2.0 r 



1.8 



1.6 



1.4 



t 1.2 



a 

 < 



u 

 ot 

 a. 



w 1.0 



< 



< 



0.8 



0.6 



0.4 



0.2 



Figure 12. - -In- 

 fluence of con- 

 centration and 

 dryness upon 

 rate of spread 

 of long-term 

 retardant . 



_L 



30 35 40 45 50 55 60 



EQUIVALENT NATIONAL SPREAD INDEX 



65 



7( 



4. The maximum length of time that a short-term retardant can effectively "hold" a fire 

 can be predicted by equation ( 7) : 



w f (.22-M f ) = 1.96 exp 



-0.0307 U(p Vo -p Vl )t 



This holding time may be extremely short when the retardant is subjected to low humidity, 

 moderate airflow, exposure to sunlight, and radiant or convective heating by flames. 



5. A certain minimum ratio, by weight, of long-term retardant to fuel appears necessary 

 for best results. Laboratory tests indicate the ratio is near 0.4. Ultimately this ratio will have 

 to be associated with actual weight of salt remaining instead of total weight of solution applied. 



26 



