Retardants and Smoke Production 



Laboratory studies have shown that some 

 retardants, such as diammonium phosphate 

 (DAP), apparently polymerize the tars. 2 

 These polymerized tars might lead to the in- 

 crease in smoke. For example, Eickner and 

 Schaffer 3 found that the most effective fire 

 retardant chemicals, DAP and ZnCi 2 , greatly 

 increased smoke production in tests on 



Douglas-fir plywood. Other chemicals tested 

 showed a decrease in smoke density. They al- 

 so found that chemicals previously suspected 

 of promoting postglowing reactions, such as 

 sodium dichromate and ammonium sulfate, 

 also reduced smoke index values. Similar re- 

 sults using particle board were reported by 

 Syska. 4 



Diammonium Phosphate and Ammonium Sulfate 



The flame retarding effects of DAP and 

 ammonium sulfate (AS) on rate of spread and 

 intensity for wood and fine fuel fires have 

 been tested under controlled conditions. 5 

 Findings show DAP to be most effective in 

 slowing spread and reducing intensity. Two 

 other differences between DAP and AS are 

 apparent. The residue remaining after the 

 tests is always much less from the AS treat- 



2 Thermo gravimetric data on file at the Northern 

 Forest Fire Laboratory, Missoula, Montana. 



3 H. W. Eickner and E. L. Schaffer. Fire-retardant 

 effects of individual chemicals on Douglas-fir ply- 

 wood. Fire Technol. 3: 90-104, illus. 1967. 



ment. For example, the residue from AS 

 treated excelsior fuel usually is close to non- 

 existent (fig. 1). The other difference is the 

 tremendous amount of black smoke produced 

 by DAP treatment as compared to the much 

 smaller amount of whitish smoke produced 

 by the AS treatment. 



Arthur D. Syska. Exploratory investigation of 

 fire-retardant treatments for particle board. USD A 

 Forest Serv. Res. Note FPL-0201, 32 p. 1969. 



5 Charles W. George and Aylmer D. Blakely. Effects 

 of ammonium sulfate and ammonium phosphate on 

 flammability. USD A Forest Serv., Intermountain For- 

 est and Range Exp. Station, Ogden, Utah (in prepara- 

 tion). 



2 



