100 200 300 400 500 600 700 



Temperature ( C ) 



Figure 17. — Thermal decomposition curves for (NH^) 2 HPO^ and (NH^) 2 SOi i heated at 25° 



C./min. in a flow of 1 liter/min. air. 



ammonium sulfate would affect the glowing combustion process very little. Ammonium 

 phosphate, on the other hand, might still be present, altering glowing combustion as 

 well as flaming combustion. This would explain why these two chemicals affect glowing 

 combustion in different ways. This does not mean that the chemicals' effects are 

 necessarily different because of physical degradation differences. The difference may 

 be a chemical difference and still depend on the amount of chemical available to enter 

 into the reaction. 



Anderson (1969), using ponderosa pine needle fuel beds, similar to those of this 

 study, found the average temperature within the combustion zone to be 867° C. 

 Considering a reduction in these temperatures because of treatment and durational 

 differences between temperatures measured in the combustion zone and those determined 

 during thermal analysis, it is likely that most of the ammonium sulfate would decompose 

 during passage of the flame front. 



The effects other chemicals have on flammability can be evaluated by using the 

 regression equations which quantify the effects of ammonium phosphate and sulfate on 

 flammability. These relationships can be used as standards by which the effect of 

 typical forest fire retardant additives such as thickening agents, coloring agents, 

 and corrosion and spoilage inhibitors, can be judged. 



These data can also provide the basis for linking some of the more basic pyrolysis 

 and combustion data concerning the effects of fire retardant chemicals with actual 

 controlled open combustion laboratory tests. 



19 



