Fire load:
An important factor in establishing the basis for the assessment of the fire risk pertaining to any building is the concept of ‘fire load’
quantity of heat liberated per unit area when a building and its contents are completely burnt.
which indicates the
All occupancies/buildings, occupancies/buildings, etc. can be graded according to their fire hazard and are to be provided for with suitable fire precautions on the basis of the fire load. Hence, grading of buildings according to both fire load and fire resistance can be made. he formula for calculating fire load is as stated. Fire load = (combustibles in kg) x calorific value in kcalkg Floor area in square meters !he calculation of the fire load is the basis for the determining the classification of the occupancies for the fire grading of buildings. Fire grading of the structures:
!tructural element of buildings are graded according to the the time factor which is nearly e"ual to but does not e#ceed the test period which the element fulfills its specified re"uirements. Accordingly, all structural elements have been graded under the following five categories depending upon their five resistance, viz.,
$rade %&&&&&&&& ' hours $rade (&&&&&&&& ) hours $rade *&&&&&&&& ( hours $rade )&&&&&&&& % hours $rade +&&&&&&&& .+ hours
"lassification of #ccupancies :
he fire offices committee -..0, in its report of fire grading of buildings in %1)', has recognized recognized * main classes classes of occupancies occupancies on the basis of the fire load. his also conforms to the relevant 2.!. specifications and may be stated as3 #ccupancies of low fire load: ordinary buildings for residential purposes, hotels, offices, schools, etc, or occupancies having a fire load not e#ceeding (,4+, kcal/s".mtr of net floor area of any compartment, nor e#ceeding an average of++, kcal/s".mtr on a limited isolated area. -for reference, the ma#imum for this type in 5.6.!. system is %,, 7.h./s".ft0
he fire resistance re"uired by buildings of this category to withstand the complete burn8out of their contents without collapse is % hour as has been found after tests. 9#tensive investigations carried out in !witzerland and $ermany have shown that the fire load in offices offices varies from % kg to * kg/s".mtr wood e"uivalent e"uivalent to )*,*+' to %*,': kcal/s".mtr where as this type of occupancy has an one hour rating with ma#imum fire loading upto (4,14: kcal/s".mtr e"uivalent to ' kg/s".m. #ccupancies of moderate low fire load: ;etail shops, bazaars, stalls, factories, etc. hence the fire load e#ceeds, (,4+, kcal/s".mtr, and is upto ++, kcal/s".mtr.
his is e"uivalent to the fire load of (,4+, kcal/s".mtr, not e#ceeding an average of %,%, kcal/s".mtr on limited isolated area as per relevant 2.!. specifications.
#ccupancies of high low fire load: $odowns, warehouses, etc. this category as per 2.!. specifications e#ceeds the fire load by ++, kcal/s".mtr, kcal/s".mtr, but does not e#ceed e#ceed an average of %,%, kcal/s".mtr of floor area. A fire resistance of ) hours for these types of occupancies is considered sufficient. sufficient.
-for reference, the ma#imum for this type in 5.6.!. system is ),, 7.h./s".ft e#ceeding an average of (,, 7.h./s".ft0.
$xample: he manufacturing manufacturing process industry uses the following material. =alculate the 5ire load by using the following data3 >ateria rial
?uantity in kg.
Area in s".mtr
6aper ood =oal ;ubber 6aetroleum product
% (, %, + +,
% ( + (+ *
Bote3 % calorie C ).%: @oule
=alorific value -k@/kg0 %+' %4+ ( ) )*
Fire load = (combustibles in kg) x calorific value in kcalkg Floor area in square meters
5ire load -paper0 D % # *4*(.+ *4*(.+ D *4*(+.4) *4*(+.4) kcal/s".mt % 5ire load -wood0 D ( # )%:'.'( D )%:'( kcal/s".mt ( 5ire load load -coal0 -coal0 D %, # )4:).':: D 1+'1*44.11 1+'1*44.11 kcal/s".mt kcal/s".mt + 5ire load -rubber0 D + # 1+'1.*4 D %1%*:4) kcal/s".mt kcal/s".mt (+ 5ire load -6etroleum products0 D +, # %(:4.:% D %4%)+%*+.+4 * kcal/s".mt otal fire load D (1)(%1+.* kcal/s".mt ;esult indicates that the occupancy has High fire load. !o fire resistance should be of ) hours.
%nstallation of fire extinguishers: $xample:
-%0 Eetermine the number of fire e#tinguishers re"uired to give ade"uate protection for a given property. ;isk3 Fight engineering workshop -Fight hazard0 Area3 *%+m # %%( m. i.e. *+,(: s". mtr. ype of hazard3 =lass ‘A’ fire due to normal combustibles. As per 2! (%1 this is Fight Hazard so one 1 ltr water e#pelling e#tinguisher for every ' s".mtr of floor area should be installed. 9#tinguisher should be available available within within (+ mtr radius.
Here otal area is *+,(: s".mt. !o no. of e#tinguisher D *+,(: s".mt . D +:.: ' so no. of e#tinguisher re"uired is +1.
-(0 Eetermine the number of fire e#tinguishers re"uired to give ade"uate protection for a given property. ;isk3 6etroleum 6etroleum processing processing units -High hazard0 Area3 *m # %+ m. i.e. )+ s". s". mtr.
ype of hazard3 =lass ‘7’ fire due to petroleum products. As per 2! (%1 this is High High Hazard so two 1 ltr foam chemical/mechanical chemical/mechanical typeG or + kg capacity dry powder e#tinguisher for every ' s".mtr with minimum of four e#tinguisher per compartment shall be installed. 9#tinguisher should be available available within within %+ mtr radius. Here otal area is )+ s".mt. !o no. of e#tinguisher D )+ s".mt . D 4+ ' so no. of e#tinguisher re"uired is 4+.
