Table 1.— Factors for adjusting treated bed burning rates for differences in untreated burning rates 



Pine needles 



Aspen excelsior 



Year 



Average 



Std. 

 dev. 



N 



Average 



Std. 



dev. 



Average 

 R/S 



Std. 



dev. 



N 



Average 

 R/W 



Std. 

 dev. 



N 



Ft/min 



g/min 



Ft/min 



g/mln 



1980 

 1970 



Difference 



2.03 

 1.81 

 0.22 



0.10 

 .03 



4 



12 



345 

 294 



51 



3.0 

 3.3 



4 

 11 



4.26 

 4.04 



0.22 



0.10 

 .14 



529 

 459 

 70 



35.1 

 6.1 



0.22 

 ^ - 2:03 = ° 



51 

 345 



= 0.852 



1 - 



0.22 

 42Q 



0.948 



70 



529 



= 0.868 



Adjustment 



0.892 



0.852 



0.948 



0.868 



'R/S = flame spread rate. 



^R/W = burning fuel rate of weight loss. 



Chemical Application 



A pressurized sprayer with a fan-shaped spray pattern was 

 used to apply retardant (George and Blakely 1972). The sprayer 

 was calibrated for each different retardant chemical and con- 

 centration to produce a spray pattern that would coat the fuels 

 uniformly. The volume of chemical solution applied to each 

 bed was held as closely as practical to 0.26 gal (1 liter), and the 

 different levels of the dried chemical applied to different beds 

 were varied by adjusting the solution concentrations. After 

 treatment, fuel beds were dried under environmental conditions 

 of 90° F ± 2° (32.2° C ± 2°), and 20 percent relative humid- 

 ity ± 2 percent, until all the solution water had been 

 evaporated and the fuel moisture content was about the same 

 as before treatment. Low-velocity fans were used to keep air 

 moving above the treated beds so drying would occur uni- 

 formly throughout the depth of the bed. After all the water 

 had evaporated (determined by frequent weighing on an elec- 

 tronic balance), beds were burned in a wind tunnel under con- 

 ditions of 90° F (32.2°), 20 percent relative humidity, and in a 

 5-mi/h (8-km/h) wind. (These environmental conditions can be 

 related to wildfire situations by the following: When needles 

 and excelsior are classed as fuel type U, the National Fire- 

 Danger Rating System [NFDRS] grades fires in untreated fuels 

 as spread component 5, energy release rate 38, and burning in- 

 dex 34.) 



Burning Procedures 



A 3-ft- (0.91-m-) long untreated fuel bed of the same fuel 

 type and loading as that in the treated bed was ignited and 

 allowed to bum into the treated fuel. As the fuel burned, the 

 rate of weight loss was continuously measured by four load 

 cells mounted beneath the bed (George and Blakely 1970), and 

 data were recorded on a Tektronix® 4051 microcomputer. The 

 flame spread was monitored visually, and an event marker was 

 used to record the flame front progress. After each fire, the 

 recorded data were entered into a computer program, and 

 flame spread rate and total fuel bed weight loss rate were calcu- 

 lated and plotted. These two parameters were used for compar- 

 ing the effectiveness of different chemicals and treatment levels. 



RESULTS 



About 250 treated and untreated beds were burned. Results 

 of burning pine needles and aspen excelsior treated with DAP 

 have been reported previously (George and Blakely 1972), and 

 are used as a standard for USDA Fire Retardant Qualification 

 Tests. The M-MAP-treated beds were burned during the same 

 period as DAP-treated beds (George and Blakely 1972), and 

 therefore untreated ponderosa pine and aspen excelsior from 

 the same untreated fuel batches were used. (The M-MAP data 

 have not been published previously.) The remaining fires were ■ 

 conducted using untreated fuels collected several years later. 

 Adjustments were made (table 1) in the data for recent bums 

 to compensate for differences in untreated buming rates. 

 Tables for all MAP-treated (except M-MAP) beds contain col- 

 umns of adjusted spread- and weight-loss rates that were used 

 for regression analysis. These data and those for DAP and 

 M-MAP are shown in tables 2 through 9. 



3 



