Table 1 . --Comparison of chemical characteristics of ponderosa pine needles 

 and aspen excelsior 





Aspen 



: Ponderosa pine 



I tem 



excelsior 



: needles 



Cellulose (percent dry weight) 



42.0 



18.0 



Ash content (percent dry weight) 



0.36 



3.87 



Silica-free ash (percent dry weight) 



0.36 



1.55 



Ether extractives (percent dry weight) 



<1.0 



9.73 



Heat content (B.t.u./lb.) 



8,485 



8,753 



Ponderosa pine needles for fuel beds were collected and cleaned during the year 

 prior to the tests. The needles were stored indoors until an equilibrium moisture 

 content was reached, and aspen excelsior which had been cut to specifications was given 

 similar treatment. Following this ambient indoor conditioning, moisture contents were 

 between 5 and 8.5 percent (percent of ovendry weight) for both types of fuel. 



Fuel beds, fuel bed configuration, and a method of preparation similar to that 

 used by Rothermel and Hardy (1965) was adopted for use in the study. A lighter fuel 

 loading was necessary for aspen excelsior because of its higher surface area-to-volume 

 ratio. Characteristics of the fuel bed are shown in table 2. 



Method of Chemical Application 



A method of application was developed and used to distribute the retardant solution 

 uniformly over the surface of the fuel bed at a constant depth of penetration. This 

 was accomplished by applying a constant volume of solution and varying only the concen- 

 tration or amount of the chemical in solution. The solution was contained in a pres- 

 surized supply tank that had a calibrated flow. The calibration was established by 



Table 2. --Fuel bed characteristics 



Fuel bed 

 (Inches) 



Average equilibrium 

 moisture content 



Loading at EMC 



Fuel surface-to- 

 volume ratio 



Fuel bed void 

 volume- to -surf ace- 

 to-area ratio 



Percent 



Lb. /bed Lb. /ft. 2 a ft. 2 /ft 3 



X ft} /ft 2 



Aspen excelsior 



3 by 18 by 36 1 

 3 by 18 by 96 



Ponderosa pine needles 



5 by 18 by 36 1 

 3 by 18 by 96 



7.0 

 7.0 



7.5 

 7.5 



1.5 

 4.0 



2.25 

 6.0 



0.33 

 .33 



.50 

 .50 



1,848 

 1 ,848 



1,741 

 1,741 



9.36 by lO" 3 

 9.36 by 10" 3 



-3 



8.46 by 10 

 8.46 by 10" 3 



Igniter tray. 



4 



