Air 



sRetardant Solution^ 



Figure 1 . — Application 

 equipment. 



determining the volume rate through the nozzle at a given pressure while measuring the 

 lateral spray pattern. A nozzle diameter, height, and tank pressure were selected 

 that would provide a uniform lateral pattern over the fuel bed width. The fuel beds 

 were then pushed under the nozzle at a constant predetermined speed to apply the desired 

 amount of solution. The application equipment and spray system in operation are shown 

 in figures 1 and 2. 



The fuel beds were weighed prior to and following application of the retardant 

 solution. The amount of solution per square foot of fuel bed and the percent of solu- 

 tion as a function of dry fuel weight were calculated. 



Conditioning of Fuel and Environmental Conditions 



Following application of the retardant solution, the fuel beds were allowed to 

 reach an equilibrium moisture content in the combustion chamber under controlled 

 environmental conditions. The combustion chamber air temperature was held at 90° ±2° F. 

 and the relative humidity at 20 ±2 percent. A new equilibrium moisture content of 

 between 5.0 and 6.5 percent was reached. Equilibrium was determined by periodic weight 

 checks of the fuel bed, and the moisture content was determined by using the xylene 

 distillation method. 



All burning tests were made in a large wind tunnel at an air velocity of 5 m.p.h. 

 Fuel bed conditioning and the burning tests were conducted under similar temperature and 

 relative humidity conditions. These conditions are equivalent to a Fine Fuel Spread 

 Index of 36 (USDA Forest Service 1964). 



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