RESULTS 



Treatment Effect on Thermal Variables 



The effect of the retardants on the burning 

 characteristics of the crib fires is quite appar- 

 ent. Both AS and DAP lowered the maximum 

 weight loss rate, flame height, and radiant 

 energy output. The effect of DAP treatment 

 level on weight loss rate is shown in figure 3 

 and that for AS level is shown in figure 4. As 

 can be seen, the increase in treatment level 

 lowers the weight loss rate and increases the 

 time to reach maximum intensity. Treatment 

 level refers to the percent of chemical on the 

 cribs, excluding the 4 by 4's. The graphs of 

 the equations for treatment against maximum 



radiation are shown in figures 5 and 6. The 

 DAP treatments are most effective in both 

 cases. The difference between types of chemi- 

 cals is significant at the 99 percent level as 

 determined by the F test (table 2). 



The sequential photographs in figure 7 

 clearly show the effects of the two chemicals 

 on intensity: buildup time is increased and 

 the intensity is decreased (indicated by flame 

 size); DAP was the most effective. Figure 8 

 shows the three fires at the time of maximum 

 intensity and the residue left following active 

 combustion. 



Effect on Residue 



The residue remaining following the fire 

 was related to the type of treatment (fig. 9). 

 The total residue and DAP treatment level 

 had a correlation coefficient R 2 of 0.87; the 

 R 2 for AS was 0.21. However, the effects of 



the two types of treatment were statistically 

 different at the 99 percent level. The residue 

 from the 4 by 4's alone was found not to be 

 significant, both within and between types of 

 treatments. 



2000 



1476% 



12 16 20 24 

 Elapsed time (min ) 



28 



32 



36 



2000 



11.94% 



12 16 20 24 28 

 Elapsed time (mm ) 



Figure 3. — Weight loss rates relative to time Figure 4. — Weight loss rates relative to time 

 for several levels of DAP treatment. for several levels of AS treatment. 



7 



