to reduce the hazard, by 
isolating special risks, or by removing 
especially hazardous conditions, such 
as logging slash, windfalls, or snags, or 
by improving communication. 
MINIMUM REQUIREMENTS 
It is believed that one exception 
should be made to the general principle 
of weighing costs against liabilities; 
that is, except in a very few places 
where it is certain that fires can be left 
without danger, enough protection 
should be provided during the danger 
season so that it will be possible to 
reach any part of every forest unit 
within 12 hours after a fire is discovered. 
The reason for this is that the law of 
averages is less dependable for longer 
elapsed periods, and even though 
averages may show comparatively low 
liabilities, it is more than likely that a 
considerable proportion of fires left 
for longer periods may do a great deal 
of damage or may prove very costly 
to control, or that they will spread 
from areas of low liability to areas 
where damage and costs will be much 
greater. A large proportion of the 
worst fires that have occurred on the 
national forests burned for more than 
12 hours before they were attacked, 
and a considerable part of the total 
fire loss has been caused by such fires. 
For instance, nearly half of the total 
timber area burned during the five 
years studied, when the protective 
organization was not as well developed 
as it has subsequently become, is 
shown by the available records of 
elapsed time to have been burned over 
by fires which were not attacked until 
12 hours or more after their discoverv. 
(Tables XIV, XV, and XVI.) 
